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<pre>Network Working Group                                          D. Pinkas
Request for Comments: 5126                                      Bull SAS
Obsoletes: <a href="./rfc3126">3126</a>                                                  N. Pope
Category: Informational                                 Thales eSecurity
                                                                 J. Ross
                                                  Security and Standards
                                                           February 2008


               <span class="h1">CMS Advanced Electronic Signatures (CAdES)</span>

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Abstract

   This document defines the format of an electronic signature that can
   remain valid over long periods.  This includes evidence as to its
   validity even if the signer or verifying party later attempts to deny
   (i.e., repudiates) the validity of the signature.

   The format can be considered as an extension to <a href="./rfc3852">RFC 3852</a> and <a href="./rfc2634">RFC</a>
   <a href="./rfc2634">2634</a>, where, when appropriate, additional signed and unsigned
   attributes have been defined.

   The contents of this Informational RFC amount to a transposition of
   the ETSI Technical Specification (TS) 101 733 V.1.7.4 (CMS Advanced
   Electronic Signatures -- CAdES) and is technically equivalent to it.

   The technical contents of this specification are maintained by ETSI.
   The ETSI TS and further updates are available free of charge at:
   <a href="http://www.etsi.org/WebSite/Standards/StandardsDownload.aspx">http://www.etsi.org/WebSite/Standards/StandardsDownload.aspx</a>
















<span class="grey">Pinkas, et al.               Informational                      [Page 1]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-2" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


Table of Contents

   <a href="#section-1">1</a>. Introduction ....................................................<a href="#page-6">6</a>
   <a href="#section-2">2</a>. Scope ...........................................................<a href="#page-6">6</a>
   <a href="#section-3">3</a>. Definitions and Abbreviations ...................................<a href="#page-8">8</a>
      <a href="#section-3.1">3.1</a>. Definitions ................................................<a href="#page-8">8</a>
      <a href="#section-3.2">3.2</a>. Abbreviations .............................................<a href="#page-11">11</a>
   <a href="#section-4">4</a>. Overview .......................................................<a href="#page-12">12</a>
      <a href="#section-4.1">4.1</a>. Major Parties .............................................<a href="#page-13">13</a>
      <a href="#section-4.2">4.2</a>. Signature Policies ........................................<a href="#page-14">14</a>
      <a href="#section-4.3">4.3</a>. Electronic Signature Formats ..............................<a href="#page-15">15</a>
           <a href="#section-4.3.1">4.3.1</a>. CAdES Basic Electronic Signature (CAdES-BES) .......<a href="#page-15">15</a>
           4.3.2. CAdES Explicit Policy-based Electronic
                  Signatures (CAdES-EPES) ............................<a href="#page-18">18</a>
      <a href="#section-4.4">4.4</a>. Electronic Signature Formats with Validation Data .........<a href="#page-19">19</a>
           <a href="#section-4.4.1">4.4.1</a>. Electronic Signature with Time (CAdES-T) ...........<a href="#page-20">20</a>
           4.4.2. ES with Complete Validation Data References
                  (CAdES-C) ..........................................<a href="#page-21">21</a>
           <a href="#section-4.4.3">4.4.3</a>. Extended Electronic Signature Formats ..............<a href="#page-23">23</a>
                  4.4.3.1. EXtended Long Electronic Signature
                           (CAdES-X Long) ............................<a href="#page-24">24</a>
                  4.4.3.2. EXtended Electronic Signature with
                           Time Type 1 ...............................<a href="#page-25">25</a>
                  4.4.3.3. EXtended Electronic Signature with
                           Time Type 2 ...............................<a href="#page-26">26</a>
                  4.4.3.4. EXtended Long Electronic Signature
                           with Time (CAdES-X Long ...................<a href="#page-27">27</a>
           <a href="#section-4.4.4">4.4.4</a>. Archival Electronic Signature (CAdES-A) ............<a href="#page-27">27</a>
      <a href="#section-4.5">4.5</a>. Arbitration ...............................................<a href="#page-28">28</a>
      <a href="#section-4.6">4.6</a>. Validation Process ........................................<a href="#page-29">29</a>
   <a href="#section-5">5</a>. Electronic Signature Attributes ................................<a href="#page-30">30</a>
      <a href="#section-5.1">5.1</a>. General Syntax ............................................<a href="#page-30">30</a>
      <a href="#section-5.2">5.2</a>. Data Content Type .........................................<a href="#page-30">30</a>
      <a href="#section-5.3">5.3</a>. Signed-data Content Type ..................................<a href="#page-30">30</a>
      <a href="#section-5.4">5.4</a>. SignedData Type ...........................................<a href="#page-31">31</a>
      <a href="#section-5.5">5.5</a>. EncapsulatedContentInfo Type ..............................<a href="#page-31">31</a>
      <a href="#section-5.6">5.6</a>. SignerInfo Type ...........................................<a href="#page-31">31</a>
           <a href="#section-5.6.1">5.6.1</a>. Message Digest Calculation Process .................<a href="#page-32">32</a>
           <a href="#section-5.6.2">5.6.2</a>. Message Signature Generation Process ...............<a href="#page-32">32</a>
           <a href="#section-5.6.3">5.6.3</a>. Message Signature Verification Process .............<a href="#page-32">32</a>
      <a href="#section-5.7">5.7</a>. Basic ES Mandatory Present Attributes .....................<a href="#page-32">32</a>
           <a href="#section-5.7.1">5.7.1</a>. content-type .......................................<a href="#page-32">32</a>
           <a href="#section-5.7.2">5.7.2</a>. Message Digest .....................................<a href="#page-33">33</a>
           <a href="#section-5.7.3">5.7.3</a>. Signing Certificate Reference Attributes ...........<a href="#page-33">33</a>
                  5.7.3.1. ESS signing-certificate Attribute
                           Definition ................................<a href="#page-34">34</a>
                  5.7.3.2. ESS signing-certificate-v2
                           Attribute Definition ......................<a href="#page-34">34</a>



<span class="grey">Pinkas, et al.               Informational                      [Page 2]</span></pre>
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<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


                  5.7.3.3. Other signing-certificate
                           Attribute Definition ......................<a href="#page-35">35</a>
      5.8. Additional Mandatory Attributes for Explicit
           Policy-based Electronic Signatures ........................<a href="#page-36">36</a>
           <a href="#section-5.8.1">5.8.1</a>. signature-policy-identifier ........................<a href="#page-36">36</a>
      <a href="#section-5.9">5.9</a>. CMS Imported Optional Attributes ..........................<a href="#page-38">38</a>
           <a href="#section-5.9.1">5.9.1</a>. signing-time .......................................<a href="#page-38">38</a>
           <a href="#section-5.9.2">5.9.2</a>. countersignature ...................................<a href="#page-39">39</a>
      <a href="#section-5.10">5.10</a>. ESS-Imported Optional Attributes .........................<a href="#page-39">39</a>
           <a href="#section-5.10.1">5.10.1</a>. content-reference Attribute .......................<a href="#page-39">39</a>
           <a href="#section-5.10.2">5.10.2</a>. content-identifier Attribute ......................<a href="#page-39">39</a>
           <a href="#section-5.10.3">5.10.3</a>. content-hints Attribute ...........................<a href="#page-40">40</a>
      5.11. Additional Optional Attributes Defined in the
            Present Document .........................................<a href="#page-40">40</a>
           <a href="#section-5.11.1">5.11.1</a>. commitment-type-indication Attribute ..............<a href="#page-41">41</a>
           <a href="#section-5.11.2">5.11.2</a>. signer-location Attribute .........................<a href="#page-43">43</a>
           <a href="#section-5.11.3">5.11.3</a>. signer-attributes Attribute .......................<a href="#page-43">43</a>
           <a href="#section-5.11.4">5.11.4</a>. content-time-stamp Attribute ......................<a href="#page-44">44</a>
      <a href="#section-5.12">5.12</a>. Support for Multiple Signatures ..........................<a href="#page-44">44</a>
           <a href="#section-5.12.1">5.12.1</a>. Independent Signatures ............................<a href="#page-44">44</a>
           <a href="#section-5.12.2">5.12.2</a>. Embedded Signatures ...............................<a href="#page-45">45</a>
   <a href="#section-6">6</a>. Additional Electronic Signature Validation Attributes ..........<a href="#page-45">45</a>
      <a href="#section-6.1">6.1</a>. signature time-stamp Attribute (CAdES-T) ..................<a href="#page-47">47</a>
           <a href="#section-6.1.1">6.1.1</a>. signature-time-stamp Attribute Definition ..........<a href="#page-47">47</a>
      <a href="#section-6.2">6.2</a>. Complete Validation Data References (CAdES-C) .............<a href="#page-48">48</a>
           6.2.1. complete-certificate-references Attribute
                  Definition .........................................<a href="#page-48">48</a>
           6.2.2. complete-revocation-references Attribute
                  Definition .........................................<a href="#page-49">49</a>
           6.2.3. attribute-certificate-references Attribute
                  Definition .........................................<a href="#page-51">51</a>
           6.2.4. attribute-revocation-references Attribute
                  Definition .........................................<a href="#page-52">52</a>
      <a href="#section-6.3">6.3</a>. Extended Validation Data (CAdES-X) ........................<a href="#page-52">52</a>
           6.3.1. Time-Stamped Validation Data (CAdES-X Type
                  <a href="#section-1">1</a> or Type 2) .......................................<a href="#page-53">53</a>
           6.3.2. Long Validation Data (CAdES-X Long, CAdES-X
                  Long Type 1 or 2) ..................................<a href="#page-53">53</a>
           <a href="#section-6.3.3">6.3.3</a>. certificate-values Attribute Definition ............<a href="#page-54">54</a>
           <a href="#section-6.3.4">6.3.4</a>. revocation-values Attribute Definition .............<a href="#page-54">54</a>
           <a href="#section-6.3.5">6.3.5</a>. CAdES-C-time-stamp Attribute Definition ............<a href="#page-56">56</a>
           6.3.6. time-stamped-certs-crls-references
                  Attribute Definition ...............................<a href="#page-57">57</a>
      <a href="#section-6.4">6.4</a>. Archive Validation Data ...................................<a href="#page-58">58</a>
           <a href="#section-6.4.1">6.4.1</a>. archive-time-stamp Attribute Definition ............<a href="#page-58">58</a>
   <a href="#section-7">7</a>. Other Standard Data Structures .................................<a href="#page-60">60</a>
      <a href="#section-7.1">7.1</a>. Public Key Certificate Format .............................<a href="#page-60">60</a>
      <a href="#section-7.2">7.2</a>. Certificate Revocation List Format ........................<a href="#page-60">60</a>



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<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


      <a href="#section-7.3">7.3</a>. OCSP Response Format ......................................<a href="#page-60">60</a>
      <a href="#section-7.4">7.4</a>. Time-Stamp Token Format ...................................<a href="#page-60">60</a>
      <a href="#section-7.5">7.5</a>. Name and Attribute Formats ................................<a href="#page-60">60</a>
      <a href="#section-7.6">7.6</a>. AttributeCertificate ......................................<a href="#page-61">61</a>
   <a href="#section-8">8</a>. Conformance Requirements .......................................<a href="#page-61">61</a>
      <a href="#section-8.1">8.1</a>. CAdES-Basic Electronic Signature (CAdES-BES) ..............<a href="#page-62">62</a>
      <a href="#section-8.2">8.2</a>. CAdES-Explicit Policy-based Electronic Signature ..........<a href="#page-63">63</a>
      <a href="#section-8.3">8.3</a>. Verification Using Time-Stamping ..........................<a href="#page-63">63</a>
      <a href="#section-8.4">8.4</a>. Verification Using Secure Records .........................<a href="#page-63">63</a>
   <a href="#section-9">9</a>. References .....................................................<a href="#page-64">64</a>
      <a href="#section-9.1">9.1</a>. Normative References ......................................<a href="#page-64">64</a>
      <a href="#section-9.2">9.2</a>. Informative References ....................................<a href="#page-65">65</a>
   Annex A (normative): ASN.1 Definitions ............................<a href="#page-69">69</a>
           A.1. Signature Format Definitions Using
                <a href="#appendix-X.208">X.208</a> ASN.1 Syntax ...................................<a href="#page-69">69</a>
           A.2. Signature Format Definitions Using
                <a href="#appendix-X.680">X.680</a> ASN.1 Syntax ...................................<a href="#page-77">77</a>
   Annex B (informative): Extended Forms of Electronic Signatures ....<a href="#page-86">86</a>
           <a href="#appendix-B.1">B.1</a>. Extended Forms of Validation Data ....................<a href="#page-86">86</a>
                <a href="#appendix-B.1.1">B.1.1</a>. CAdES-X Long ..................................<a href="#page-87">87</a>
                <a href="#appendix-B.1.2">B.1.2</a>. CAdES-X Type 1 ................................<a href="#page-88">88</a>
                <a href="#appendix-B.1.3">B.1.3</a>. CAdES-X Type 2 ................................<a href="#page-90">90</a>
                <a href="#appendix-B.1.4">B.1.4</a>. CAdES-X Long Type 1 and CAdES-X Long Type 2 ...<a href="#page-91">91</a>
           <a href="#appendix-B.2">B.2</a>. Time-Stamp Extensions ................................<a href="#page-93">93</a>
           <a href="#appendix-B.3">B.3</a>. Archive Validation Data (CAdES-A) ....................<a href="#page-94">94</a>
           <a href="#appendix-B.4">B.4</a>. Example Validation Sequence ..........................<a href="#page-97">97</a>
           <a href="#appendix-B.5">B.5</a>. Additional Optional Features ........................<a href="#page-102">102</a>
   Annex C (informative): General Description .......................<a href="#page-103">103</a>
           <a href="#appendix-C.1">C.1</a>. The Signature Policy ................................<a href="#page-103">103</a>
           <a href="#appendix-C.2">C.2</a>. Signed Information ..................................<a href="#page-104">104</a>
           <a href="#appendix-C.3">C.3</a>. Components of an Electronic Signature ...............<a href="#page-104">104</a>
                <a href="#appendix-C.3.1">C.3.1</a>. Reference to the Signature Policy ............<a href="#page-104">104</a>
                <a href="#appendix-C.3.2">C.3.2</a>. Commitment Type Indication ...................<a href="#page-105">105</a>
                <a href="#appendix-C.3.3">C.3.3</a>. Certificate Identifier from the Signer .......<a href="#page-106">106</a>
                <a href="#appendix-C.3.4">C.3.4</a>. Role Attributes ..............................<a href="#page-106">106</a>
                       <a href="#appendix-C.3.4.1">C.3.4.1</a>.  Claimed Role .......................<a href="#page-107">107</a>
                       <a href="#appendix-C.3.4.2">C.3.4.2</a>.  Certified Role .....................<a href="#page-107">107</a>
                <a href="#appendix-C.3.5">C.3.5</a>. Signer Location ..............................<a href="#page-108">108</a>
                <a href="#appendix-C.3.6">C.3.6</a>. Signing Time .................................<a href="#page-108">108</a>
                <a href="#appendix-C.3.7">C.3.7</a>. Content Format ...............................<a href="#page-108">108</a>
                <a href="#appendix-C.3.8">C.3.8</a>. content-hints ................................<a href="#page-109">109</a>
                <a href="#appendix-C.3.9">C.3.9</a>. Content Cross-Referencing ....................<a href="#page-109">109</a>
           <a href="#appendix-C.4">C.4</a>. Components of Validation Data .......................<a href="#page-109">109</a>
                <a href="#appendix-C.4.1">C.4.1</a>. Revocation Status Information ................<a href="#page-109">109</a>
                       <a href="#appendix-C.4.1.1">C.4.1.1</a>. CRL Information .....................<a href="#page-110">110</a>
                       <a href="#appendix-C.4.1.2">C.4.1.2</a>. OCSP Information ....................<a href="#page-110">110</a>
                <a href="#appendix-C.4.2">C.4.2</a>. Certification Path ...........................<a href="#page-111">111</a>
                <a href="#appendix-C.4.3">C.4.3</a>. Time-stamping for Long Life of Signatures ....<a href="#page-111">111</a>



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<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


                C.4.4. Time-stamping for Long Life of Signature
                       before CA key Compromises ....................<a href="#page-113">113</a>
                        C.4.4.1. Time-stamping the ES with
                                 Complete Validation Data ...........<a href="#page-113">113</a>
                        C.4.4.2. Time-Stamping Certificates and
                                 Revocation Information References ..114
                <a href="#appendix-C.4.5">C.4.5</a>. Time-stamping for Archive of Signature .......<a href="#page-115">115</a>
                <a href="#appendix-C.4.6">C.4.6</a>. Reference to Additional Data .................<a href="#page-116">116</a>
                <a href="#appendix-C.4.7">C.4.7</a>. Time-Stamping for Mutual Recognition .........<a href="#page-116">116</a>
                <a href="#appendix-C.4.8">C.4.8</a>. TSA Key Compromise ...........................<a href="#page-117">117</a>
           <a href="#appendix-C.5">C.5</a>. Multiple Signatures .................................<a href="#page-118">118</a>
   Annex D (informative): Data Protocols to Interoperate with TSPs ..118
           <a href="#appendix-D.1">D.1</a>. Operational Protocols ...............................<a href="#page-118">118</a>
                <a href="#appendix-D.1.1">D.1.1</a>. Certificate Retrieval ........................<a href="#page-118">118</a>
                <a href="#appendix-D.1.2">D.1.2</a>. CRL Retrieval ................................<a href="#page-118">118</a>
                <a href="#appendix-D.1.3">D.1.3</a>. Online Certificate Status ....................<a href="#page-119">119</a>
                <a href="#appendix-D.1.4">D.1.4</a>. Time-Stamping ................................<a href="#page-119">119</a>
           <a href="#appendix-D.2">D.2</a>. Management Protocols ................................<a href="#page-119">119</a>
                <a href="#appendix-D.2.1">D.2.1</a>. Request for Certificate Revocation ...........<a href="#page-119">119</a>
   Annex E (informative): Security Considerations ...................<a href="#page-119">119</a>
           <a href="#appendix-E.1">E.1</a>. Protection of Private Key ...........................<a href="#page-119">119</a>
           <a href="#appendix-E.2">E.2</a>. Choice of Algorithms ................................<a href="#page-119">119</a>
   Annex F (informative): Example Structured Contents and MIME ......<a href="#page-120">120</a>
           <a href="#appendix-F.1">F.1</a>. General Description .................................<a href="#page-120">120</a>
                <a href="#appendix-F.1.1">F.1.1</a>. Header Information ...........................<a href="#page-120">120</a>
                <a href="#appendix-F.1.2">F.1.2</a>. Content Encoding .............................<a href="#page-121">121</a>
                <a href="#appendix-F.1.3">F.1.3</a>. Multi-Part Content ...........................<a href="#page-121">121</a>
           <a href="#appendix-F.2">F.2</a>. S/MIME ..............................................<a href="#page-122">122</a>
                <a href="#appendix-F.2.1">F.2.1</a>. Using application/pkcs7-mime .................<a href="#page-123">123</a>
                <a href="#appendix-F.2.2">F.2.2</a>. Using application/pkcs7-signature ............<a href="#page-124">124</a>
   Annex G (informative): Relationship to the European Directive
                          and EESSI .................................<a href="#page-125">125</a>
           <a href="#appendix-G.1">G.1</a>. Introduction ........................................<a href="#page-125">125</a>
           <a href="#appendix-G.2">G.2</a>. Electronic Signatures and the Directive .............<a href="#page-126">126</a>
           G.3. ETSI Electronic Signature Formats and the Directive .127
           G.4. EESSI Standards and Classes of Electronic Signature .127
                <a href="#appendix-G.4.1">G.4.1</a>. Structure of EESSI Standardization ...........<a href="#page-127">127</a>
                <a href="#appendix-G.4.2">G.4.2</a>. Classes of Electronic Signatures .............<a href="#page-128">128</a>
                G.4.3. Electronic Signature Classes and the ETSI
                       Electronic Signature Format ..................<a href="#page-128">128</a>
   Annex H (informative): APIs for the Generation and Verification
                          of Electronic Signatures Tokens ...........<a href="#page-129">129</a>
           <a href="#appendix-H.1">H.1</a>. Data Framing ........................................<a href="#page-129">129</a>
           <a href="#appendix-H.2">H.2</a>. IDUP-GSS-APIs Defined by the IETF ...................<a href="#page-131">131</a>
           <a href="#appendix-H.3">H.3</a>. CORBA Security Interfaces Defined by the OMG ........<a href="#page-132">132</a>
   Annex I (informative): Cryptographic Algorithms ..................<a href="#page-133">133</a>
           <a href="#appendix-I.1">I.1</a>. Digest Algorithms ...................................<a href="#page-133">133</a>
                <a href="#appendix-I.1.1">I.1.1</a>. SHA-1 ........................................<a href="#page-133">133</a>



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<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


                <a href="#appendix-I.1.2">I.1.2</a>. General ......................................<a href="#page-133">133</a>
           <a href="#appendix-I.2">I.2</a>. Digital Signature Algorithms ........................<a href="#page-134">134</a>
                <a href="#appendix-I.2.1">I.2.1</a>. DSA ..........................................<a href="#page-134">134</a>
                <a href="#appendix-I.2.2">I.2.2</a>. RSA ..........................................<a href="#page-135">135</a>
                <a href="#appendix-I.2.3">I.2.3</a>. General ......................................<a href="#page-135">135</a>
   Annex J (informative): Guidance on Naming ........................<a href="#page-137">137</a>
           <a href="#appendix-J.1">J.1</a>. Allocation of Names .................................<a href="#page-137">137</a>
           <a href="#appendix-J.2">J.2</a>. Providing Access to Registration Information ........<a href="#page-138">138</a>
           <a href="#appendix-J.3">J.3</a>. Naming Schemes ......................................<a href="#page-138">138</a>
                <a href="#appendix-J.3.1">J.3.1</a>. Naming Schemes for Individual Citizens .......<a href="#page-138">138</a>
                J.3.2. Naming Schemes for Employees of an
                       Organization .................................<a href="#page-139">139</a>

<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>.  Introduction</span>

   This document is intended to cover electronic signatures for various
   types of transactions, including business transactions (e.g.,
   purchase requisition, contract, and invoice applications) where
   long-term validity of such signatures is important.  This includes
   evidence as to its validity even if the signer or verifying party
   later attempts to deny (i.e., repudiates; see ISO/IEC 10181-5
   [<a href="#ref-ISO10181-5">ISO10181-5</a>]) the validity of the signature.

   Thus, the present document can be used for any transaction between an
   individual and a company, between two companies, between an
   individual and a governmental body, etc.  The present document is
   independent of any environment; it can be applied to any environment,
   e.g., smart cards, Global System for Mobile Communication Subscriber
   Identity Module (GSM SIM) cards, special programs for electronic
   signatures, etc.

   The European Directive on a community framework for Electronic
   Signatures defines an electronic signature as: "Data in electronic
   form which is attached to or logically associated with other
   electronic data and which serves as a method of authentication".

   An electronic signature, as used in the present document, is a form
   of advanced electronic signature, as defined in the Directive.

<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>.  Scope</span>

   The scope of the present document covers electronic signature formats
   only.  The aspects of Electronic Signature Policies are defined in
   <a href="./rfc3125">RFC 3125</a> [<a href="./rfc3125" title="&quot;Electronic Signature Policies&quot;">RFC3125</a>] and ETSI TR 102 272 [<a href="#ref-TR102272" title="&quot;Electronic Signatures and Infrastructures (ESI); ASN.1 format for signature policies&quot;">TR102272</a>].

   The present document defines a number of electronic signature
   formats, including electronic signatures that can remain valid over
   long periods.  This includes evidence as to its validity even if the



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   signer or verifying party later attempts to deny (repudiates) the
   validity of the electronic signature.

   The present document specifies use of Trusted Service Providers
   (e.g., Time-Stamping Authorities) and the data that needs to be
   archived (e.g., cross-certificates and revocation lists) to meet the
   requirements of long-term electronic signatures.

   An electronic signature, as defined by the present document, can be
   used for arbitration in case of a dispute between the signer and
   verifier, which may occur at some later time, even years later.

   The present document includes the concept of signature policies that
   can be used to establish technical consistency when validating
   electronic signatures, but it does not mandate their use.

   The present document is based on the use of public key cryptography
   to produce digital signatures, supported by public key certificates.
   The present document also specifies the use of time-stamping and
   time-marking services to prove the validity of a signature long after
   the normal lifetime of critical elements of an electronic signature.
   This document also, as an option, defines ways to provide very
   long-term protection against key compromise or weakened algorithms.

   The present document builds on existing standards that are widely
   adopted.  These include:

      - <a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]: "Cryptographic Message Syntax (CMS)";

      - ISO/IEC 9594-8/ITU-T Recommendation X.509 [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>]: "Information
        technology - Open Systems Interconnection - The Directory:
        Authentication framework";

      - <a href="./rfc3280">RFC 3280</a> [<a href="#ref-2" title="&quot;Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile&quot;">2</a>]: "Internet X.509 Public Key Infrastructure (PKIX)
        Certificate and Certificate Revocation List (CRL) Profile";

      - <a href="./rfc3161">RFC 3161</a> [<a href="#ref-7" title="&quot;Internet X.509 Public Key Infrastructure Time-Stamp Protocol (TSP)&quot;">7</a>]: "Internet X.509 Public Key Infrastructure
        Time-Stamp Protocol (TSP)".

      NOTE: See <a href="#section-11">Section 11</a> for a full set of references.

   The present document describes formats for advanced electronic
   signatures using ASN.1 (Abstract Syntax Notation 1) [<a href="#ref-14" title="&quot;Specification of Abstract Syntax Notation One (ASN.1)&quot;">14</a>].  ASN.1 is
   encoded using X.690 [<a href="#ref-16" title="&quot;Information technology ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)&quot;">16</a>].

   These formats are based on CMS (Cryptographic Message Syntax) defined
   in <a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>].  These electronic signatures are thus called CAdES,
   for "CMS Advanced Electronic Signatures".



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   Another document, TS 101 903 [<a href="#ref-TS101903" title="&quot;XML Advanced Electronic Signatures (XAdES)&quot;">TS101903</a>], describes formats for XML
   advanced electronic signatures (XAdES) built on XMLDSIG as specified
   in [<a href="#ref-XMLDSIG" title="&quot;XML-Signature Syntax and Processing&quot;">XMLDSIG</a>].

   In addition, the present document identifies other documents that
   define formats for Public Key Certificates, Attribute Certificates,
   and Certificate Revocation Lists and supporting protocols, including
   protocols for use by trusted third parties to support the operation
   of electronic signature creation and validation.

   Informative annexes include:

      - illustrations of extended forms of Electronic Signature formats
        that protect against various vulnerabilities and examples of
        validation processes (Annex B);

      - descriptions and explanations of some of the concepts used in
        the present document, giving a rationale for normative parts of
        the present document (Annex C);

      - information on protocols to interoperate with Trusted Service
        Providers (Annex D);

      - guidance on naming (Annex E);

      - an example structured content and MIME (Annex F);

      - the relationship between the present document and the directive
        on electronic signature and associated standardization
        initiatives (Annex G);

      - APIs to support the generation and verification of electronic
        signatures (Annex H);

      - cryptographic algorithms that may be used (Annex I); and

      - naming schemes (see Annex J).

<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>.  Definitions and Abbreviations</span>

<span class="h3"><a class="selflink" id="section-3.1" href="#section-3.1">3.1</a>.  Definitions</span>

   For the purposes of the present document, the following terms and
   definitions apply:

   Arbitrator: an arbitrator entity may be used to arbitrate a dispute
   between a signer and verifier when there is a disagreement on the
   validity of a digital signature.



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   Attribute Authority (AA): an authority that assigns privileges by
   issuing attribute certificates.

   Authority Certificate: a certificate issued to an authority (e.g.,
   either to a certification authority or an attribute authority).

   Attribute Authority Revocation List (AARL): a revocation list
   containing a list of references to certificates issued to AAs that
   are no longer considered valid by the issuing authority.

   Attribute Certificate Revocation List (ACRL): a revocation list
   containing a list of references to attribute certificates that are no
   longer considered valid by the issuing authority.

   Certification Authority Revocation List (CARL): a revocation list
   containing a list of public key certificates issued to certification
   authorities that are no longer considered valid by the certificate
   issuer.

   Certification Authority (CA): an authority trusted by one or more
   users to create and assign public key certificates; optionally, the
   certification authority may create the users' keys.

      NOTE: See ITU-T Recommendation X.509 [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>].

   Certificate Revocation List (CRL): a signed list indicating a set of
   public key certificates that are no longer considered valid by the
   certificate issuer.

   Digital Signature: data appended to, or a cryptographic
   transformation of, a data unit that allows a recipient of the data
   unit to prove the source and integrity of the data unit and protect
   against forgery, e.g., by the recipient.

      NOTE: See ISO 7498-2 [<a href="#ref-ISO7498-2" title="&quot;Information processing systems - Open Systems Interconnection - Basic Reference Model - Part 2: Security Architecture&quot;">ISO7498-2</a>].

   Electronic Signature: data in electronic form that is attached to or
   logically associated with other electronic data and that serves as a
   method of authentication.

      NOTE: See Directive 1999/93/EC of the European Parliament and of
      the Council of 13 December 1999 on a Community framework for
      electronic signatures [<a href="#ref-EUDirective">EUDirective</a>].

   Extended Electronic Signatures: electronic signatures enhanced by
   complementing the baseline requirements with additional data, such as
   time-stamp tokens and certificate revocation data, to address
   commonly recognized threats.



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   Explicit Policy-based Electronic Signature (EPES): an electronic
   signature where the signature policy that shall be used to validate
   it is explicitly specified.

   Grace Period: a time period that permits the certificate revocation
   information to propagate through the revocation process to relying
   parties.

   Initial Verification: a process performed by a verifier done after an
   electronic signature is generated in order to capture additional
   information that could make it valid for long-term verification.

   Public Key Certificate (PKC): public keys of a user, together with
   some other information, rendered unforgeable by encipherment with the
   private key of the certification authority that issued it.

      NOTE: See ITU-T Recommendation X.509 [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>].

   Rivest-Shamir-Adleman (RSA): an asymmetric cryptography algorithm
   based on the difficulty to factor very large numbers using a key
   pair: a private key and a public key.

   Signature Policy: a set of rules for the creation and validation of
   an electronic signature that defines the technical and procedural
   requirements for electronic signature creation and validation, in
   order to meet a particular business need, and under which the
   signature can be determined to be valid.

   Signature Policy Issuer: an entity that defines and issues a
   signature policy.

   Signature Validation Policy: part of the signature policy that
   specifies the technical requirements on the signer in creating a
   signature and verifier when validating a signature.

   Signer: an entity that creates an electronic signature.

   Subsequent Verification: a process performed by a verifier to assess
   the signature validity.

      NOTE: Subsequent verification may be done even years after the
      electronic signature was produced by the signer and completed by
      the initial verification, and it might not need to capture more
      data than those captured at the time of initial verification.

   Time-Stamp Token: a data object that binds a representation of a
   datum to a particular time, thus establishing evidence that the datum
   existed before that time.



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   Time-Mark: information in an audit trail from a Trusted Service
   Provider that binds a representation of a datum to a particular time,
   thus establishing evidence that the datum existed before that time.

   Time-Marking Authority: a trusted third party that creates records in
   an audit trail in order to indicate that a datum existed before a
   particular point in time.

   Time-Stamping Authority (TSA): a trusted third party that creates
   time-stamp tokens in order to indicate that a datum existed at a
   particular point in time.

   Time-Stamping Unit (TSU): a set of hardware and software that is
   managed as a unit and has a single time-stamp token signing key
   active at a time.

   Trusted Service Provider (TSP): an entity that helps to build trust
   relationships by making available or providing some information upon
   request.

   Validation Data: additional data that may be used by a verifier of
   electronic signatures to determine that the signature is valid.

   Valid Electronic Signature: an electronic signature that passes
   validation.

   Verifier: an entity that verifies evidence.

      NOTE 1: See ISO/IEC 13888-1 [<a href="#ref-ISO13888-1" title="&quot;IT security techniques - Non-repudiation - Part 1: General&quot;">ISO13888-1</a>].

      NOTE 2: Within the context of the present document, this is an
      entity that validates an electronic signature.

<span class="h3"><a class="selflink" id="section-3.2" href="#section-3.2">3.2</a>.  Abbreviations</span>

   For the purposes of the present document, the following abbreviations
   apply:

   AA           Attribute Authority
   AARL         Attribute Authority Revocation List
   ACRL         Attribute Certificate Revocation List
   API          Application Program Interface
   ASCII        American Standard Code for Information Interchange
   ASN.1        Abstract Syntax Notation 1
   CA           Certification Authority
   CAD          Card Accepting Device
   CAdES        CMS Advanced Electronic Signature
   CAdES-A      CAdES with Archive validation data



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   CAdES-BES    CAdES Basic Electronic Signature
   CAdES-C      CAdES with Complete validation data
   CAdES-EPES   CAdES Explicit Policy Electronic Signature
   CAdES-T      CAdES with Time
   CAdES-X      CAdES with eXtended validation data
   CAdES-X Long CAdES with EXtended Long validation data
   CARL         Certification Authority Revocation List
   CMS          Cryptographic Message Syntax
   CRL          Certificate Revocation List
   CWA          CEN (European Committee for Standardization) Workshop
                Agreement
   DER          Distinguished Encoding Rules (for ASN.1)
   DSA          Digital Signature Algorithm
   EDIFACT      Electronic Data Interchange For Administration,
                Commerce and Transport
   EESSI        European Electronic Signature Standardization
                Initiative
   EPES         Explicit Policy-based Electronic Signature
   ES           Electronic Signature
   ESS          Enhanced Security Services (enhances CMS)
   IDL          Interface Definition Language
   MIME         Multipurpose Internet Mail Extensions
   OCSP         Online Certificate Status Provider
   OID          Object IDentifier
   PKC          Public Key Certificate
   PKIX         Public Key Infrastructure using X.509
                (IETF Working Group)
   RSA          Rivest-Shamir-Adleman
   SHA-1        Secure Hash Algorithm 1
   TSA          Time-Stamping Authority
   TSP          Trusted Service Provider
   TST          Time-Stamp Token
   TSU          Time-Stamping Unit
   URI          Uniform Resource Identifier
   URL          Uniform Resource Locator
   XML          Extensible Markup Language
   XMLDSIG      XML Digital Signature

<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>.  Overview</span>

   The present document defines a number of Electronic Signature (ES)
   formats that build on CMS (<a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]) by adding signed and
   unsigned attributes.

   This section:

      - provides an introduction to the major parties involved
        (<a href="#section-4.1">Section 4.1</a>),



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      - introduces the concept of signature policies (<a href="#section-4.2">Section 4.2</a>),

      - provides an overview of the various ES formats (<a href="#section-4.3">Section 4.3</a>),

      - introduces the concept of validation data, and provides an
        overview of formats that incorporate validation data
        (<a href="#section-4.4">Section 4.4</a>), and

      - presents relevant considerations on arbitration
        (<a href="#section-4.5">Section 4.5</a>) and for the validation process (<a href="#section-4.6">Section 4.6</a>).

   The formal specifications of the attributes are specified in Sections
   5 and 6; Annexes C and D provide rationale for the definitions of the
   different ES forms.

<span class="h3"><a class="selflink" id="section-4.1" href="#section-4.1">4.1</a>.  Major Parties</span>

   The major parties involved in a business transaction supported by
   electronic signatures, as defined in the present document, are:

      - the signer;
      - the verifier;
      - Trusted Service Providers (TSP); and
      - the arbitrator.

   The signer is the entity that creates the electronic signature.  When
   the signer digitally signs over data using the prescribed format,
   this represents a commitment on behalf of the signing entity to the
   data being signed.

   The verifier is the entity that validates the electronic signature;
   it may be a single entity or multiple entities.

   The Trusted Service Providers (TSPs) are one or more entities that
   help to build trust relationships between the signer and verifier.
   They support the signer and verifier by means of supporting services
   including: user certificates, cross-certificates, time-stamp tokens,
   CRLs, ARLs, and OCSP responses.  The following TSPs are used to
   support the functions defined in the present document:

      - Certification Authorities;
      - Registration Authorities;
      - CRL Issuers;
      - OCSP Responders;
      - Repository Authorities (e.g., a Directory);
      - Time-Stamping Authorities;
      - Time-Marking Authorities; and
      - Signature Policy Issuers.



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   Certification Authorities provide users with public key certificates
   and a revocation service.

   Registration Authorities allow the identification and registration of
   entities before a CA generates certificates.

   Repository Authorities publish CRLs issued by CAs, signature policies
   issued by Signature Policy Issuers, and optionally public key
   certificates.

   Time-Stamping Authorities attest that some data was formed before a
   given trusted time.

   Time-Marking Authorities record that some data was formed before a
   given trusted time.

   Signature Policy Issuers define the signature policies to be used by
   signers and verifiers.

   In some cases, the following additional TSPs are needed:

      - Attribute Authorities.

   Attributes Authorities provide users with attributes linked to public
   key certificates.

   An Arbitrator is an entity that arbitrates in disputes between a
   signer and a verifier.

<span class="h3"><a class="selflink" id="section-4.2" href="#section-4.2">4.2</a>.  Signature Policies</span>

   The present document includes the concept of signature policies that
   can be used to establish technical consistency when validating
   electronic signatures.

   When a comprehensive signature policy used by the verifier is either
   explicitly indicated by the signer or implied by the data being
   signed, then a consistent result can be obtained when validating an
   electronic signature.

   When the signature policy being used by the verifier is neither
   indicated by the signer nor can be derived from other data, or the
   signature policy is incomplete, then verifiers, including
   arbitrators, may obtain different results when validating an
   electronic signature.  Therefore, comprehensive signature policies
   that ensure consistency of signature validation are recommended from
   both the signer's and verifier's point of view.




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   Further information on signature policies is provided in:

      - TR 102 038 [<a href="#ref-TR102038" title="&quot;Electronic Signatures and Infrastructures (ESI); XML format for signature policies&quot;">TR102038</a>];
      - Sections <a href="#section-5.8.1">5.8.1</a>, C.1, and C.3.1 of the present document;
      - <a href="./rfc3125">RFC 3125</a> [<a href="./rfc3125" title="&quot;Electronic Signature Policies&quot;">RFC3125</a>]; and
      - TR 102 272 [<a href="#ref-TR102272" title="&quot;Electronic Signatures and Infrastructures (ESI); ASN.1 format for signature policies&quot;">TR102272</a>].

<span class="h3"><a class="selflink" id="section-4.3" href="#section-4.3">4.3</a>.  Electronic Signature Formats</span>

   The current section provides an overview for two forms of CMS
   advanced electronic signature specified in the present document,
   namely, the CAdES Basic Electronic Signature (CAdES-BES) and the
   CAdES Explicit Policy-based Electronic Signature (CAdES-EPES).
   Conformance to the present document mandates that the signer create
   one of these formats.

<span class="h4"><a class="selflink" id="section-4.3.1" href="#section-4.3.1">4.3.1</a>.  CAdES Basic Electronic Signature (CAdES-BES)</span>

   A CAdES Basic Electronic Signature (CAdES-BES), in accordance with
   the present document, contains:

      - The signed user data (e.g., the signer's document), as defined
        in CMS (<a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]);

      - A collection of mandatory signed attributes, as defined in CMS
        (<a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]) and in ESS (<a href="./rfc2634">RFC 2634</a> [<a href="#ref-5" title="&quot;Enhanced Security Services for S/MIME&quot;">5</a>]);

      - Additional mandatory signed attributes, defined in the present
        document; and

      - The digital signature value computed on the user data and, when
        present, on the signed attributes, as defined in CMS (<a href="./rfc3852">RFC 3852</a>
        [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]).

   A CAdES Basic Electronic Signature (CAdES-BES), in accordance with
   the present document, may contain:

      - a collection of additional signed attributes; and

      - a collection of optional unsigned attributes.

   The mandatory signed attributes are:

      - Content-type.  It is defined in <a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>] and specifies the
        type of the EncapsulatedContentInfo value being signed.  Details
        are provided in <a href="#section-5.7.1">Section 5.7.1</a> of the present document.
        Rationale for its inclusion is provided in Annex C.3.7;




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      - Message-digest.  It is defined in <a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>] and specifies the
        message digest of the eContent OCTET STRING within
        encapContentInfo being signed.  Details are provided in <a href="#section-5.7.2">Section</a>
        <a href="#section-5.7.2">5.7.2</a>;

      - ESS signing-certificate OR ESS signing-certificate-v2.  The ESS
        signing-certificate attribute is defined in Enhanced Security
        Services (ESS), <a href="./rfc2634">RFC 2634</a> [<a href="#ref-5" title="&quot;Enhanced Security Services for S/MIME&quot;">5</a>], and only allows for the use of
        SHA-1 as a digest algorithm.  The ESS signing-certificate-v2
        attribute is defined in "ESS Update: Adding CertID Algorithm
        Agility", <a href="./rfc5035">RFC 5035</a> [<a href="#ref-15" title="&quot;Enhanced Security Services (ESS) Update: Adding CertID Algorithm Agility&quot;">15</a>], and allows for the use of any digest
        algorithm.  A CAdES-BES claiming compliance with the present
        document must include one of them.  <a href="#section-5.7.3">Section 5.7.3</a> provides the
        details of these attributes.  Rationale for its inclusion is
        provided in Annex C.3.3.

   Optional signed attributes may be added to the CAdES-BES, including
   optional signed attributes defined in CMS (<a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]), ESS (<a href="./rfc2634">RFC</a>
   <a href="./rfc2634">2634</a> [<a href="#ref-5" title="&quot;Enhanced Security Services for S/MIME&quot;">5</a>]), and the present document.  Listed below are optional
   attributes that are defined in <a href="#section-5">Section 5</a> and have a rationale
   provided in Annex C:

      - Signing-time: as defined in CMS (<a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]), indicates the
        time of the signature, as claimed by the signer.  Details and
        short rationale are provided in <a href="#section-5.9.1">Section 5.9.1</a>.  Annex C.3.6
        provides the rationale.

      - content-hints: as defined in ESS (<a href="./rfc2634">RFC 2634</a> [<a href="#ref-5" title="&quot;Enhanced Security Services for S/MIME&quot;">5</a>]), provides
        information that describes the innermost signed content of a
        multi-layer message where one content is encapsulated in
        another.  <a href="#section-5.10.1">Section 5.10.1</a> provides the specification details.
        Annex C.3.8 provides the rationale.

      - content-reference: as defined in ESS (<a href="./rfc2634">RFC 2634</a> [<a href="#ref-5" title="&quot;Enhanced Security Services for S/MIME&quot;">5</a>]), can be
        incorporated as a way to link request and reply messages in an
        exchange between two parties.  <a href="#section-5.10.1">Section 5.10.1</a> provides the
        specification details.  Annex C.3.9 provides the rationale.

      - content-identifier: as defined in ESS (<a href="./rfc2634">RFC 2634</a> [<a href="#ref-5" title="&quot;Enhanced Security Services for S/MIME&quot;">5</a>]), contains
        an identifier that may be used later on in the previous
        content-reference attribute.  <a href="#section-5.10.2">Section 5.10.2</a> provides the
        specification details.

      - commitment-type-indication: this attribute is defined by the
        present document as a way to indicate the commitment endorsed by
        the signer when producing the signature.  <a href="#section-5.11.1">Section 5.11.1</a>
        provides the specification details.  Annex C.3.2 provides the
        rationale.



<span class="grey">Pinkas, et al.               Informational                     [Page 16]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-17" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


      - signer-location: this attribute is defined by the present
        document.  It allows the signer to indicate the place where the
        signer purportedly produced the signature.  <a href="#section-5.11.2">Section 5.11.2</a>
        provides the specification details.  Annex C.3.5 provides the
        rationale.

      - signer-attributes: this attribute is defined by the present
        document.  It allows a claimed or certified role to be
        incorporated into the signed information.  <a href="#section-5.11.3">Section 5.11.3</a>
        provides the specification details.  Annex C.3.4 provides the
        rationale.

      - content-time-stamp: this attribute is defined by the present
        document.  It allows a time-stamp token of the data to be signed
        to be incorporated into the signed information.  It provides
        proof of the existence of the data before the signature was
        created.  <a href="#section-5.11.4">Section 5.11.4</a> provides the specification details.
        Annex C.3.6 provides the rationale.

   A CAdES-BES form can also incorporate instances of unsigned
   attributes, as defined in CMS (<a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]) and ESS (<a href="./rfc2634">RFC 2634</a> [<a href="#ref-5" title="&quot;Enhanced Security Services for S/MIME&quot;">5</a>]).

      - CounterSignature, as defined in CMS (<a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]); it can be
        incorporated wherever embedded signatures (i.e., a signature on
        a previous signature) are needed.  <a href="#section-5.9.2">Section 5.9.2</a> provides the
        specification details.  Annex C.5 in Annex C provides the
        rationale.

   The structure of the CAdES-BES is illustrated in Figure 1.

                +------Elect.Signature (CAdES-BES)------+
                |+----------------------------------- + |
                ||+---------+ +----------+            | |
                |||Signer's | |  Signed  |  Digital   | |
                |||Document | |Attributes| Signature  | |
                |||         | |          |            | |
                ||+---------+ +----------+            | |
                |+------------------------------------+ |
                +---------------------------------------+

                  Figure 1: Illustration of a CAdES-BES

   The signer's conformance requirements of a CAdES-BES are defined in
   <a href="#section-8.1">Section 8.1</a>.







<span class="grey">Pinkas, et al.               Informational                     [Page 17]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-18" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


      NOTE: The CAdES-BES is the minimum format for an electronic
      signature to be generated by the signer.  On its own, it does not
      provide enough information for it to be verified in the longer
      term.  For example, revocation information issued by the relevant
      certificate status information issuer needs to be available for
      long-term validation (see <a href="#section-4.4.2">Section 4.4.2</a>).

   The CAdES-BES satisfies the legal requirements for electronic
   signatures, as defined in the European Directive on Electronic
   Signatures, (see Annex C for further discussion on the relationship
   of the present document to the Directive).  It provides basic
   authentication and integrity protection.

   The semantics of the signed data of a CAdES-BES or its context may
   implicitly indicate a signature policy to the verifier.

   Specification of the contents of signature policies is outside the
   scope of the present document.  However, further information on
   signature policies is provided in TR 102 038 [<a href="#ref-TR102038" title="&quot;Electronic Signatures and Infrastructures (ESI); XML format for signature policies&quot;">TR102038</a>], <a href="./rfc3125">RFC 3125</a>
   [<a href="./rfc3125" title="&quot;Electronic Signature Policies&quot;">RFC3125</a>], and Sections <a href="#section-5.8.1">5.8.1</a>, C.1, and C.3.1 of the present
   document.

<span class="h4"><a class="selflink" id="section-4.3.2" href="#section-4.3.2">4.3.2</a>.  CAdES Explicit Policy-based Electronic Signatures (CAdES-EPES)</span>

   A CAdES Explicit Policy-based Electronic Signature (CAdES-EPES), in
   accordance with the present document, extends the definition of an
   electronic signature to conform to the identified signature policy.

   A CAdES Explicit Policy-based Electronic Signature (CAdES-EPES)
   incorporates a signed attribute (sigPolicyID attribute) indicating
   the signature policy that shall be used to validate the electronic
   signature.  This signed attribute is protected by the signature.  The
   signature may also have other signed attributes required to conform
   to the mandated signature policy.

   <a href="#section-5.7.3">Section 5.7.3</a> provides the details on the specification of
   signature-policy-identifier attribute.  Annex C.1 provides a short
   rationale.  Specification of the contents of signature policies is
   outside the scope of the present document.

   Further information on signature policies is provided in TR 102 038
   [<a href="#ref-TR102038" title="&quot;Electronic Signatures and Infrastructures (ESI); XML format for signature policies&quot;">TR102038</a>] and Sections <a href="#section-5.8.1">5.8.1</a>, C.1, and C.3.1 of the present
   document.








<span class="grey">Pinkas, et al.               Informational                     [Page 18]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-19" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


   The structure of the CAdES-EPES is illustrated in Figure 2.

          +------------- Elect.Signature (CAdES-EPES) ---------------+
          |                                                          |
          |+-------------------------------------------------------+ |
          || +-----------+                                         | |
          || |           |   +---------------------------+         | |
          || |           |   |   +----------+            |         | |
          || | Signer's  |   |   |Signature | Signed     | Digital | |
          || | Document  |   |   |Policy ID | Attributes |Signature| |
          || |           |   |   +----------+            |         | |
          || |           |   +---------------------------+         | |
          || +-----------+                                         | |
          |+-------------------------------------------------------+ |
          |                                                          |
          +----------------------------------------------------------+

                   Figure 2: Illustration of a CAdES-EPES

   The signer's conformance requirements of CAdES-EPES are defined in
   <a href="#section-8.2">Section 8.2</a>.

<span class="h3"><a class="selflink" id="section-4.4" href="#section-4.4">4.4</a>.  Electronic Signature Formats with Validation Data</span>

   Validation of an electronic signature, in accordance with the present
   document, requires additional data needed to validate the electronic
   signature.  This additional data is called validation data, and
   includes:

      - Public Key Certificates (PKCs);

      - revocation status information for each PKC;

      - trusted time-stamps applied to the digital signature, otherwise
        a time-mark shall be available in an audit log.

      - when appropriate, the details of a signature policy to be used
        to verify the electronic signature.

   The validation data may be collected by the signer and/or the
   verifier.  When the signature-policy-identifier signed attribute is
   present, it shall meet the requirements of the signature policy.









<span class="grey">Pinkas, et al.               Informational                     [Page 19]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-20" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


   Validation data includes CA certificates as well as revocation status
   information in the form of Certificate Revocation Lists (CRLs) or
   certificate status information (OCSP) provided by an online service.
   Validation data also includes evidence that the signature was created
   before a particular point in time; this may be either a time-stamp
   token or time-mark.

   The present document defines unsigned attributes able to contain
   validation data that can be added to CAdES-BES and CAdES-EPES,
   leading to electronic signature formats that include validation data.
   The sections below summarize these formats and their most relevant
   characteristics.

<span class="h4"><a class="selflink" id="section-4.4.1" href="#section-4.4.1">4.4.1</a>.  Electronic Signature with Time (CAdES-T)</span>

   An electronic signature with time (CAdES-T), in accordance with the
   present document, is when there exits trusted time associated with
   the ES.

   The trusted time may be provided by:

      - a time-stamp attribute as an unsigned attribute added to the ES;
        and

      - a time-mark of the ES provided by a Trusted Service Provider.

   The time-stamp attribute contains a time-stamp token of the
   electronic signature value.  <a href="#section-6.1.1">Section 6.1.1</a> provides the specification
   details.  Annex C.4.3 provides the rationale.

   A time-mark provided by a Trusted Service would have a similar effect
   to the signature-time-stamp attribute, but in this case, no attribute
   is added to the ES, as it is the responsibility of the TSP to provide
   evidence of a time-mark when required to do so.  The management of
   time marks is outside the scope of the present document.

   Trusted time provides the initial steps towards providing long-term
   validity.  Electronic signatures with the time-stamp attribute or a
   time-marked BES/EPES, forming the CAdES-T are illustrated in Figure
   3.











<span class="grey">Pinkas, et al.               Informational                     [Page 20]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-21" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


   +-------------------------------------------------CAdES-T ---------+
   |+------ CAdES-BES or CAdES-EPES -------+                          |
   ||+-----------------------------------+ | +----------------------+ |
   |||+---------+ +----------+           | | |                      | |
   ||||Signer's | |  Signed  |  Digital  | | | Signature-time-stamp | |
   ||||Document | |Attributes| Signature | | | attribute required   | |
   ||||         | |          |           | | | when using time      | |
   |||+---------+ +----------+           | | | stamps.              | |
   ||+-----------------------------------+ | |                      | |
   |+--------------------------------------+ | or the BES/EPES      | |
   |                                         | shall be time-marked | |
   |                                         |                      | |
   |                                         | Management and       | |
   |                                         | provision of time    | |
   |                                         | mark is the          | |
   |                                         | responsibility of    | |
   |                                         | the TSP.             | |
   |                                         +----------------------+ |
   +------------------------------------------------------------------+

                Figure 3: Illustration of CAdES-T formats

      NOTE 1: A time-stamp token is added to the CAdES-BES or CAdES-EPES
      as an unsigned attribute.

      NOTE 2: Time-stamp tokens that may themselves include unsigned
      attributes required to validate the time-stamp token, such as the
      complete-certificate-references and complete-revocation-references
      attributes, as defined by the present document.

<span class="h4"><a class="selflink" id="section-4.4.2" href="#section-4.4.2">4.4.2</a>.  ES with Complete Validation Data References (CAdES-C)</span>

   Electronic Signature with Complete validation data references
   (CAdES-C), in accordance with the present document, adds to the
   CAdES-T the complete-certificate-references and
   complete-revocation-references attributes, as defined by the present
   document.  The complete-certificate-references attribute contains
   references to all the certificates present in the certification path
   used for verifying the signature.  The complete-revocation-references
   attribute contains references to the CRLs and/or OCSPs responses used
   for verifying the signature.  <a href="#section-6.2">Section 6.2</a> provides the specification
   details.  Storing the references allows the values of the
   certification path and the CRLs or OCSPs responses to be stored
   elsewhere, reducing the size of a stored electronic signature format.







<span class="grey">Pinkas, et al.               Informational                     [Page 21]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-22" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


   Sections C.4.1 to C.4.2 provide rationale on the usage of validation
   data and when it is suitable to generate the CAdES-C form.
   Electronic signatures, with the additional validation data forming
   the CAdES-C, are illustrated in Figure 4.

   +------------------------- CAdES-C --------------------------------+
   |+----------------------------- CAdES-T ---------+                 |
   ||                                  +----------+ | +-------------+ |
   ||                                  |Timestamp | | |             | |
   ||                                  |attribute | | |             | |
   ||+- CAdES-BES or CAdES-EPES ------+|over      | | |             | |
   |||                                ||digital   | | | Complete    | |
   |||+---------++----------+         ||signature | | | certificate | |
   ||||Signer's ||  Signed  | Digital ||is        | | |     and     | |
   ||||Document ||Attributes|Signature||mandatory | | | revocation  | |
   ||||         ||          |         ||if is not | | | references  | |
   |||+---------++----------+         ||timemarked| | |             | |
   ||+--------------------------------++----------+ | |             | |
   |+-----------------------------------------------+ +-------------+ |
   +------------------------------------------------------------------+

             Figure 4: Illustration of CAdES-C format

      NOTE 1: The complete certificate and revocation references are
      added to the CAdES-T as an unsigned attribute.

      NOTE 2: As a minimum, the signer will provide the CAdES-BES or,
      when indicating that the signature conforms to an explicit signing
      policy, the CAdES-EPES.

      NOTE 3: To reduce the risk of repudiating signature creation, the
      trusted time indication needs to be as close as possible to the
      time the signature was created.  The signer or a TSP could provide
      the CAdES-T; if not, the verifier should create the CAdES-T on
      first receipt of an electronic signature because the CAdES-T
      provides independent evidence of the existence of the signature
      prior to the trusted time indication.

      NOTE 4: A CAdES-T trusted time indication must be created before a
      certificate has been revoked or expired.

      NOTE 5: The signer and TSP could provide the CAdES-C to minimize
      this risk, and when the signer does not provide the CAdES-C, the
      verifier should create the CAdES-C when the required component of
      revocation and validation data become available; this may require
      a grace period.





<span class="grey">Pinkas, et al.               Informational                     [Page 22]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-23" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


      NOTE 6: A grace period permits certificate revocation information
      to propagate through the revocation processes.  This period could
      extend from the time an authorized entity requests certificate
      revocation to when the information is available for the relying
      party to use.  In order to make sure that the certificate was not
      revoked at the time the signature was time-marked or time-stamped,
      verifiers should wait until the end of the grace period.  A
      signature policy may define specific values for grace periods.

   An illustration of a grace period is provided in Figure 5.

               +&lt;--------------Grace Period ---------&gt;+
   ----+-------+-------+--------+---------------------+----------+
       ^       ^       ^        ^                     ^          ^
       |       |       |        |                     |          |
       |       |       |        |                     |          |
   Signature   |     First      |                   Second       |
    creation   |   revocation   |                  revocation    |
     time      |     status     |                    status      |
               |    checking    |                  checking      |
               |                |                                |
           Time-stamp      Certification                       Build
              or              path                            CAdES-C
           time-mark      construction
             over          &amp; verification
           signature

               Figure 5: Illustration of a grace period

      NOTE 7: CWA 14171 [<a href="#ref-CWA14171" title="&quot;General Guidelines for Electronic Signature Verification&quot;">CWA14171</a>] specifies a signature validation
      process using CAdES-T, CAdES-C, and a grace period.  Annex B
      provides example validation processes.  Annex C.4 provides
      additional information about applying grace periods during the
      validation process.

   The verifier's conformance requirements are defined in <a href="#section-8.3">Section 8.3</a>
   for time-stamped CAdES-C, and <a href="#section-8.4">Section 8.4</a> for time-marked CAdES-C.
   The present document only defines conformance requirements for the
   verifier up to an ES with Complete validation data (CAdES-C).  This
   means that none of the extended and archive forms of electronic
   signatures, as defined in Sections <a href="#section-4.4.3">4.4.3</a> to <a href="#section-4.4.4">4.4.4</a>, need to be
   implemented to achieve conformance to the present document.

<span class="h4"><a class="selflink" id="section-4.4.3" href="#section-4.4.3">4.4.3</a>.  Extended Electronic Signature Formats</span>

   CAdES-C can be extended by adding unsigned attributes to the
   electronic signature.  The present document defines various unsigned
   attributes that are applicable for very long-term verification, and



<span class="grey">Pinkas, et al.               Informational                     [Page 23]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-24" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


   for preventing some disaster situations that are discussed in Annex
   C.  Annex B provides the details of the various extended formats, all
   the required unsigned attributes for each type, and how they can be
   used within the electronic signature validation process.  The
   sections below give an overview of the various forms of extended
   signature formats in the present document.

<span class="h5"><a class="selflink" id="section-4.4.3.1" href="#section-4.4.3.1">4.4.3.1</a>.  EXtended Long Electronic Signature (CAdES-X Long)</span>

   Extended Long format (CAdES-X Long), in accordance with the present
   document, adds the certificate-values and revocation-values
   attributes to the CAdES-C format.  The first one contains the whole
   certificate path required for verifying the signature; the second one
   contains the CRLs and/OCSP responses required for the validation of
   the signature.  This provides a known repository of certificate and
   revocation information required to validate a CAdES-C and prevents
   such information from getting lost.  Sections <a href="#section-6.3.3">6.3.3</a> and <a href="#section-6.3.4">6.3.4</a> give
   specification details.  Annex B.1.1 gives details on the production
   of the format.  Annexes C4.1 to C.4.2 provide the rationale.

   The structure of the CAdES-X Long format is illustrated in Figure 6.

   +----------------------- CAdES-X-Long -----------------------------+
   |+------------------------------------ CadES-C --+                 |
   ||                                  +----------+ | +-------------+ |
   ||+------ CAdES -------------------+|Timestamp | | |             | |
   |||                                ||  over    | | | Complete    | |
   |||+---------++----------+         ||digital   | | | certificate | |
   ||||Signer's ||  Signed  | Digital ||signature | | |     and     | |
   ||||Document ||Attributes|Signature||          | | | revocation  | |
   ||||         ||          |         ||Optional  | | |    data     | |
   |||+---------++----------+         ||when      | | |             | |
   ||+--------------------------------+|timemarked| | |             | |
   ||                                  +----------+ | |             | |
   ||                               +-------------+ | +-------------+ |
   ||                               | Complete    | |                 |
   ||                               | certificate | |                 |
   ||                               | and         | |                 |
   ||                               | revocation  | |                 |
   ||                               | references  | |                 |
   ||                               +-------------+ |                 |
   |+-----------------------------------------------+                 |
   |                                                                  |
   +------------------------------------------------------------------+

                  Figure 6: Illustration of CAdES-X-Long





<span class="grey">Pinkas, et al.               Informational                     [Page 24]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-25" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


<span class="h5"><a class="selflink" id="section-4.4.3.2" href="#section-4.4.3.2">4.4.3.2</a>.  EXtended Electronic Signature with Time Type 1</span>
          (CAdES-X Type 1)

   Extended format with time type 1 (CAdES-X Type 1), in accordance with
   the present document, adds the CAdES-C-time-stamp attribute, whose
   content is a time-stamp token on the CAdES-C itself, to the CAdES-C
   format.

   This provides an integrity and trusted time protection over all the
   elements and references.  It may protect the certificates, CRLs, and
   OCSP responses in case of a later compromise of a CA key, CRL key, or
   OCSP issuer key.  <a href="#section-6.3.5">Section 6.3.5</a> provides the specification details.

   Annex B.1.2 gives details on the production of the time-stamping
   process.  Annex C.4.4.1 provides the rationale.

   The structure of the CAdES-X Type 1 format is illustrated in Figure
   7.

  +----------------------- CAdES-X-Type 1 ------------------------------+
  |+-------------------------------------- CAdES-C -----+               |
  ||                                    +-------------+ | +-----------+ |
  ||+--------- CAdES ------------------+| Timestamp   | | |           | |
  |||                                  || over        | | |           | |
  |||+---------++----------+           || digital     | | |           | |
  ||||Signer's ||  Signed  |  Digital  || signature   | | | Timestamp | |
  ||||Document ||Attributes| Signature ||             | | |   over    | |
  ||||         ||          |           || Optional    | | | CAdES-C   | |
  |||+---------++----------+           || when        | | |           | |
  ||+----------------------------------+| time-marked | | |           | |
  ||                                    +-------------+ | |           | |
  ||                                    +-------------+ | +-----------+ |
  ||                                    | Complete    | |               |
  ||                                    | certificate | |               |
  ||                                    | and         | |               |
  ||                                    | revocation  | |               |
  ||                                    | references  | |               |
  ||                                    +-------------+ |               |
  |+----------------------------------------------------+               |
  +---------------------------------------------------------------------+

                  Figure 7: Illustration of CAdES-X Type  1









<span class="grey">Pinkas, et al.               Informational                     [Page 25]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-26" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


<span class="h5"><a class="selflink" id="section-4.4.3.3" href="#section-4.4.3.3">4.4.3.3</a>.  EXtended Electronic Signature with Time Type 2</span>
          (CAdES-X Type 2)

   Extended format with time type 2 (CAdES-X Type 2), in accordance with
   the present document, adds to the CAdES-C format the
   CAdES-C-time-stamped-certs-crls-references attribute, whose content
   is a time-stamp token on the certification path and revocation
   information references.  This provides an integrity and trusted time
   protection over all the references.

   It may protect the certificates, CRLs and OCSP responses in case of a
   later compromise of a CA key, CRL key or OCSP issuer key.

   Both CAdES-X Type 1 and CAdES-X Type 2 counter the same threats, and
   the usage of one or the other depends on the environment.  <a href="#section-6.3.5">Section</a>
   <a href="#section-6.3.5">6.3.5</a> provides the specification details.  Annex B.1.3 gives details
   on the production of the time-stamping process.  Annex C.4.4.2
   provides the rationale.

   The structure of the CAdES-X Type 2 format is illustrated in Figure
   8.

+------------------------- CAdES-X-Type 2 ----------------------------+
|+----------------------------------------CAdES-C ---+                |
||                                     +------------+|                |
||+----- CAdES -----------------------+| Timestamp  ||                |
|||                                   || over       ||                |
|||+---------+ +----------+           || digital    || +-------------+|
||||Signer's | |  Signed  |  Digital  || signature  || | Time-stamp  ||
||||Document | |Attributes| signature ||            || | only over   ||
||||         | |          |           || optional   || | complete    ||
|||+---------+ +----------+           || when       || | certificate ||
||+-----------------------------------+| timemarked || |    and      ||
||                                     +------------+| | revocation  ||
||                                   +-------------+ | | references  ||
||                                   | Complete    | | +-------------+|
||                                   | certificate | |                |
||                                   | and         | |                |
||                                   | revocation  | |                |
||                                   | references  | |                |
||                                   +-------------+ |                |
|+---------------------------------------------------+                |
+---------------------------------------------------------------------+

                  Figure 8: Illustration of CAdES-X Type 2






<span class="grey">Pinkas, et al.               Informational                     [Page 26]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-27" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


<span class="h5"><a class="selflink" id="section-4.4.3.4" href="#section-4.4.3.4">4.4.3.4</a>.  EXtended Long Electronic Signature with Time (CAdES-X Long</span>
<span class="h5">          Type 1 or 2)</span>

   Extended Long with Time (CAdES-X Long Type 1 or 2), in accordance
   with the present document, is a combination of CAdES-X Long and one
   of the two former types (CAdES-X Type 1 and CAdES-X Type 2).  Annex
   B.1.4 gives details on the production of the time-stamping process.
   Annex C.4.8 in Annex C provides the rationale.

   The structure of the CAdES-X Long Type 1 and CAdES-X Long Type 2
   format is illustrated in Figure 9.

   +------------------ CAdES-X Long Type 1 or 2 -----------------------+
   |                                                   +--------------+|
   |+-------------------------------------- CAdES-C --+|+------------+||
   ||                                                 ||| Timestamp  |||
   ||+------- CAdES --------------------++----------+ |||   over     |||
   |||                                  ||Timestamp | |||  CAdES-C   |||
   |||                                  ||over      | ||+------------+||
   |||+---------++----------+           ||digital   | ||      OR      ||
   ||||Signer's ||  Signed  | Digital   ||signature | ||+------------+||
   ||||Document ||Attributes| signature ||          | ||| Timestamp  |||
   ||||         ||          |           ||Optional  | ||| only over  |||
   |||+---------++----------+           ||when      | ||| complete   |||
   ||+----------------------------------+|timemarked| ||| certificate|||
   ||                                    +----------+ |||    and     |||
   ||                                                 ||| Revocation |||
   ||                                 +-------------+ ||| References |||
   ||                                 | Complete    | ||+------------+||
   ||                                 | certificate | |+--------------+|
   ||                                 | and         | | +------------+ |
   ||                                 | revocation  | | | Complete   | |
   ||                                 | references  | | |certificate | |
   ||                                 +-------------+ | |   and      | |
   |+-------------------------------------------------+ |revocation  | |
   |                                                    |  value     | |
   |                                                    +------------+ |
   +-------------------------------------------------------------------+

     Figure 9: Illustration of CAdES-X Long Type 1 and CAdES Long Type 2

<span class="h4"><a class="selflink" id="section-4.4.4" href="#section-4.4.4">4.4.4</a>.  Archival Electronic Signature (CAdES-A)</span>

   Archival Form (CAdES-A), in accordance with the present document,
   builds on a CAdES-X Long or a CAdES-X Long Type 1 or 2 by adding one
   or more archive-time-stamp attributes.  This form is used for
   archival of long-term signatures.  Successive time-stamps protect the
   whole material against vulnerable hashing algorithms or the breaking



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   of the cryptographic material or algorithms.  <a href="#section-6.4">Section 6.4</a> contains
   the specification details.  Sections C.4.5 and C.4.8 provide the
   rationale.

   The structure of the CAdES-A form is illustrated in Figure 10.

  +---------------------------CAdES-A ---------------------------------+
  |+----------------------------------------------------+              |
  ||                                    +--------------+| +----------+ |
  ||+----------------------CAdES-C ----+|+------------+|| |          | |
  |||                     +----------+ ||| Timestamp  ||| |          | |
  |||+---- CAdES-BES ----+|Timestamp | |||    over    ||| |          | |
  ||||    or CAdeS-EPES  ||  over    | |||   CAdES-C  ||| |  Archive | |
  ||||                   ||digital   | ||+------------+|| |          | |
  ||||                   ||signature | ||      or      || |Timestamp | |
  ||||                   ||          | ||+------------+|| |          | |
  ||||                   ||Optional  | ||| Timestamp  ||| |          | |
  ||||                   ||when      | ||| only over  ||| |          | |
  ||||                   ||Timemarked| ||| complete   ||| |          | |
  |||+-------------------+|          | ||| certificate||| +----------+ |
  |||                     +----------+ |||    and     |||              |
  |||                  +-------------+ ||| revocation |||              |
  |||                  | Complete    | ||| references |||              |
  |||                  | certificate | ||+------------+||              |
  |||                  | and         | |+--------------+|              |
  |||                  | revocation  | | +------------+ |              |
  |||                  | references  | | |  Complete  | |              |
  |||                  +-------------+ | |certificate | |              |
  |||                                  | |    and     | |              |
  ||+----------------------------------+ |revocation  | |              |
  ||                                     |  values    | |              |
  ||                                     +------------+ |              |
  |+----------------------------------------------------+              |
  +--------------------------------------------------------------------+

                     Figure 10: Illustration of CAdES-A

<span class="h3"><a class="selflink" id="section-4.5" href="#section-4.5">4.5</a>.  Arbitration</span>

   The CAdES-C may be used for arbitration should there be a dispute
   between the signer and verifier, provided that:

      - the arbitrator knows where to retrieve the signer's certificate
        (if not already present), all the cross-certificates and the
        required CRLs, ACRLs, or OCSP responses referenced in the
        CAdES-C;





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      - when time-stamping in the CAdES-T is being used, the certificate
        from the TSU that has issued the time-stamp token in the CAdES-T
        format is still within its validity period;

      - when time-stamping in the CAdES-T is being used, the certificate
        from the TSU that has issued the time-stamp token in the CAdES-T
        format is not revoked at the time of arbitration;

      - when time-marking in the CAdES-T is being used, a reliable audit
        trail from the Time-Marking Authority is available for
        examination regarding the time;

      - none of the private keys corresponding to the certificates used
        to verify the signature chain have ever been compromised;

      - the cryptography used at the time the CAdES-C was built has not
        been broken at the time the arbitration is performed; and

      - if the signature policy can be explicitly or implicitly
        identified, then an arbitrator is able to determine the rules
        required to validate the electronic signature.

<span class="h3"><a class="selflink" id="section-4.6" href="#section-4.6">4.6</a>.  Validation Process</span>

   The validation process validates an electronic signature; the output
   status of the validation process can be:

      - invalid;

      - incomplete validation; or

      - valid.

   An invalid response indicates that either the signature format is
   incorrect or that the digital signature value fails verification
   (e.g., the integrity check on the digital signature value fails, or
   any of the certificates on which the digital signature verification
   depends is known to be invalid or revoked).

   An incomplete validation response indicates that the signature
   validation status is currently unknown.  In the case of incomplete
   validation, additional information may be made available to the
   application or user, thus allowing them to decide what to do with the
   electronic signature.  In the case of incomplete validation, the
   electronic signature may be checked again at some later time when
   additional information becomes available.





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      NOTE: For example, an incomplete validation may be because all the
      required certificates are not available or the grace period is not
      completed.

   A valid response indicates that the signature has passed
   verification, and it complies with the signature validation policy.

   Example validation sequences are illustrated in Annex B.

<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>.  Electronic Signature Attributes</span>

   This section builds upon the existing Cryptographic Message Syntax
   (CMS), as defined in <a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>], and Enhanced Security Services
   (ESS), as defined in <a href="./rfc2634">RFC 2634</a> [<a href="#ref-5" title="&quot;Enhanced Security Services for S/MIME&quot;">5</a>].  The overall structure of an
   Electronic Signature is as defined in CMS.  The Electronic Signature
   (ES) uses attributes defined in CMS, ESS, and the present document.
   The present document defines ES attributes that it uses and that are
   not defined elsewhere.

   The mandated set of attributes and the digital signature value is
   defined as the minimum Electronic Signature (ES) required by the
   present document.  A signature policy may mandate that other signed
   attributes be present.

<span class="h3"><a class="selflink" id="section-5.1" href="#section-5.1">5.1</a>.  General Syntax</span>

   The general syntax of the ES is as defined in CMS (<a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]).

      NOTE: CMS defines content types for id-data, id-signedData,
      id-envelopedData, id-digestedData, id-encryptedData, and
      id-authenticatedData.  Although CMS permits other documents to
      define other content types, the ASN.1 type defined should not be a
      CHOICE type.  The present document does not define other content
      types.

<span class="h3"><a class="selflink" id="section-5.2" href="#section-5.2">5.2</a>.  Data Content Type</span>

   The data content type of the ES is as defined in CMS (<a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]).

      NOTE: If the content type is id-data, it is recommended that the
      content be encoded using MIME, and that the MIME type is used to
      identify the presentation format of the data.  See Annex F.1 for
      an example of using MIME to identify the encoding type.

<span class="h3"><a class="selflink" id="section-5.3" href="#section-5.3">5.3</a>.  Signed-data Content Type</span>

   The Signed-data content type of the ES is as defined in CMS (<a href="./rfc3852">RFC 3852</a>
   [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]).



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<span class="h3"><a class="selflink" id="section-5.4" href="#section-5.4">5.4</a>.  SignedData Type</span>

   The syntax of the SignedData of the ES is as defined in CMS (<a href="./rfc3852">RFC 3852</a>
   [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]).

   The fields of type SignedData are as defined in CMS (<a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]).

   The identification of a signer's certificate used to create the
   signature is always signed (see <a href="#section-5.7.3">Section 5.7.3</a>).  The validation
   policy may specify requirements for the presence of certain
   certificates.  The degenerate case, where there are no signers, is
   not valid in the present document.

<span class="h3"><a class="selflink" id="section-5.5" href="#section-5.5">5.5</a>.  EncapsulatedContentInfo Type</span>

   The syntax of the EncapsulatedContentInfo type ES is as defined in
   CMS (<a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]).

   For the purpose of long-term validation, as defined by the present
   document, it is advisable that either the eContent is present, or the
   data that is signed is archived in such as way as to preserve any
   data encoding.  It is important that the OCTET STRING used to
   generate the signature remains the same every time either the
   verifier or an arbitrator validates the signature.

      NOTE: The eContent is optional in CMS :

          - When it is present, this allows the signed data to be
            encapsulated in the SignedData structure, which then
            contains both the signed data and the signature.  However,
            the signed data may only be accessed by a verifier able to
            decode the ASN.1 encoded SignedData structure.

          - When it is missing, this allows the signed data to be sent
            or stored separately from the signature, and the SignedData
            structure only contains the signature.  It is, in the case
            of the signature, only the data that is signed that needs to
            be stored and distributed in such as way as to preserve any
            data encoding.

   The degenerate case where there are no signers is not valid in the
   present document.

<span class="h3"><a class="selflink" id="section-5.6" href="#section-5.6">5.6</a>.  SignerInfo Type</span>

   The syntax of the SignerInfo type ES is as defined in CMS (<a href="./rfc3852">RFC 3852</a>
   [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]).




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   Per-signer information is represented in the type SignerInfo.  In the
   case of multiple independent signatures (see Annex B.5), there is an
   instance of this field for each signer.

   The fields of type SignerInfo have the meanings defined in CMS (<a href="./rfc3852">RFC</a>
   <a href="./rfc3852">3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]), but the signedAttrs field shall contain the following
   attributes:

      - content-type, as defined in <a href="#section-5.7.1">Section 5.7.1</a>; and

      - message-digest, as defined in <a href="#section-5.7.2">Section 5.7.2</a>;

      - signing-certificate, as defined in <a href="#section-5.7.3">Section 5.7.3</a>.

<span class="h4"><a class="selflink" id="section-5.6.1" href="#section-5.6.1">5.6.1</a>.  Message Digest Calculation Process</span>

   The message digest calculation process is as defined in CMS (<a href="./rfc3852">RFC 3852</a>
   [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]).

<span class="h4"><a class="selflink" id="section-5.6.2" href="#section-5.6.2">5.6.2</a>.  Message Signature Generation Process</span>

   The input to the message signature generation process is as defined
   in CMS (<a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]).

<span class="h4"><a class="selflink" id="section-5.6.3" href="#section-5.6.3">5.6.3</a>.  Message Signature Verification Process</span>

   The procedures for message signature verification are defined in CMS
   (<a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]) and enhanced in the present document: the input to the
   signature verification process must be the signer's public key, which
   shall be verified as correct using the signing certificate reference
   attribute containing a reference to the signing certificate, i.e.,
   when SigningCertificateV2 from <a href="./rfc5035">RFC 5035</a> [<a href="#ref-16" title="&quot;Information technology ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)&quot;">16</a>] or SigningCertificate
   from ESS [<a href="#ref-5" title="&quot;Enhanced Security Services for S/MIME&quot;">5</a>] is used, the public key from the first certificate
   identified in the sequence of certificate identifiers from
   SigningCertificate must be the key used to verify the digital
   signature.

<span class="h3"><a class="selflink" id="section-5.7" href="#section-5.7">5.7</a>.  Basic ES Mandatory Present Attributes</span>

   The following attributes shall be present with the signed-data
   defined by the present document.  The attributes are defined in CMS
   (<a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]).

<span class="h4"><a class="selflink" id="section-5.7.1" href="#section-5.7.1">5.7.1</a>.  content-type</span>

   The content-type attribute indicates the type of the signed content.
   The syntax of the content-type attribute type is as defined in CMS
   (<a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]) <a href="#section-11.1">Section 11.1</a>.



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      NOTE 1: As stated in <a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>] , the content-type attribute
      must have its value (i.e., ContentType) equal to the eContentType
      of the EncapsulatedContentInfo value being signed.

      NOTE 2: For implementations supporting signature generation, if
      the content-type attribute is id-data, then it is recommended that
      the eContent be encoded using MIME.  For implementations
      supporting signature verification, if the signed data (i.e.,
      eContent) is MIME-encoded, then the OID of the content-type
      attribute must be id-data.  In both cases, the MIME
      content-type(s) must be used to identify the presentation format
      of the data.  See Annex F for further details about the use of
      MIME.

<span class="h4"><a class="selflink" id="section-5.7.2" href="#section-5.7.2">5.7.2</a>.  Message Digest</span>

   The syntax of the message-digest attribute type of the ES is as
   defined in CMS (<a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]).

<span class="h4"><a class="selflink" id="section-5.7.3" href="#section-5.7.3">5.7.3</a>.  Signing Certificate Reference Attributes</span>

   The Signing certificate reference attributes are supported by using
   either the ESS signing-certificate attribute or the
   ESS-signing-certificate-v2 attribute.

   These attributes shall contain a reference to the signer's
   certificate; they are designed to prevent simple substitution and
   reissue attacks and to allow for a restricted set of certificates to
   be used in verifying a signature.  They have a compact form (much
   shorter than the full certificate) that allows for a certificate to
   be unambiguously identified.

   One, and only one, of the following alternative attributes shall be
   present with the signedData, defined by the present document:

      - The ESS signing-certificate attribute, defined in ESS [<a href="#ref-5" title="&quot;Enhanced Security Services for S/MIME&quot;">5</a>], must
        be used if the SHA-1 hashing algorithm is used.

      - The ESS signing-certificate-v2 attribute, defined in "ESS
        Update: Adding CertID Algorithm Agility", <a href="./rfc5035">RFC 5035</a> [<a href="#ref-15" title="&quot;Enhanced Security Services (ESS) Update: Adding CertID Algorithm Agility&quot;">15</a>], which
        shall be used when other hashing algorithms are to be used.

   The certificate to be used to verify the signature shall be
   identified in the sequence (i.e., the certificate from the signer),
   and the sequence shall not be empty.  The signature validation policy
   may mandate other certificates be present that may include all the
   certificates up to the trust anchor.




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<span class="h5"><a class="selflink" id="section-5.7.3.1" href="#section-5.7.3.1">5.7.3.1</a>.  ESS signing-certificate Attribute Definition</span>

   The syntax of the signing-certificate attribute type of the ES is as
   defined in Enhanced Security Services (ESS), <a href="./rfc2634">RFC 2634</a> [<a href="#ref-5" title="&quot;Enhanced Security Services for S/MIME&quot;">5</a>], and
   further qualified in the present document.

   The sequence of the policy information field is not used in the
   present document.

   The ESS signing-certificate attribute shall be a signed attribute.
   The encoding of the ESSCertID for this certificate shall include the
   issuerSerial field.

   If present, the issuerAndSerialNumber in SignerIdentifier field of
   the SignerInfo shall match the issuerSerial field present in
   ESSCertID.  In addition, the certHash from ESSCertID shall match the
   SHA-1 hash of the certificate.  The certificate identified shall be
   used during the signature verification process.  If the hash of the
   certificate does not match the certificate used to verify the
   signature, the signature shall be considered invalid.

      NOTE: Where an attribute certificate is used by the signer to
      associate a role, or other attributes of the signer, with the
      electronic signature; this is placed in the signer-attributes
      attribute as defined in <a href="#section-5.8.3">Section 5.8.3</a>.

<span class="h5"><a class="selflink" id="section-5.7.3.2" href="#section-5.7.3.2">5.7.3.2</a>.  ESS signing-certificate-v2 Attribute Definition</span>

   The ESS signing-certificate-v2 attribute is similar to the ESS
   signing-certificate defined above, except that this attribute can be
   used with hashing algorithms other than SHA-1.

   The syntax of the signing-certificate-v2 attribute type of the ES is
   as defined in "ESS Update: Adding CertID Algorithm Agility", <a href="./rfc5035">RFC 5035</a>
   [<a href="#ref-15" title="&quot;Enhanced Security Services (ESS) Update: Adding CertID Algorithm Agility&quot;">15</a>], and further qualified in the present document.

   The sequence of the policy information field is not used in the
   present document.

   This attribute shall be used in the same manner as defined above for
   the ESS signing-certificate attribute.

   The object identifier for this attribute is:
         id-aa-signingCertificateV2 OBJECT IDENTIFIER ::=
         { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
           smime(16) id-aa(2) 47 }





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   If present, the issuerAndSerialNumber in SignerIdentifier field of
   the SignerInfo shall match the issuerSerial field present in
   ESSCertIDv2.  In addition, the certHash from ESSCertIDv2 shall match
   the hash of the certificate computed using the hash function
   specified in the hashAlgorithm field.  The certificate identified
   shall be used during the signature verification process.  If the hash
   of the certificate does not match the certificate used to verify the
   signature, the signature shall be considered invalid.

      NOTE 1: Where an attribute certificate is used by the signer to
      associate a role, or other attributes of the signer, with the
      electronic signature; this is placed in the signer-attributes
      attribute as defined in <a href="#section-5.8.3">Section 5.8.3</a>.

      NOTE 2: <a href="./rfc3126">RFC 3126</a> was using the other signing-certificate attribute
      (see <a href="#section-5.7.3.3">Section 5.7.3.3</a>) for the same purpose.  Its use is now
      deprecated, since this structure is simpler.

<span class="h5"><a class="selflink" id="section-5.7.3.3" href="#section-5.7.3.3">5.7.3.3</a>.  Other signing-certificate Attribute Definition</span>

   <a href="./rfc3126">RFC 3126</a> was using the other signing-certificate attribute as an
   alternative to the ESS signing-certificate when hashing algorithms
   other than SHA-1 were being used.  Its use is now deprecated, since
   the structure of the signing-certificate-v2 attribute is simpler.
   Its description is however still present in this version for
   backwards compatibility.

   id-aa-ets-otherSigCert OBJECT IDENTIFIER ::= { iso(1)
       member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
       smime(16) id-aa(2) 19 }

   The other-signing-certificate attribute value has the ASN.1 syntax
   OtherSigningCertificate:

   OtherSigningCertificate ::=  SEQUENCE {
       certs        SEQUENCE OF OtherCertID,
       policies     SEQUENCE OF PolicyInformation OPTIONAL
                    -- NOT USED IN THE PRESENT DOCUMENT }

   OtherCertID ::= SEQUENCE {
       otherCertHash            OtherHash,
       issuerSerial             IssuerSerial OPTIONAL }

   OtherHash ::= CHOICE {
       sha1Hash OtherHashValue,  -- This contains a SHA-1 hash
       otherHash OtherHashAlgAndValue}

   OtherHashValue ::= OCTET STRING



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   OtherHashAlgAndValue ::= SEQUENCE {
       hashAlgorithm     AlgorithmIdentifier,
       hashValue         OtherHashValue }

<span class="h3"><a class="selflink" id="section-5.8" href="#section-5.8">5.8</a>.  Additional Mandatory Attributes for Explicit Policy-based</span>
<span class="h3">      Electronic Signatures</span>

<span class="h4"><a class="selflink" id="section-5.8.1" href="#section-5.8.1">5.8.1</a>.  signature-policy-identifier</span>

   The present document mandates that for CAdES-EPES, a reference to the
   signature policy is included in the signedData.  This reference is
   explicitly identified.  A signature policy defines the rules for
   creation and validation of an electronic signature, and is included
   as a signed attribute with every Explicit Policy-based Electronic
   Signature.  The signature-policy-identifier shall be a signed
   attribute.

   The following object identifier identifies the
   signature-policy-identifier attribute:

      id-aa-ets-sigPolicyId OBJECT IDENTIFIER ::= { iso(1)
      member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
      smime(16) id-aa(2) 15 }

   signature-policy-identifier attribute values have ASN.1 type
   SignaturePolicyIdentifier:

      SignaturePolicyIdentifier ::= CHOICE {
           signaturePolicyId          SignaturePolicyId,
           signaturePolicyImplied     SignaturePolicyImplied
                                      -- not used in this version
   }

      SignaturePolicyId ::= SEQUENCE {
           sigPolicyId           SigPolicyId,
           sigPolicyHash         SigPolicyHash,
           sigPolicyQualifiers   SEQUENCE SIZE (1..MAX) OF
                                   SigPolicyQualifierInfo OPTIONAL}

      SignaturePolicyImplied ::= NULL











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   The sigPolicyId field contains an object-identifier that uniquely
   identifies a specific version of the signature policy.  The syntax of
   this field is as follows:

      SigPolicyId ::= OBJECT IDENTIFIER

   The sigPolicyHash field optionally contains the identifier of the
   hash algorithm and the hash of the value of the signature policy.
   The hashValue within the sigPolicyHash may be set to zero to indicate
   that the policy hash value is not known.

      NOTE: The use of a zero sigPolicyHash value is to ensure backwards
      compatibility with earlier versions of the current document.  If
      sigPolicyHash is zero, then the hash value should not be checked
      against the calculated hash value of the signature policy.

   If the signature policy is defined using ASN.1, then the hash is
   calculated on the value without the outer type and length fields, and
   the hashing algorithm shall be as specified in the field
   sigPolicyHash.

   If the signature policy is defined using another structure, the type
   of structure and the hashing algorithm shall be either specified as
   part of the signature policy, or indicated using a signature policy
   qualifier.

      SigPolicyHash ::= OtherHashAlgAndValue

      OtherHashAlgAndValue ::= SEQUENCE {
         hashAlgorithm   AlgorithmIdentifier,
         hashValue       OtherHashValue }

      OtherHashValue ::= OCTET STRING

   A Signature Policy Identifier may be qualified with other information
   about the qualifier.  The semantics and syntax of the qualifier is as
   associated with the object-identifier in the sigPolicyQualifierId
   field.  The general syntax of this qualifier is as follows:

      SigPolicyQualifierInfo ::= SEQUENCE {
           sigPolicyQualifierId  SigPolicyQualifierId,
           sigQualifier          ANY DEFINED BY sigPolicyQualifierId }









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   The present document specifies the following qualifiers:

      - spuri: this contains the web URI or URL reference to the
        signature policy, and

      - sp-user-notice: this contains a user notice that should be
        displayed whenever the signature is validated.

           sigpolicyQualifierIds defined in the present document:
           SigPolicyQualifierId ::= OBJECT IDENTIFIER

            id-spq-ets-uri OBJECT IDENTIFIER ::= { iso(1)
            member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
            smime(16) id-spq(5) 1 }

        SPuri ::= IA5String

            id-spq-ets-unotice OBJECT IDENTIFIER ::= { iso(1)
            member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
            smime(16) id-spq(5) 2 }

        SPUserNotice ::= SEQUENCE {
                noticeRef        NoticeReference OPTIONAL,
                explicitText     DisplayText OPTIONAL}

        NoticeReference ::= SEQUENCE {

                organization     DisplayText,
                noticeNumbers    SEQUENCE OF INTEGER }

        DisplayText ::= CHOICE {
                visibleString    VisibleString  (SIZE (1..200)),
                bmpString        BMPString      (SIZE (1..200)),
                utf8String       UTF8String     (SIZE (1..200)) }

<span class="h3"><a class="selflink" id="section-5.9" href="#section-5.9">5.9</a>.  CMS Imported Optional Attributes</span>

   The following attributes may be present with the signed-data; the
   attributes are defined in CMS (<a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]) and are imported into
   the present document.  Where appropriate, the attributes are
   qualified and profiled by the present document.

<span class="h4"><a class="selflink" id="section-5.9.1" href="#section-5.9.1">5.9.1</a>.  signing-time</span>

   The signing-time attribute specifies the time at which the signer
   claims to have performed the signing process.





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   Signing-time attribute values for ES have the ASN.1 type SigningTime
   as defined in CMS (<a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]).

      NOTE: <a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>] states that dates between January 1, 1950 and
      December 31, 2049 (inclusive) must be encoded as UTCTime.  Any
      dates with year values before 1950 or after 2049 must be encoded
      as GeneralizedTime.

<span class="h4"><a class="selflink" id="section-5.9.2" href="#section-5.9.2">5.9.2</a>.  countersignature</span>

   The countersignature attribute values for ES have ASN.1 type
   CounterSignature, as defined in CMS (<a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]).  A
   countersignature attribute shall be an unsigned attribute.

<span class="h3"><a class="selflink" id="section-5.10" href="#section-5.10">5.10</a>.  ESS-Imported Optional Attributes</span>

   The following attributes may be present with the signed-data defined
   by the present document.  The attributes are defined in ESS and are
   imported into the present document and are appropriately qualified
   and profiled by the present document.

<span class="h4"><a class="selflink" id="section-5.10.1" href="#section-5.10.1">5.10.1</a>.  content-reference Attribute</span>

   The content-reference attribute is a link from one SignedData to
   another.  It may be used to link a reply to the original message to
   which it refers, or to incorporate by reference one SignedData into
   another.  The content-reference attribute shall be a signed
   attribute.

   content-reference attribute values for ES have ASN.1 type
   ContentReference, as defined in ESS (<a href="./rfc2634">RFC 2634</a> [<a href="#ref-5" title="&quot;Enhanced Security Services for S/MIME&quot;">5</a>]).

   The content-reference attribute shall be used as defined in ESS (<a href="./rfc2634">RFC</a>
   <a href="./rfc2634">2634</a> [<a href="#ref-5" title="&quot;Enhanced Security Services for S/MIME&quot;">5</a>]).

<span class="h4"><a class="selflink" id="section-5.10.2" href="#section-5.10.2">5.10.2</a>.  content-identifier Attribute</span>

   The content-identifier attribute provides an identifier for the
   signed content, for use when a reference may be later required to
   that content; for example, in the content-reference attribute in
   other signed data sent later.  The content-identifier shall be a
   signed attribute.

   content-identifier attribute type values for the ES have an ASN.1
   type ContentIdentifier, as defined in ESS (<a href="./rfc2634">RFC 2634</a> [<a href="#ref-5" title="&quot;Enhanced Security Services for S/MIME&quot;">5</a>]).

   The minimal content-identifier attribute should contain a
   concatenation of user-specific identification information (such as a



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   user name or public keying material identification information), a
   GeneralizedTime string, and a random number.

<span class="h4"><a class="selflink" id="section-5.10.3" href="#section-5.10.3">5.10.3</a>.  content-hints Attribute</span>

   The content-hints attribute provides information on the innermost
   signed content of a multi-layer message where one content is
   encapsulated in another.

   The syntax of the content-hints attribute type of the ES is as
   defined in ESS (<a href="./rfc2634">RFC 2634</a> [<a href="#ref-5" title="&quot;Enhanced Security Services for S/MIME&quot;">5</a>]).

   When used to indicate the precise format of the data to be presented
   to the user, the following rules apply:

      - the contentType indicates the type of the associated content.
        It is an object identifier (i.e., a unique string of integers)
        assigned by an authority that defines the content type; and

      - when the contentType is id-data, the contentDescription shall
        define the presentation format; the format may be defined by
        MIME types.

   When the format of the content is defined by MIME types, the
   following rules apply:

      - the contentType shall be id-data, as defined in CMS (<a href="./rfc3852">RFC 3852</a>
        [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]);

      - the contentDescription shall be used to indicate the encoding of
        the data, in accordance with the rules defined <a href="./rfc2045">RFC 2045</a> [<a href="#ref-6" title="&quot;Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies&quot;">6</a>]; see
        Annex F for an example of structured contents and MIME.

   NOTE 1: id-data OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
   rsadsi(113549) pkcs(1) pkcs7(7) 1 }

   NOTE 2: contentDescription is optional in ESS (<a href="./rfc2634">RFC 2634</a> [<a href="#ref-5" title="&quot;Enhanced Security Services for S/MIME&quot;">5</a>]).  It may
   be used to complement contentTypes defined elsewhere; such
   definitions are outside the scope of the present document.

<span class="h3"><a class="selflink" id="section-5.11" href="#section-5.11">5.11</a>.  Additional Optional Attributes Defined in the Present Document</span>

   This section defines a number of attributes that may be used to
   indicate additional information to a verifier:

      a) the type of commitment from the signer, and/or

      b) the claimed location where the signature is performed, and/or



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      c) claimed attributes or certified attributes of the signer,
         and/or

      d) a content time-stamp applied before the content was signed.

<span class="h4"><a class="selflink" id="section-5.11.1" href="#section-5.11.1">5.11.1</a>.  commitment-type-indication Attribute</span>

   There may be situations where a signer wants to explicitly indicate
   to a verifier that by signing the data, it illustrates a type of
   commitment on behalf of the signer.  The commitment-type-indication
   attribute conveys such information.

   The commitment-type-indication attribute shall be a signed attribute.
   The commitment type may be:

      - defined as part of the signature policy, in which case, the
        commitment type has precise semantics that are defined as part
        of the signature policy; and

      - be a registered type, in which case, the commitment type has
        precise semantics defined by registration, under the rules of
        the registration authority.  Such a registration authority may
        be a trading association or a legislative authority.

   The signature policy specifies a set of attributes that it
   "recognizes".  This "recognized" set includes all those commitment
   types defined as part of the signature policy, as well as any
   externally defined commitment types that the policy may choose to
   recognize.  Only recognized commitment types are allowed in this
   field.

   The following object identifier identifies the
   commitment-type-indication attribute:

id-aa-ets-commitmentType OBJECT IDENTIFIER ::= { iso(1) member-body(2)
    us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 16}

commitment-type-indication attribute values have ASN.1 type
CommitmentTypeIndication.

CommitmentTypeIndication ::= SEQUENCE {
  commitmentTypeId CommitmentTypeIdentifier,
  commitmentTypeQualifier SEQUENCE SIZE (1..MAX) OF
                 CommitmentTypeQualifier OPTIONAL}

CommitmentTypeIdentifier ::= OBJECT IDENTIFIER





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CommitmentTypeQualifier ::= SEQUENCE {
   commitmentTypeIdentifier   CommitmentTypeIdentifier,
   qualifier                  ANY DEFINED BY commitmentTypeIdentifier }

   The use of any qualifiers to the commitment type is outside the scope
   of the present document.

   The following generic commitment types are defined in the present
   document:

id-cti-ets-proofOfOrigin OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) cti(6) 1}

id-cti-ets-proofOfReceipt OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) cti(6) 2}

id-cti-ets-proofOfDelivery OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
cti(6) 3}

id-cti-ets-proofOfSender OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) cti(6) 4}

id-cti-ets-proofOfApproval OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
cti(6) 5}

id-cti-ets-proofOfCreation OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
cti(6) 6}

   These generic commitment types have the following meanings:

   Proof of origin indicates that the signer recognizes to have created,
   approved, and sent the message.

   Proof of receipt indicates that signer recognizes to have received
   the content of the message.

   Proof of delivery indicates that the TSP providing that indication
   has delivered a message in a local store accessible to the recipient
   of the message.

   Proof of sender indicates that the entity providing that indication
   has sent the message (but not necessarily created it).

   Proof of approval indicates that the signer has approved the content
   of the message.



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   Proof of creation indicates that the signer has created the message
   (but not necessarily approved, nor sent it).

<span class="h4"><a class="selflink" id="section-5.11.2" href="#section-5.11.2">5.11.2</a>.  signer-location Attribute</span>

   The signer-location attribute specifies a mnemonic for an address
   associated with the signer at a particular geographical (e.g., city)
   location.  The mnemonic is registered in the country in which the
   signer is located and is used in the provision of the Public Telegram
   Service (according to ITU-T Recommendation F.1 [<a href="#ref-11" title="&quot;Operational provisions for the international public telegram service&quot;">11</a>]).

   The signer-location attribute shall be a signed attribute.  The
   following object identifier identifies the signer-location attribute:

id-aa-ets-signerLocation OBJECT IDENTIFIER ::= { iso(1) member-body(2)
    us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 17}

   Signer-location attribute values have ASN.1 type SignerLocation:

SignerLocation ::= SEQUENCE {
   -- at least one of the following shall be present:
      countryName    [0]    DirectoryString OPTIONAL,
                            -- As used to name a Country in X.500
      localityName   [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>]    DirectoryString OPTIONAL,
                            -- As used to name a locality in X.500
      postalAdddress [<a href="#ref-2" title="&quot;Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile&quot;">2</a>]    PostalAddress OPTIONAL }

PostalAddress ::= SEQUENCE SIZE(1..6) OF DirectoryString

<span class="h4"><a class="selflink" id="section-5.11.3" href="#section-5.11.3">5.11.3</a>.  signer-attributes Attribute</span>

   The signer-attributes attribute specifies additional attributes of
   the signer (e.g., role).  It may be either:

      - claimed attributes of the signer; or

      - certified attributes of the signer.

   The signer-attributes attribute shall be a signed attribute.  The
   following object identifier identifies the signer-attribute
   attribute:

   id-aa-ets-signerAttr OBJECT IDENTIFIER ::= { iso(1) member-body(2)
       us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 18}







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   signer-attributes values have ASN.1 type SignerAttribute:

   SignerAttribute ::= SEQUENCE OF CHOICE {
       claimedAttributes     [0]   ClaimedAttributes,
       certifiedAttributes   [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>]   CertifiedAttributes }

   ClaimedAttributes ::= SEQUENCE OF Attribute

   CertifiedAttributes ::= AttributeCertificate
   -- as defined in <a href="./rfc3281">RFC 3281</a>: see <a href="#section-4.1">Section 4.1</a>.

      NOTE 1: Only a single signer-attributes can be used.

      NOTE 2: Attribute and AttributeCertificate are as defined
      respectively in ITU-T Recommendations X.501 [<a href="#ref-9" title="&quot;Information technology - Open Systems Interconnection - Directory models&quot;">9</a>] and X.509 [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>].

<span class="h4"><a class="selflink" id="section-5.11.4" href="#section-5.11.4">5.11.4</a>.  content-time-stamp Attribute</span>

   The content-time-stamp attribute is an attribute that is the
   time-stamp token of the signed data content before it is signed.  The
   content-time-stamp attribute shall be a signed attribute.

   The following object identifier identifies the content-time-stamp
   attribute:

   id-aa-ets-contentTimestamp OBJECT IDENTIFIER ::=
   { iso(1) member- body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
   smime(16) id-aa(2) 20}

   content-time-stamp attribute values have ASN.1 type ContentTimestamp:
   ContentTimestamp ::= TimeStampToken

   The value of messageImprint of TimeStampToken (as described in <a href="./rfc3161">RFC</a>
   <a href="./rfc3161">3161</a> [<a href="#ref-7" title="&quot;Internet X.509 Public Key Infrastructure Time-Stamp Protocol (TSP)&quot;">7</a>]) shall be a hash of the value of the eContent field within
   encapContentInfo in the signedData.

   For further information and definition of TimeStampToken, see <a href="#section-7.4">Section</a>
   <a href="#section-7.4">7.4</a>.

      NOTE: content-time-stamp indicates that the signed information was
      formed before the date included in the content-time-stamp.

<span class="h3"><a class="selflink" id="section-5.12" href="#section-5.12">5.12</a>.  Support for Multiple Signatures</span>

<span class="h4"><a class="selflink" id="section-5.12.1" href="#section-5.12.1">5.12.1</a>.  Independent Signatures</span>

   Multiple independent signatures (see Annex B.5) are supported by
   independent SignerInfo from each signer.



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   Each SignerInfo shall include all the attributes required under the
   present document and shall be processed independently by the
   verifier.

      NOTE: Independent signatures may be used to provide independent
      signatures from different parties with different signed
      attributes, or to provide multiple signatures from the same party
      using alternative signature algorithms, in which case the other
      attributes, excluding time values and signature policy
      information, will generally be the same.

<span class="h4"><a class="selflink" id="section-5.12.2" href="#section-5.12.2">5.12.2</a>.  Embedded Signatures</span>

   Multiple embedded signatures (see Annex C.5) are supported using the
   countersignature unsigned attribute (see <a href="#section-5.9.2">Section 5.9.2</a>).  Each
   counter signature is carried in countersignature held as an unsigned
   attribute to the SignerInfo to which the counter-signature is
   applied.

      NOTE: Counter signatures may be used to provide signatures from
      different parties with different signed attributes, or to provide
      multiple signatures from the same party using alternative
      signature algorithms, in which case the other attributes,
      excluding time values and signature policy information, will
      generally be the same.

<span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a>.  Additional Electronic Signature Validation Attributes</span>

   This section specifies attributes that contain different types of
   validation data.  These attributes build on the electronic signature
   specified in <a href="#section-5">Section 5</a>.  This includes:

      - Signature-time-stamp applied to the electronic signature value
        or a Time-Mark in an audit trail.  This is defined as the
        Electronic Signature with Time (CAdES-T); and

      - Complete validation data references that comprise the time-stamp
        of the signature value, plus references to all the certificates
        (complete-certificate-references) and revocation (complete-
        revocation-references) information used for full validation of
        the electronic signature.  This is defined as the Electronic
        Signature with Complete data references (CAdES-C).

      NOTE 1: Formats for CAdES-T are illustrated in <a href="#section-4.4">Section 4.4</a>, and
      the attributes are defined in <a href="#section-6.1.1">Section 6.1.1</a>.






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      NOTE 2: Formats for CAdES-C are illustrated in <a href="#section-4.4">Section 4.4</a>.  The
      required attributes for the CAdES-C signature format are defined
      in Sections <a href="#section-6.2.1">6.2.1</a> to <a href="#section-6.2.2">6.2.2</a>; optional attributes are defined in
      Sections <a href="#section-6.2.3">6.2.3</a> and <a href="#section-6.2.4">6.2.4</a>.

   In addition, the following optional extended forms of validation data
   are also defined; see Annex B for an overview of the extended forms
   of validation data:

      - CAdES-X with time-stamp: there are two types of time-stamps used
        in extended validation data defined by the present document;

         - Type 1(CAdES-X Type 1): comprises a time-stamp over the ES
           with Complete validation data (CAdES-C); and

         - Type 2 (CAdES-X Type2): comprises a time-stamp over the
           certification path references and the revocation information
           references used to support the CAdES-C.

      NOTE 3: Formats for CAdES-X Type 1 and CAdES-X Type 2 are
      illustrated in Sections B.1.2 and B.1.3, respectively.

         - CAdES-X Long: comprises the Complete validation data
           references (CAdES-C), plus the actual values of all the
           certificates and revocation information used in the CAdES-C.

      NOTE 4: Formats for CAdES-X Long are illustrated in Annex B.1.1.

         - CAdES-X Long Type 1 or CAdES-X Long Type 2: comprises an
           X-Time-Stamp (Type 1 or Type 2), plus the actual values of
           all the certificates and revocation information used in the
           CAdES-C as per CAdES-X Long.

   This section also specifies the data structures used in Archive
   validation data format (CAdES-A)of extended forms:

      - Archive form of electronic signature (CAdES-A) comprises:

        - the Complete validation data references (CAdES-C),

        - the certificate and revocation values (as in a CAdES-X Long ),

        - any existing extended electronic signature time-stamps
          (CAdES-X Type 1 or CAdES-X Type 2), if present, and

        - the signed user data and an additional archive time-stamp
          applied over all that data.




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        An archive time-stamp may be repeatedly applied after long
        periods to maintain validity when electronic signature and
        time-stamping algorithms weaken.

   The additional data required to create the forms of electronic
   signature identified above is carried as unsigned attributes
   associated with an individual signature by being placed in the
   unsignedAttrs field of SignerInfo.  Thus, all the attributes defined
   in <a href="#section-6">Section 6</a> are unsigned attributes.

      NOTE 5: Where multiple signatures are to be supported, as
      described in <a href="#section-5.12">Section 5.12</a>, each signature has a separate
      SignerInfo.  Thus, each signature requires its own unsigned
      attribute values to create CAdES-T, CAdES-C, etc.

      NOTE 6: The optional attributes of the extended validation data
      are defined in Sections <a href="#section-6.3">6.3</a> and <a href="#section-6.4">6.4</a>.

<span class="h3"><a class="selflink" id="section-6.1" href="#section-6.1">6.1</a>.  signature time-stamp Attribute (CAdES-T)</span>

   An electronic signature with time-stamp is an electronic signature
   for which part, but not all, of the additional data required for
   validation is available (i.e., some certificates and revocation
   information are available, but not all).

   The minimum structure time-stamp validation data is:

      - the signature time-stamp attribute, as defined in <a href="#section-6.1.1">Section 6.1.1</a>,
        over the ES signature value.

<span class="h4"><a class="selflink" id="section-6.1.1" href="#section-6.1.1">6.1.1</a>.  signature-time-stamp Attribute Definition</span>

   The signature-time-stamp attribute is a TimeStampToken computed on
   the signature value for a specific signer; it is an unsigned
   attribute.  Several instances of this attribute may occur with an
   electronic signature, from different TSAs.

   The following object identifier identifies the signature-time-stamp
   attribute:

   id-aa-signatureTimeStampToken OBJECT IDENTIFIER ::=
   { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
   smime(16) id-aa(2) 14}

   The signature-time-stamp attribute value has ASN.1 type
   SignatureTimeStampToken:

   SignatureTimeStampToken ::= TimeStampToken



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   The value of the messageImprint field within TimeStampToken shall be
   a hash of the value of the signature field within SignerInfo for the
   signedData being time-stamped.

   For further information and definition of TimeStampToken, see <a href="#section-7.4">Section</a>
   <a href="#section-7.4">7.4</a>.

      NOTE 1: In the case of multiple signatures, it is possible to have
      a:

      - TimeStampToken computed for each and all signers; or

      - TimeStampToken computed on one signer's signature; and no

      - TimeStampToken on another signer's signature.

      NOTE 2: In the case of multiple signatures, several TSTs, issued
      by different TSAs, may be present within the same signerInfo (see
      <a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]).

<span class="h3"><a class="selflink" id="section-6.2" href="#section-6.2">6.2</a>.  Complete Validation Data References (CAdES-C)</span>

   An electronic signature with Complete validation data references
   (CAdES-C) is an electronic signature for which all the additional
   data required for validation (i.e., all certificates and revocation
   information) is available.  This form is built on the CAdES-T form
   defined above.

   As a minimum, the Complete validation data shall include the
   following:

      - a time, which shall either be a signature-timestamp attribute,
        as defined in <a href="#section-6.1.1">Section 6.1.1</a>, or a time-mark operated by a
        Time-Marking Authority;

      - complete-certificate-references, as defined in <a href="#section-6.2.1">Section 6.2.1</a>;

      - complete-revocation-references, as defined in <a href="#section-6.2.2">Section 6.2.2</a>.

<span class="h4"><a class="selflink" id="section-6.2.1" href="#section-6.2.1">6.2.1</a>.  complete-certificate-references Attribute Definition</span>

   The complete-certificate-references attribute is an unsigned
   attribute.  It references the full set of CA certificates that have
   been used to validate an ES with Complete validation data up to (but
   not including) the signer's certificate.  Only a single instance of
   this attribute shall occur with an electronic signature.





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      NOTE 1: The signer's certificate is referenced in the signing
      certificate attribute (see <a href="#section-5.7.3">Section 5.7.3</a>).

id-aa-ets-certificateRefs OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 21}

   The complete-certificate-references attribute value has the ASN.1
   syntax CompleteCertificateRefs.

   CompleteCertificateRefs ::=  SEQUENCE OF OtherCertID

   OtherCertID is defined in <a href="#section-5.7.3.3">Section 5.7.3.3</a>.

   The IssuerSerial that shall be present in OtherCertID.  The certHash
   shall match the hash of the certificate referenced.

      NOTE 2: Copies of the certificate values may be held using the
      certificate-values attribute, defined in <a href="#section-6.3.3">Section 6.3.3</a>.

      This attribute may include references to the certification chain
      for any TSUs that provides time-stamp tokens.  In this case, the
      unsigned attribute shall be added to the signedData of the
      relevant time-stamp token as an unsignedAttrs in the signerInfos
      field.

<span class="h4"><a class="selflink" id="section-6.2.2" href="#section-6.2.2">6.2.2</a>.  complete-revocation-references Attribute Definition</span>

   The complete-revocation-references attribute is an unsigned
   attribute.  Only a single instance of this attribute shall occur with
   an electronic signature.  It references the full set of the CRL,
   ACRL, or OCSP responses that have been used in the validation of the
   signer, and CA certificates used in ES with Complete validation data.

   This attribute indicates that the verifier has taken due diligence to
   gather the available revocation information.  The references stored
   in this attribute can be used to retrieve the referenced information,
   if not stored in the CMS structure, but somewhere else.

   The following object identifier identifies the
   complete-revocation-references attribute:

id-aa-ets-revocationRefs OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 22}








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   The complete-revocation-references attribute value has the ASN.1
   syntax CompleteRevocationRefs:

   CompleteRevocationRefs ::=  SEQUENCE OF CrlOcspRef

   CrlOcspRef ::= SEQUENCE {
      crlids      [0]   CRLListID    OPTIONAL,
      ocspids     [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>]   OcspListID   OPTIONAL,
      otherRev    [<a href="#ref-2" title="&quot;Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile&quot;">2</a>]   OtherRevRefs OPTIONAL
   }

   CompleteRevocationRefs shall contain one CrlOcspRef for the
   signing-certificate, followed by one for each OtherCertID in the
   CompleteCertificateRefs attribute.  The second and subsequent
   CrlOcspRef fields shall be in the same order as the OtherCertID to
   which they relate.  At least one of CRLListID or OcspListID or
   OtherRevRefs should be present for all but the "trusted" CA of the
   certificate path.

CRLListID ::=  SEQUENCE {
    crls        SEQUENCE OF CrlValidatedID }

CrlValidatedID ::=  SEQUENCE {
     crlHash                   OtherHash,
     crlIdentifier             CrlIdentifier OPTIONAL }

CrlIdentifier ::= SEQUENCE {
    crlissuer                 Name,
    crlIssuedTime             UTCTime,
    crlNumber                 INTEGER OPTIONAL }

OcspListID ::=  SEQUENCE {
    ocspResponses        SEQUENCE OF OcspResponsesID }

OcspResponsesID ::=  SEQUENCE {
    ocspIdentifier              OcspIdentifier,
    ocspRepHash                 OtherHash    OPTIONAL
}

OcspIdentifier ::= SEQUENCE {
   ocspResponderID    ResponderID,
      -- As in OCSP response data
   producedAt         GeneralizedTime
   -- As in OCSP response data
}






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   When creating a crlValidatedID, the crlHash is computed over the
   entire DER encoded CRL including the signature.  The crlIdentifier
   would normally be present unless the CRL can be inferred from other
   information.

   The crlIdentifier is to identify the CRL using the issuer name and
   the CRL issued time, which shall correspond to the time thisUpdate
   contained in the issued CRL, and if present, the crlNumber.  The
   crlListID attribute is an unsigned attribute.  In the case that the
   identified CRL is a Delta CRL, then references to the set of CRLs to
   provide a complete revocation list shall be included.

   The OcspIdentifier is to identify the OCSP response using the issuer
   name and the time of issue of the OCSP response, which shall
   correspond to the time produced as contained in the issued OCSP
   response.  Since it may be needed to make the difference between two
   OCSP responses received within the same second, the hash of the
   response contained in the OcspResponsesID may be needed to solve the
   ambiguity.

      NOTE 1: Copies of the CRL and OCSP responses values may be held
      using the revocation-values attribute defined in <a href="#section-6.3.4">Section 6.3.4</a>.

      NOTE 2: It is recommended that this attribute be used in
      preference to the OtherRevocationInfoFormat specified in <a href="./rfc3852">RFC 3852</a>
      to maintain backwards compatibility with the earlier version of
      this specification.

   The syntax and semantics of other revocation references are outside
   the scope of the present document.  The definition of the syntax of
   the other form of revocation information is as identified by
   OtherRevRefType.

   This attribute may include the references to the full set of the CRL,
   ACRL, or OCSP responses that have been used to verify the
   certification chain for any TSUs that provide time-stamp tokens.  In
   this case, the unsigned attribute shall be added to the signedData of
   the relevant time-stamp token as an unsignedAttrs in the signerInfos
   field.

<span class="h4"><a class="selflink" id="section-6.2.3" href="#section-6.2.3">6.2.3</a>.  attribute-certificate-references Attribute Definition</span>

   This attribute is only used when a user attribute certificate is
   present in the electronic signature.

   The attribute-certificate-references attribute is an unsigned
   attribute.  It references the full set of AA certificates that have




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   been used to validate the attribute certificate.  Only a single
   instance of this attribute shall occur with an electronic signature.

   id-aa-ets-attrCertificateRefs OBJECT IDENTIFIER ::=
   { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
   smime(16) id-aa(2) 44}

   The attribute-certificate-references attribute value has the ASN.1
   syntax AttributeCertificateRefs:

   AttributeCertificateRefs ::=  SEQUENCE OF OtherCertID

   OtherCertID is defined in <a href="#section-5.7.3.3">Section 5.7.3.3</a>.

      NOTE: Copies of the certificate values may be held using the
      certificate-values attribute defined in <a href="#section-6.3.3">Section 6.3.3</a>.

<span class="h4"><a class="selflink" id="section-6.2.4" href="#section-6.2.4">6.2.4</a>.  attribute-revocation-references Attribute Definition</span>

   This attribute is only used when a user attribute certificate is
   present in the electronic signature and when that attribute
   certificate can be revoked.

   The attribute-revocation-references attribute is an unsigned
   attribute.  Only a single instance of this attribute shall occur with
   an electronic signature.  It references the full set of the ACRL or
   OCSP responses that have been used in the validation of the attribute
   certificate.  This attribute can be used to illustrate that the
   verifier has taken due diligence of the available revocation
   information.

   The following object identifier identifies the
   attribute-revocation-references attribute:

   id-aa-ets-attrRevocationRefs OBJECT IDENTIFIER ::= { iso(1)
   member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
   id-aa(2) 45}

   The attribute-revocation-references attribute value has the ASN.1
   syntax AttributeRevocationRefs:

   AttributeRevocationRefs ::=  SEQUENCE OF CrlOcspRef

<span class="h3"><a class="selflink" id="section-6.3" href="#section-6.3">6.3</a>.  Extended Validation Data (CAdES-X)</span>

   This section specifies a number of optional attributes that are used
   by extended forms of electronic signatures (see Annex B for an
   overview of these forms of validation data).



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<span class="h4"><a class="selflink" id="section-6.3.1" href="#section-6.3.1">6.3.1</a>.  Time-Stamped Validation Data (CAdES-X Type 1 or Type 2)</span>

   The extended validation data may include one of the following
   additional attributes, forming a CAdES-X Time-Stamp validation data
   (CAdES-X Type 1 or CAdES-X Type 2), to provide additional protection
   against later CA compromise and provide integrity of the validation
   data used:

      - CAdES-C Time-stamp, as defined in <a href="#section-6.3.5">Section 6.3.5</a> (CAdES-X Type
        1); or

      - Time-Stamped Certificates and CRLs references, as defined in
        <a href="#section-6.3.6">Section 6.3.6</a> (CAdES-X Type 2).

<span class="h4"><a class="selflink" id="section-6.3.2" href="#section-6.3.2">6.3.2</a>.  Long Validation Data (CAdES-X Long, CAdES-X Long Type 1 or 2)</span>

   The extended validation data may also include the following
   additional information, forming a CAdES-X Long, for use if later
   validation processes may not have access to this information:

      - certificate-values, as defined in <a href="#section-6.3.3">Section 6.3.3</a>; and

      - revocation-values, as defined in <a href="#section-6.3.4">Section 6.3.4</a>.

   The extended validation data may, in addition to certificate-values
   and revocation-values as defined in Sections <a href="#section-6.3.3">6.3.3</a> and <a href="#section-6.3.4">6.3.4</a>, include
   one of the following additional attributes, forming a CAdES-X Long
   Type 1 or CAdES-X Long Type 2.

      - CAdES-C Time-stamp, as defined in <a href="#section-6.3.3">Section 6.3.3</a> (CAdES-X long
        Type 1); or

      - Time-Stamped Certificates and CRLs references, as defined in
        <a href="#section-6.3.4">Section 6.3.4</a> (CAdES-X Long Type 2).

   The CAdES-X Long Type 1 or CAdES-X Long Type 2 provides additional
   protection against later CA compromise and provides integrity of the
   validation data used.

      NOTE 1: The CAdES-X-Long signature provides long-term proof of the
      validity of the signature for as long as the CA keys, CRL Issuers
      keys, and OCSP responder keys are not compromised and are
      resistant to cryptographic attacks.

      NOTE 2: As long as the time-stamp data remains valid, the CAdES-X
      Long Type 1 and the CAdES-X Long Type 2 provide the following
      important property for long-standing signatures; that having been
      found once to be valid, it shall continue to be so months or years



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      later, long after the validity period of the certificates has
      expired, or after the user key has been compromised.

<span class="h4"><a class="selflink" id="section-6.3.3" href="#section-6.3.3">6.3.3</a>.  certificate-values Attribute Definition</span>

   This attribute may be used to contain the certificate information
   required for the following forms of extended electronic signature:
   CAdES-X Long, ES X-Long Type 1, and CAdES-X Long Type 2; see Annex
   B.1.1 for an illustration of this form of electronic signature.

   The certificate-values attribute is an unsigned attribute.  Only a
   single instance of this attribute shall occur with an electronic
   signature.  It holds the values of certificates referenced in the
   complete-certificate-references attribute.

      NOTE: If an attribute certificate is used, it is not provided in
      this structure but shall be provided by the signer as a
      signer-attributes attribute (see <a href="#section-5.11.3">Section 5.11.3</a>).

   The following object identifier identifies the certificate-values
   attribute:

   id-aa-ets-certValues OBJECT IDENTIFIER ::= { iso(1) member-body(2)
   us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 23}

   The certificate-values attribute value has the ASN.1 syntax
   CertificateValues.

   CertificateValues ::=  SEQUENCE OF Certificate

   Certificate is defined in <a href="#section-7.1">Section 7.1</a>. (which is as defined in ITU-T
   Recommendation X.509 [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>]).

   This attribute may include the certification information for any TSUs
   that have provided the time-stamp tokens, if these certificates are
   not already included in the TSTs as part of the TSUs signatures.  In
   this case, the unsigned attribute shall be added to the signedData of
   the relevant time-stamp token.

<span class="h4"><a class="selflink" id="section-6.3.4" href="#section-6.3.4">6.3.4</a>.  revocation-values Attribute Definition</span>

   This attribute is used to contain the revocation information required
   for the following forms of extended electronic signature: CAdES-X
   Long, ES X-Long Type 1, and CAdES-X Long Type 2; see Annex B.1.1 for
   an illustration of this form of electronic signature.

   The revocation-values attribute is an unsigned attribute.  Only a
   single instance of this attribute shall occur with an electronic



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   signature.  It holds the values of CRLs and OCSP referenced in the
   complete-revocation-references attribute.

      NOTE: It is recommended that this attribute be used in preference
      to the OtherRevocationInfoFormat specified in <a href="./rfc3852">RFC 3852</a> to maintain
      backwards compatibility with the earlier version of this
      specification.

   The following object identifier identifies the revocation-values
   attribute:

   id-aa-ets-revocationValues OBJECT IDENTIFIER ::= { iso(1)
   member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
   smime(16) id-aa(2) 24}

   The revocation-values attribute value has the ASN.1 syntax
   RevocationValues

   RevocationValues ::=  SEQUENCE {
      crlVals          [0] SEQUENCE OF CertificateList OPTIONAL,
      ocspVals         [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>] SEQUENCE OF BasicOCSPResponse OPTIONAL,
      otherRevVals     [<a href="#ref-2" title="&quot;Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile&quot;">2</a>] OtherRevVals OPTIONAL }

   OtherRevVals ::= SEQUENCE {
      OtherRevValType   OtherRevValType,
      OtherRevVals      ANY DEFINED BY OtherRevValType }

   OtherRevValType ::= OBJECT IDENTIFIER

   The syntax and semantics of the other revocation values
   (OtherRevVals) are outside the scope of the present document.

   The definition of the syntax of the other form of revocation
   information is as identified by OtherRevRefType.

   CertificateList is defined in <a href="#section-7.2">Section 7.2</a>. (which is as defined in
   ITU-T Recommendation X.509 [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>]).

   BasicOCSPResponse is defined in <a href="#section-7.3">Section 7.3</a>. (which is as defined in
   <a href="./rfc2560">RFC 2560</a> [<a href="#ref-3" title="&quot;X.509 Internet Public Key Infrastructure Online Certificate Status Protocol - OCSP&quot;">3</a>]).

   This attribute may include the values of revocation data including
   CRLs and OCSPs for any TSUs that have provided the time-stamp tokens,
   if these certificates are not already included in the TSTs as part of
   the TSUs signatures.  In this case, the unsigned attribute shall be
   added to the signedData of the relevant time-stamp token.





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<span class="h4"><a class="selflink" id="section-6.3.5" href="#section-6.3.5">6.3.5</a>.  CAdES-C-time-stamp Attribute Definition</span>

   This attribute is used to protect against CA key compromise.

   This attribute is used for the time-stamping of the complete
   electronic signature (CAdES-C).  It is used in the following forms of
   extended electronic signature; CAdES-X Type 1 and CAdES-X Long Type
   1; see Annex B.1.2 for an illustration of this form of electronic
   signature.

   The CAdES-C-time-stamp attribute is an unsigned attribute.  It is a
   time-stamp token of the hash of the electronic signature and the
   complete validation data (CAdES-C).  It is a special-purpose
   TimeStampToken Attribute that time-stamps the CAdES-C.  Several
   instances of this attribute may occur with an electronic signature
   from different TSAs.

      NOTE 1: It is recommended that the attributes being time-stamped
      be encoded in DER.  If DER is not employed, then the binary
      encoding of the ASN.1 structures being time-stamped should be
      preserved to ensure that the recalculation of the data hash is
      consistent.

      NOTE 2: Each attribute is included in the hash with the attrType
      and attrValues (including type and length) but without the type
      and length of the outer SEQUENCE.

   The following object identifier identifies the CAdES-C-Timestamp
   attribute:

   id-aa-ets-escTimeStamp OBJECT IDENTIFIER ::= { iso(1) member-body(2)
   us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 25}

   The CAdES-C-timestamp attribute value has the ASN.1 syntax
   ESCTimeStampToken :

   ESCTimeStampToken ::= TimeStampToken

   The value of the messageImprint field within TimeStampToken shall be
   a hash of the concatenated values (without the type or length
   encoding for that value) of the following data objects:

      - OCTETSTRING of the SignatureValue field within SignerInfo;

      - signature-time-stamp, or a time-mark operated by a Time-Marking
        Authority;

      - complete-certificate-references attribute; and



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      - complete-revocation-references attribute.

   For further information and definition of the TimeStampToken, see
   <a href="#section-7.4">Section 7.4</a>.

<span class="h4"><a class="selflink" id="section-6.3.6" href="#section-6.3.6">6.3.6</a>.  time-stamped-certs-crls-references Attribute Definition</span>

   This attribute is used to protect against CA key compromise.  This
   attribute is used for the time-stamping certificate and revocation
   references.  It is used in the following forms of extended electronic
   signature: CAdES-X Type 2 and CAdES-X Long Type 2; see Annex B.1.3
   for an illustration of this form of electronic signature.

   A time-stamped-certs-crls-references attribute is an unsigned
   attribute.  It is a time-stamp token issued for a list of referenced
   certificates and OCSP responses and/or CRLs to protect against
   certain CA compromises.  Its syntax is as follows:

      NOTE 1: It is recommended that the attributes being time-stamped
      be encoded in DER.  If DER is not employed, then the binary
      encoding of the ASN.1 structures being time-stamped should be
      preserved to ensure that the recalculation of the data hash is
      consistent.

      NOTE 2: Each attribute is included in the hash with the attrType
      and attrValues (including type and length) but without the type
      and length of the outer SEQUENCE.

   The following object identifier identifies the
   time-stamped-certs-crls-references attribute:

   id-aa-ets-certCRLTimestamp OBJECT IDENTIFIER ::=
   { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
   smime(16) id-aa(2) 26}

   The attribute value has the ASN.1 syntax TimestampedCertsCRLs:

   TimestampedCertsCRLs ::= TimeStampToken

   The value of the messageImprint field within the TimeStampToken shall
   be a hash of the concatenated values (without the type or length
   encoding for that value) of the following data objects, as present in
   the ES with Complete validation data (CAdES-C):

      - complete-certificate-references attribute; and

      - complete-revocation-references attribute.




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<span class="h3"><a class="selflink" id="section-6.4" href="#section-6.4">6.4</a>.  Archive Validation Data</span>

   Where an electronic signature is required to last for a very long
   time, and the time-stamp token on an electronic signature is in
   danger of being invalidated due to algorithm weakness or limits in
   the validity period of the TSA certificate, it may be required to
   time-stamp the electronic signature several times.  When this is
   required, an archive time-stamp attribute may be required for the
   archive form of the electronic signature (CAdES-A).  This archive
   time-stamp attribute may be repeatedly applied over a period of time.

<span class="h4"><a class="selflink" id="section-6.4.1" href="#section-6.4.1">6.4.1</a>.  archive-time-stamp Attribute Definition</span>

   The archive-time-stamp attribute is a time-stamp token of many of the
   elements of the signedData in the electronic signature.  If the
   certificate-values and revocation-values attributes are not present
   in the CAdES-BES or CAdES-EPES, then they shall be added to the
   electronic signature prior to computing the archive time-stamp token.

   The archive-time-stamp attribute is an unsigned attribute.  Several
   instances of this attribute may occur with an electronic signature
   both over time and from different TSUs.

   The following object identifier identifies the nested
   archive-time-stamp attribute:

   id-aa-ets-archiveTimestampV2  OBJECT IDENTIFIER ::=
   { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
   smime(16) id-aa(2) 48}

   Archive-time-stamp attribute values have the ASN.1 syntax
   ArchiveTimeStampToken

   ArchiveTimeStampToken ::= TimeStampToken

   The value of the messageImprint field within TimeStampToken shall be
   a hash of the concatenation of:

      - the encapContentInfo element of the SignedData sequence;

      - any external content being protected by the signature, if the
        eContent element of the encapContentInfo is omitted;

      - the Certificates and crls elements of the SignedData sequence,
        when present, and;

      - all data elements in the SignerInfo sequence including all
        signed and unsigned attributes.



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      NOTE 1: An alternative archiveTimestamp attribute, identified by
      an object identifier { iso(1) member-body(2) us(840)
      rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 27, is defined
      in prior versions of TS 101 733 [<a href="#ref-TS101733">TS101733</a>] and in <a href="./rfc3126">RFC 3126</a>.

      The archiveTimestamp attribute, defined in versions of TS 101 733
      prior to 1.5.1 and in <a href="./rfc3126">RFC 3126</a>, is not compatible with the
      attribute defined in the current document.  The archiveTimestamp
      attribute, defined in versions 1.5.1 to 1.6.3 of TS 101 733, is
      compatible with the current document if the content is internal to
      encapContentInfo.  Unless the version of TS 101 733 employed by
      the signing party is known by all recipients, use of the
      archiveTimestamp attribute defined in prior versions of TS 101 733
      is deprecated.

      NOTE 2: Counter signatures held as countersignature attributes do
      not require independent archive time-stamps, as they are protected
      by the archive time-stamp against the containing SignedData
      structure.

      NOTE 3: Unless DER is used throughout, it is recommended that the
      binary encoding of the ASN.1 structures being time-stamped be
      preserved when being archived to ensure that the recalculation of
      the data hash is consistent.

      NOTE 4: The hash is calculated over the concatenated data elements
      as received/stored, including the Type and Length encoding.

      NOTE 5: Whilst it is recommended that unsigned attributes be DER
      encoded, it cannot generally be so guaranteed except by prior
      arrangement.  For further information and definition of
      TimeStampToken, see <a href="#section-7.4">Section 7.4</a>.  The timestamp should be created
      using stronger algorithms (or longer key lengths) than in the
      original electronic signatures and weak algorithm (key length)
      timestamps.

      NOTE 6: This form of ES also provides protection against a TSP key
      compromise.

   The ArchiveTimeStamp will be added as an unsigned attribute in the
   SignerInfo sequence.  For the validation of one ArchiveTimeStamp, the
   data elements of the SignerInfo must be concatenated, excluding all
   later ArchivTimeStampToken attributes.

   Certificates and revocation information required to validate the
   ArchiveTimeStamp shall be provided by one of the following methods:





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      - The TSU provides the information in the SignedData of the
        timestamp token;

      - Adding the complete-certificate-references attribute and the
        complete-revocation-references attribute of the TSP as an
        unsigned attribute within TimeStampToken, when the required
        information is stored elsewhere; or

      - Adding the certificate-values attribute and the
        revocation-values attribute of the TSP as an unsigned attribute
        within TimeStampToken, when the required information is stored
        elsewhere.

<span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a>.  Other Standard Data Structures</span>

<span class="h3"><a class="selflink" id="section-7.1" href="#section-7.1">7.1</a>.  Public Key Certificate Format</span>

   The X.509 v3 certificate basis syntax is defined in ITU-T
   Recommendation X.509 [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>].  A profile of the X.509 v3 certificate is
   defined in <a href="./rfc3280">RFC 3280</a> [<a href="#ref-2" title="&quot;Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile&quot;">2</a>].

<span class="h3"><a class="selflink" id="section-7.2" href="#section-7.2">7.2</a>.  Certificate Revocation List Format</span>

   The X.509 v2 CRL syntax is defined in ITU-T Recommendation X.509 [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>].
   A profile of the X.509 v2 CRL is defined in <a href="./rfc3280">RFC 3280</a> [<a href="#ref-2" title="&quot;Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile&quot;">2</a>].

<span class="h3"><a class="selflink" id="section-7.3" href="#section-7.3">7.3</a>.  OCSP Response Format</span>

   The format of an OCSP token is defined in <a href="./rfc2560">RFC 2560</a> [<a href="#ref-3" title="&quot;X.509 Internet Public Key Infrastructure Online Certificate Status Protocol - OCSP&quot;">3</a>].

<span class="h3"><a class="selflink" id="section-7.4" href="#section-7.4">7.4</a>.  Time-Stamp Token Format</span>

   The format of a TimeStampToken type is defined in <a href="./rfc3161">RFC 3161</a> [<a href="#ref-7" title="&quot;Internet X.509 Public Key Infrastructure Time-Stamp Protocol (TSP)&quot;">7</a>] and
   profiled in ETSI TS 101 861 [<a href="#ref-TS101861" title="&quot;Time stamping profile&quot;">TS101861</a>].

<span class="h3"><a class="selflink" id="section-7.5" href="#section-7.5">7.5</a>.  Name and Attribute Formats</span>

   The syntax of the naming and other attributes is defined in ITU-T
   Recommendation X.509 [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>].

      NOTE: The name used by the signer, held as the subject in the
      signer's certificate, is allocated and verified on registration
      with the Certification Authority, either directly or indirectly
      through a Registration Authority, before being issued with a
      Certificate.






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   The present document places no restrictions on the form of the name.
   The subject's name may be a distinguished name, as defined in ITU-T
   Recommendation X.500 [<a href="#ref-12" title="&quot;Information technology - Open Systems Interconnection - The Directory: Overview of concepts, models and services&quot;">12</a>], held in the subject field of the
   certificate, or any other name form held in the subjectAltName
   certificate extension field, as defined in ITU-T Recommendation X.509
   [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>].  In the case that the subject has no distinguished name, the
   subject name can be an empty sequence and the subjectAltName
   extension shall be critical.

   All Certification Authorities, Attribute Authorities, and
   Time-Stamping Authorities shall use distinguished names in the
   subject field of their certificate.

   The distinguished name shall include identifiers for the organization
   providing the service and the legal jurisdiction (e.g., country)
   under which it operates.

   Where a signer signs as an individual, but wishes to also identify
   him/herself as acting on behalf of an organization, it may be
   necessary to provide two independent forms of identification.  The
   first identity, which is directly associated with the signing key,
   identifies him/her as an individual.  The second, which is managed
   independently, identifies that person acting as part of the
   organization, possibly with a given role.  In this case, one of the
   two identities is carried in the subject/subjectAltName field of the
   signer's certificate as described above.

   The present document does not specify the format of the signer's
   attribute that may be included in public key certificates.

      NOTE: The signer's attribute may be supported by using a claimed
      role in the CMS signed attributes field or by placing an attribute
      certificate containing a certified role in the CMS signed
      attributes field; see <a href="#section-7.6">Section 7.6</a>.

<span class="h3"><a class="selflink" id="section-7.6" href="#section-7.6">7.6</a>.  AttributeCertificate</span>

   The syntax of the AttributeCertificate type is defined in <a href="./rfc3281">RFC 3281</a>
   [<a href="#ref-13" title="&quot;An Internet Attribute Certificate Profile for Authorization&quot;">13</a>].

<span class="h2"><a class="selflink" id="section-8" href="#section-8">8</a>.  Conformance Requirements</span>

   For implementations supporting signature generation, the present
   document defines conformance requirements for the generation of two
   forms of basic electronic signature, one of the two forms must be
   implemented.





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<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


   For implementations supporting signature verification, the present
   document defines conformance requirements for the verification of two
   forms of basic electronic signature, one of the two forms must be
   implemented.

   The present document only defines conformance requirements up to an
   ES with Complete validation data (CAdES-C).  This means that none of
   the extended and archive forms of the electronic signature (CAdES-X,
   CAdES-A) need to be implemented to get conformance to the present
   document.

   On verification the inclusion of optional signed and unsigned
   attributes must be supported only to the extent that the signature is
   verifiable.  The semantics of optional attributes may be unsupported,
   unless specified otherwise by a signature policy.

<span class="h3"><a class="selflink" id="section-8.1" href="#section-8.1">8.1</a>.  CAdES-Basic Electronic Signature (CAdES-BES)</span>

   A system supporting CAdES-BES signers, according to the present
   document, shall, at a minimum, support generation of an electronic
   signature consisting of the following components:

      - The general CMS syntax and content type, as defined in <a href="./rfc3852">RFC 3852</a>
        [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>] (see Sections <a href="#section-5.1">5.1</a> and <a href="#section-5.2">5.2</a>);

      - CMS SignedData, as defined in <a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>], with the version set
        to 3 and at least one SignerInfo present (see Sections <a href="#section-5.3">5.3</a> to
        5.6);

         - The following CMS attributes, as defined in <a href="./rfc3852">RFC 3852</a> [<a href="#ref-4" title="&quot;Cryptographic Message Syntax (CMS)&quot;">4</a>]:

         - content-type; this shall always be present (see <a href="#section-5.7.1">Section</a>
           <a href="#section-5.7.1">5.7.1</a>); and

         - message-digest; this shall always be present (see <a href="#section-5.7.2">Section</a>
           <a href="#section-5.7.2">5.7.2</a>).

      - One of the following attributes, as defined in the present
        document:

         - signing-certificate: as defined in <a href="#section-5.7.3.1">Section 5.7.3.1</a>; or
         - signing-certificate v2 : as defined in <a href="#section-5.7.3.2">Section 5.7.3.2</a>.

      NOTE: <a href="./rfc3126">RFC 3126</a> was using the other signing-certificate attribute
      (see <a href="#section-5.7.3.3">Section 5.7.3.3</a>).  Its use is now deprecated, since the
      structure of the signing-certificate v2 attribute is simpler than
      the other signing-certificate attribute.




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<span class="h3"><a class="selflink" id="section-8.2" href="#section-8.2">8.2</a>.  CAdES-Explicit Policy-based Electronic Signature</span>

   A system supporting Policy-based signers, according to the present
   document, shall, at a minimum, support the generation of an
   electronic signature consisting of the previous components defined
   for the basic signer, plus:

      - The following attributes, as defined in <a href="#section-5.9">Section 5.9</a>:

         - signature-policy-identifier; this shall always be present
           (see <a href="#section-5.8.1">Section 5.8.1</a>).

<span class="h3"><a class="selflink" id="section-8.3" href="#section-8.3">8.3</a>.  Verification Using Time-Stamping</span>

   A system supporting verifiers, according to the present document,
   with time-stamping facilities shall, at a minimum, support:

      - verification of the mandated components of an electronic
        signature, as defined in <a href="#section-8.1">Section 8.1</a>;

      - signature-time-stamp attribute, as defined in <a href="#section-6.1.1">Section 6.1.1</a>;

      - complete-certificate-references attribute, as defined in <a href="#section-6.2.1">Section</a>
        <a href="#section-6.2.1">6.2.1</a>;

      - complete-revocation-references attribute, as defined in <a href="#section-6.2.2">Section</a>
        <a href="#section-6.2.2">6.2.2</a>;

      - Public Key Certificates, as defined in ITU-T Recommendation
        X.509 [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>] (see <a href="#section-8.1">Section 8.1</a>); and

      - either of:

         - Certificate Revocation Lists, as defined in ITU-T
           Recommendation X.509 [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>] (see <a href="#section-8.2">Section 8.2</a>); or

         - Online Certificate Status Protocol, as defined in <a href="./rfc2560">RFC 2560</a>
           [<a href="#ref-3" title="&quot;X.509 Internet Public Key Infrastructure Online Certificate Status Protocol - OCSP&quot;">3</a>] (see <a href="#section-8.3">Section 8.3</a>).

<span class="h3"><a class="selflink" id="section-8.4" href="#section-8.4">8.4</a>.  Verification Using Secure Records</span>

   A system supporting verifiers, according to the present document,
   shall, at a minimum, support:

      - verification of the mandated components of an electronic
        signature, as defined in <a href="#section-8.1">Section 8.1</a>;





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      - complete-certificate-references attribute, as defined in <a href="#section-6.2.1">Section</a>
        <a href="#section-6.2.1">6.2.1</a>;

      - complete-revocation-references attribute, as defined in <a href="#section-6.2.2">Section</a>
        <a href="#section-6.2.2">6.2.2</a>;

      - a record of the electronic signature and the time when the
        signature was first validated, using the referenced certificates
        and revocation information, must be maintained, such that
        records cannot be undetectably modified;

      - Public Key Certificates, as defined in ITU-T Recommendation
        X.509 [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>] (see <a href="#section-8.1">Section 8.1</a>); and

         - either of:

            - Certificate Revocation Lists, as defined in ITU-T
              Recommendation X.509 [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>] (see <a href="#section-8.2">Section 8.2</a>); or

            - online Certificate Status Protocol, as defined in <a href="./rfc2560">RFC 2560</a>
              [<a href="#ref-3" title="&quot;X.509 Internet Public Key Infrastructure Online Certificate Status Protocol - OCSP&quot;">3</a>] (see <a href="#section-8.3">Section 8.3</a>).

<span class="h2"><a class="selflink" id="section-9" href="#section-9">9</a>.  References</span>

<span class="h3"><a class="selflink" id="section-9.1" href="#section-9.1">9.1</a>.  Normative References</span>

   [<a id="ref-1">1</a>]    ITU-T Recommendation X.509 (2000)/ISO/IEC 9594-8 (2001):
          "Information technology - Open Systems Interconnection - The
          Directory: Public key and Attribute Certificate framework".

   [<a id="ref-2">2</a>]    Housley, R., Polk, W., Ford, W., and D. Solo, "Internet X.509
          Public Key Infrastructure Certificate and Certificate
          Revocation List (CRL) Profile", <a href="./rfc3280">RFC 3280</a>, April 2002.

   [<a id="ref-3">3</a>]    Myers, M., Ankney, R., Malpani, A., Galperin, S., and C.
          Adams, "X.509 Internet Public Key Infrastructure Online
          Certificate Status Protocol - OCSP", <a href="./rfc2560">RFC 2560</a>, June 1999.

   [<a id="ref-4">4</a>]    Housley, R., "Cryptographic Message Syntax (CMS)", <a href="./rfc3852">RFC 3852</a>,
          July 2004.

   [<a id="ref-5">5</a>]    Hoffman, P., Ed., "Enhanced Security Services for S/MIME", <a href="./rfc2634">RFC</a>
          <a href="./rfc2634">2634</a>, June 1999.

   [<a id="ref-6">6</a>]    Freed, N. and N. Borenstein, "Multipurpose Internet Mail
          Extensions (MIME) Part One: Format of Internet Message
          Bodies", <a href="./rfc2045">RFC 2045</a>, November 1996.




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   [<a id="ref-7">7</a>]    Adams, C., Cain, P., Pinkas, D., and R. Zuccherato, "Internet
          X.509 Public Key Infrastructure Time-Stamp Protocol (TSP)",
          <a href="./rfc3161">RFC 3161</a>, August 2001.

   [<a id="ref-8">8</a>]    ITU-T Recommendation X.680 (1997): "Information technology -
          Abstract Syntax Notation One (ASN.1): Specification of basic
          notation".

   [<a id="ref-9">9</a>]    ITU-T Recommendation X.501 (2000)/ISO/IEC 9594-1 (2001):
          "Information technology - Open Systems Interconnection -
          Directory models".

   [<a id="ref-10">10</a>]   Housley, R., "Cryptographic Message Syntax (CMS) Algorithms",
          <a href="./rfc3370">RFC 3370</a>, August 2002.

   [<a id="ref-11">11</a>]   ITU-T Recommendation F.1: "Operational provisions for the
          international public telegram service".

   [<a id="ref-12">12</a>]   ITU-T Recommendation X.500: "Information technology - Open
          Systems Interconnection - The Directory: Overview of concepts,
          models and services".

   [<a id="ref-13">13</a>]   Farrell, S. and R. Housley, "An Internet Attribute Certificate
          Profile for Authorization", <a href="./rfc3281">RFC 3281</a>, April 2002.

   [<a id="ref-14">14</a>]   ITU-T Recommendation X.208 (1988): "Specification of Abstract
          Syntax Notation One (ASN.1)".

   [<a id="ref-15">15</a>]   Schaad, J., "Enhanced Security Services (ESS) Update: Adding
          CertID Algorithm Agility", <a href="./rfc5035">RFC 5035</a>, August 2007.

   [<a id="ref-16">16</a>]   ITU-T Recommendation X.690 (2002): "Information technology
          ASN.1 encoding rules: Specification of Basic Encoding Rules
          (BER), Canonical Encoding Rules (CER) and Distinguished
          Encoding Rules (DER)".

<span class="h3"><a class="selflink" id="section-9.2" href="#section-9.2">9.2</a>.  Informative References</span>

   [<a id="ref-EUDirective">EUDirective</a>]  Directive 1999/93/EC of the European Parliament and of
                  the Council of 13 December 1999 on a community
                  framework for Electronic Signatures.

   [<a id="ref-TS101733">TS101733</a>]     ETSI Standard TS 101 733 V.1.7.3 (2005-06) Electronic
                  Signature Formats.

   [<a id="ref-TS101861">TS101861</a>]     ETSI TS 101 861: "Time stamping profile".





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<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


   [<a id="ref-TS101903">TS101903</a>]     ETSI TS 101 903: "XML Advanced Electronic Signatures
                  (XAdES)".

   [<a id="ref-TR102038">TR102038</a>]     ETSI TR 102 038: "Electronic Signatures and
                  Infrastructures (ESI); XML format for signature
                  policies".

   [<a id="ref-TR102272">TR102272</a>]     ETSI TR 102 272 V1.1.1 (2003-12). "Electronic
                  Signatures and Infrastructures (ESI); ASN.1 format for
                  signature policies".

   [<a id="ref-RFC2479">RFC2479</a>]      Adams, C., "Independent Data Unit Protection Generic
                  Security Service Application Program Interface (IDUP-
                  GSS-API)", <a href="./rfc2479">RFC 2479</a>, December 1998.

   [<a id="ref-RFC2743">RFC2743</a>]      Linn, J., "Generic Security Service Application
                  Program Interface Version 2, Update 1", <a href="./rfc2743">RFC 2743</a>,
                  January 2000.

   [<a id="ref-RFC3125">RFC3125</a>]      Ross, J., Pinkas, D., and N. Pope, "Electronic
                  Signature Policies", <a href="./rfc3125">RFC 3125</a>, September 2001.

   [<a id="ref-RFC3447">RFC3447</a>]      Jonsson, J. and B. Kaliski, "Public-Key Cryptography
                  Standards (PKCS) #1: RSA Cryptography Specifications
                  Version 2.1", <a href="./rfc3447">RFC 3447</a>, February 2003.

   [<a id="ref-RFC3494">RFC3494</a>]      Zeilenga, K., "Lightweight Directory Access Protocol
                  version 2 (LDAPv2) to Historic Status", <a href="./rfc3494">RFC 3494</a>,
                  March 2003.

   [<a id="ref-RFC3851">RFC3851</a>]      Ramsdell, B., Ed., "Secure/Multipurpose Internet Mail
                  Extensions (S/MIME) Version 3.1 Message
                  Specification", <a href="./rfc3851">RFC 3851</a>, July 2004.

   [<a id="ref-RFC4210">RFC4210</a>]      Adams, C., Farrell, S., Kause, T., and T. Mononen,
                  "Internet X.509 Public Key Infrastructure Certificate
                  Management Protocol (CMP)", <a href="./rfc4210">RFC 4210</a>, September 2005.

   [<a id="ref-RFC4346">RFC4346</a>]      Dierks, T. and E. Rescorla, "The Transport Layer
                  Security (TLS) Protocol Version 1.1", <a href="./rfc4346">RFC 4346</a>, April
                  2006.

   [<a id="ref-RFC4523">RFC4523</a>]      Zeilenga, K., "Lightweight Directory Access Protocol
                  (LDAP) Schema Definitions for X.509 Certificates", <a href="./rfc4523">RFC</a>
                  <a href="./rfc4523">4523</a>, June 2006.






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   [<a id="ref-ISO7498-2">ISO7498-2</a>]    ISO 7498-2 (1989): "Information processing systems -
                  Open Systems Interconnection - Basic Reference Model -
                  Part 2: Security Architecture".

   [<a id="ref-ISO9796-2">ISO9796-2</a>]    ISO/IEC 9796-2 (2002): "Information technology -
                  Security techniques - Digital signature schemes giving
                  message recovery - Part 2: Integer factorization based
                  mechanisms".

   [<a id="ref-ISO9796-4">ISO9796-4</a>]    ISO/IEC 9796-4 (1998): "Digital signature schemes
                  giving message recovery - Part 4: Discrete logarithm
                  based mechanisms".

   [<a id="ref-ISO10118-1">ISO10118-1</a>]   ISO/IEC 10118-1 (2000): "Information technology -
                  Security techniques - Hash-functions - Part 1:
                  General".

   [<a id="ref-ISO10118-2">ISO10118-2</a>]   ISO/IEC 10118-2 (2000): "Information technology -
                  Security techniques - Hash-functions - Part 2:
                  Hash-functions using an n-bit block cipher algorithm".

   [<a id="ref-ISO10118-3">ISO10118-3</a>]   ISO/IEC 10118-3 (2004): "Information technology -
                  Security techniques - Hash-functions - Part 3:
                  Dedicated hash-functions".

   [<a id="ref-ISO10118-4">ISO10118-4</a>]   ISO/IEC 10118-4 (1998): "Information technology -
                  Security techniques - Hash-functions - Part 4: Hash-
                  functions using modular arithmetic".

   [<a id="ref-ISO10181-5">ISO10181-5</a>]   ISO/IEC 10181-5:  Security Frameworks in Open Systems.
                  Non-Repudiation Framework.  April 1997.

   [<a id="ref-ISO13888-1">ISO13888-1</a>]   ISO/IEC 13888-1 (2004): "IT security techniques -
                  Non-repudiation - Part 1: General".

   [<a id="ref-ISO14888-1">ISO14888-1</a>]   ISO/IEC 14888-1 (1998): "Information technology -
                  Security techniques - Digital signatures with appendix
                  - Part 1: General".

   [<a id="ref-ISO14888-2">ISO14888-2</a>]   ISO/IEC 14888-2 (1999): "Information technology -
                  Security techniques - Digital signatures with appendix
                  - Part 2: Identity-based mechanisms".

   [<a id="ref-ISO14888-3">ISO14888-3</a>]   ISO/IEC 14888-3 (1998): "Information technology -
                  Security techniques - Digital signatures with appendix
                  - Part 3: Certificate-based mechanisms".





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   [<a id="ref-ISO15946-2">ISO15946-2</a>]   ISO/IEC 15946-2 (2002): "Information technology -
                  Security techniques - Cryptographic techniques based
                  on elliptic curves - Part 2: Digital signatures".

   [<a id="ref-CWA14171">CWA14171</a>]     CWA 14171 CEN Workshop Agreement: "General Guidelines
                  for Electronic Signature Verification".

   [<a id="ref-XMLDSIG">XMLDSIG</a>]      XMLDSIG: W3C/IETF Recommendation (February 2002):
                  "XML-Signature Syntax and Processing".

   [<a id="ref-X9.30-1">X9.30-1</a>]      ANSI X9.30-1 (1997): "Public Key Cryptography for the
                  Financial Services Industry - Part 1: The Digital
                  Signature Algorithm (DSA)".

   [<a id="ref-X9.30-2">X9.30-2</a>]      ANSI X9.30-2 (1997): "Public Key Cryptography for the
                  Financial Services Industry - Part 2: The Secure Hash
                  Algorithm (SHA-1)".

   [<a id="ref-X9.31-1">X9.31-1</a>]      ANSI X9.31-1 (1997): "Public Key Cryptography Using
                  Reversible Algorithms for the Financial Services
                  Industry - Part 1: The RSA Signature Algorithm".

   [<a id="ref-X9.31-2">X9.31-2</a>]      ANSI X9.31-2 (1996): "Public Key Cryptography Using
                  Reversible Algorithms for the Financial Services
                  Industry - Part 2: Hash Algorithms".

   [<a id="ref-X9.62">X9.62</a>]        ANSI X9.62 (1998): "Public Key Cryptography for the
                  Financial Services Industry - The Elliptic Curve
                  Digital Signature Algorithm (ECDSA)".

   [<a id="ref-P1363">P1363</a>]        IEEE P1363 (2000): "Standard Specifications for
                  Public-Key Cryptography".

   ETSI technical specifications can be downloaded free of charge via
   the Services and Products Download Area at:
   <a href="http://www.etsi.org/WebSite/Standards/StandardsDownload.aspx">http://www.etsi.org/WebSite/Standards/StandardsDownload.aspx</a>















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Annex A (Normative): ASN.1 Definitions

   This annex provides a summary of all the ASN.1 syntax definitions for
   new syntax defined in the present document.

<span class="h3"><a class="selflink" id="appendix-A.1" href="#appendix-A.1">A.1</a>.  Signature Format Definitions Using X.208 ASN.1 Syntax</span>

      NOTE: The ASN.1 module defined in Annex A.1 using syntax defined
      in ITU-T Recommendation X.208 [<a href="#ref-14" title="&quot;Specification of Abstract Syntax Notation One (ASN.1)&quot;">14</a>] has precedence over that
      defined in Annex A.2 in the case of any conflict.

ETS-ElectronicSignatureFormats-ExplicitSyntax88 { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-mod(0)
eSignature-explicit88(28)}

DEFINITIONS EXPLICIT TAGS ::=

BEGIN

-- EXPORTS All

IMPORTS

-- Cryptographic Message Syntax (CMS): <a href="./rfc3852">RFC 3852</a>

   ContentInfo, ContentType, id-data, id-signedData, SignedData,
   EncapsulatedContentInfo, SignerInfo, id-contentType,
   id-messageDigest, MessageDigest, id-signingTime, SigningTime,
   id-countersignature, Countersignature
      FROM CryptographicMessageSyntax2004
      { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
      smime(16) modules(0) cms-2004(24) }

-- ESS Defined attributes: ESS Update
-- <a href="./rfc5035">RFC 5035</a> (Adding CertID Algorithm Agility)

   id-aa-signingCertificate, SigningCertificate, IssuerSerial,
   id-aa-contentReference, ContentReference, id-aa-contentIdentifier,
   ContentIdentifier, id-aa-signingCertificateV2
      FROM ExtendedSecurityServices-2006
        { iso(1) member-body(2) us(840) rsadsi(113549)
          pkcs(1) pkcs-9(9) smime(16) modules(0) id-mod-ess-2006(30) }

-- Internet X.509 Public Key Infrastructure - Certificate and CRL
-- Profile: <a href="./rfc3280">RFC 3280</a>

   Certificate, AlgorithmIdentifier, CertificateList, Name,
   DirectoryString, Attribute, BMPString, UTF8String



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      FROM PKIX1Explicit88
      {iso(1) identified-organization(3) dod(6) internet(1)
      security(5) mechanisms(5) pkix(7) id-mod(0) id-pkix1-explicit(18)}

   GeneralNames, GeneralName, PolicyInformation
      FROM PKIX1Implicit88
      {iso(1) identified-organization(3) dod(6) internet(1) security(5)
       mechanisms(5) pkix(7) id-mod(0) id-pkix1-implicit (19)}

-- Internet Attribute Certificate Profile for Authorization - <a href="./rfc3281">RFC 3281</a>

   AttributeCertificate
      FROM PKIXAttributeCertificate {iso(1) identified-organization(3)
                dod(6) internet(1) security(5) mechanisms(5) pkix(7)
                id-mod(0) id-mod-attribute-cert(12)}

-- OCSP - <a href="./rfc2560">RFC 2560</a>

   BasicOCSPResponse, ResponderID
      FROM OCSP {iso(1) identified-organization(3) dod(6) internet(1)
      security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-ocsp(14)}

-- Time Stamp Protocol <a href="./rfc3161">RFC 3161</a>

   TimeStampToken
      FROM PKIXTSP
      {iso(1) identified-organization(3) dod(6) internet(1) security(5)
      mechanisms(5) pkix(7) id-mod(0) id-mod-tsp(13)}

;


-- Definitions of Object Identifier arcs used in the present document
-- ==================================================================

-- OID used referencing electronic signature mechanisms based on
-- the present document for use with the Independent Data Unit
-- Protection (IDUP) API (see Annex D)

   id-etsi-es-IDUP-Mechanism-v1 OBJECT IDENTIFIER ::=
   { itu-t(0) identified-organization(4) etsi(0)
     electronic-signature-standard (1733) part1 (1) idupMechanism (4)
     etsiESv1(1) }


-- Basic ES CMS Attributes Defined in the present document
-- =======================================================




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-- OtherSigningCertificate - deprecated

    id-aa-ets-otherSigCert OBJECT IDENTIFIER ::=
    { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
    smime(16) id-aa(2) 19 }

   OtherSigningCertificate ::=  SEQUENCE {
      certs        SEQUENCE OF OtherCertID,
      policies     SEQUENCE OF PolicyInformation OPTIONAL
                   -- NOT USED IN THE PRESENT DOCUMENT
   }

   OtherCertID ::= SEQUENCE {
      otherCertHash            OtherHash,
      issuerSerial             IssuerSerial OPTIONAL }

   OtherHash ::= CHOICE {
       sha1Hash     OtherHashValue,
       -- This contains a SHA-1 hash
       otherHash    OtherHashAlgAndValue}


-- Policy ES Attributes Defined in the present document
-- ====================================================

-- Mandatory Basic Electronic Signature Attributes as above,
-- plus in addition.

-- Signature-policy-identifier attribute

   id-aa-ets-sigPolicyId OBJECT IDENTIFIER ::=
   { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
   smime(16) id-aa(2) 15 }

   SignaturePolicy ::= CHOICE {
      signaturePolicyId          SignaturePolicyId,
      signaturePolicyImplied     SignaturePolicyImplied
                                 --  not used in this version
   }

   SignaturePolicyId ::= SEQUENCE {
      sigPolicyId        SigPolicyId,
      sigPolicyHash      SigPolicyHash,
      sigPolicyQualifiers   SEQUENCE SIZE (1..MAX) OF
                                   SigPolicyQualifierInfo OPTIONAL
   }

   SignaturePolicyImplied ::= NULL



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   SigPolicyId ::= OBJECT IDENTIFIER

   SigPolicyHash ::= OtherHashAlgAndValue

   OtherHashAlgAndValue ::= SEQUENCE {
      hashAlgorithm   AlgorithmIdentifier,
      hashValue       OtherHashValue }

   OtherHashValue ::= OCTET STRING

   SigPolicyQualifierInfo ::= SEQUENCE {
      sigPolicyQualifierId  SigPolicyQualifierId,
      sigQualifier          ANY DEFINED BY sigPolicyQualifierId }

   SigPolicyQualifierId ::=   OBJECT IDENTIFIER

   id-spq-ets-uri OBJECT IDENTIFIER ::=
   { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
   smime(16) id-spq(5) 1 }

   SPuri ::= IA5String

   id-spq-ets-unotice OBJECT IDENTIFIER ::=
   { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
   smime(16) id-spq(5) 2 }

   SPUserNotice ::= SEQUENCE {
       noticeRef        NoticeReference OPTIONAL,
       explicitText     DisplayText OPTIONAL}

   NoticeReference ::= SEQUENCE {
      organization     DisplayText,
      noticeNumbers    SEQUENCE OF INTEGER }

   DisplayText ::= CHOICE {
      visibleString    VisibleString  (SIZE (1..200)),
      bmpString        BMPString      (SIZE (1..200)),

      utf8String       UTF8String     (SIZE (1..200)) }

-- Optional Electronic Signature Attributes

-- Commitment-type attribute

id-aa-ets-commitmentType OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 16}

   CommitmentTypeIndication ::= SEQUENCE {



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     commitmentTypeId CommitmentTypeIdentifier,
     commitmentTypeQualifier SEQUENCE SIZE (1..MAX) OF
            CommitmentTypeQualifier OPTIONAL}

   CommitmentTypeIdentifier ::= OBJECT IDENTIFIER

   CommitmentTypeQualifier ::= SEQUENCE {
      commitmentTypeIdentifier CommitmentTypeIdentifier,
      qualifier   ANY DEFINED BY commitmentTypeIdentifier }

id-cti-ets-proofOfOrigin OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) cti(6) 1}

id-cti-ets-proofOfReceipt OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) cti(6) 2}

id-cti-ets-proofOfDelivery OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) cti(6) 3}

id-cti-ets-proofOfSender OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) cti(6) 4}

id-cti-ets-proofOfApproval OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) cti(6) 5}

id-cti-ets-proofOfCreation OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) cti(6) 6}

-- Signer-location attribute

id-aa-ets-signerLocation OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 17}

   SignerLocation ::= SEQUENCE {
       -- at least one of the following shall be present
       countryName    [0]   DirectoryString OPTIONAL,
          -- As used to name a Country in X.500
       localityName   [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>]   DirectoryString OPTIONAL,
           -- As used to name a locality in X.500
       postalAdddress [<a href="#ref-2" title="&quot;Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile&quot;">2</a>]   PostalAddress OPTIONAL }

   PostalAddress ::= SEQUENCE SIZE(1..6) OF DirectoryString

-- Signer-attributes attribute




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id-aa-ets-signerAttr OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 18}

   SignerAttribute ::= SEQUENCE OF CHOICE {
      claimedAttributes   [0] ClaimedAttributes,
      certifiedAttributes [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>] CertifiedAttributes }

   ClaimedAttributes ::= SEQUENCE OF Attribute

   CertifiedAttributes ::= AttributeCertificate
   -- as defined in <a href="./rfc3281">RFC 3281</a>: see <a href="#section-4.1">Section 4.1</a>

-- Content-time-stamp attribute

id-aa-ets-contentTimestamp OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 20}

   ContentTimestamp ::= TimeStampToken

-- Signature-time-stamp attribute

id-aa-signatureTimeStampToken OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 14}

SignatureTimeStampToken ::= TimeStampToken

-- Complete-certificate-references attribute

id-aa-ets-certificateRefs OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 21}

CompleteCertificateRefs ::=  SEQUENCE OF OtherCertID

-- Complete-revocation-references attribute

id-aa-ets-revocationRefs OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 22}

   CompleteRevocationRefs ::=  SEQUENCE OF CrlOcspRef

   CrlOcspRef ::= SEQUENCE {
      crlids          [0] CRLListID   OPTIONAL,
      ocspids         [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>] OcspListID  OPTIONAL,
      otherRev        [<a href="#ref-2" title="&quot;Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile&quot;">2</a>] OtherRevRefs OPTIONAL
   }




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   CRLListID ::=  SEQUENCE {
      crls        SEQUENCE OF CrlValidatedID}

   CrlValidatedID ::=  SEQUENCE {
      crlHash                   OtherHash,
      crlIdentifier             CrlIdentifier OPTIONAL}

   CrlIdentifier ::= SEQUENCE {
      crlissuer                 Name,
      crlIssuedTime             UTCTime,
      crlNumber                 INTEGER OPTIONAL }

   OcspListID ::=  SEQUENCE {
       ocspResponses        SEQUENCE OF OcspResponsesID}

   OcspResponsesID ::=  SEQUENCE {
       ocspIdentifier              OcspIdentifier,
       ocspRepHash                 OtherHash    OPTIONAL
   }

   OcspIdentifier ::= SEQUENCE {
      ocspResponderID      ResponderID,
      -- As in OCSP response data
      producedAt           GeneralizedTime
      -- As in OCSP response data
   }

   OtherRevRefs ::= SEQUENCE {
       otherRevRefType   OtherRevRefType,
       otherRevRefs      ANY DEFINED BY otherRevRefType
    }

   OtherRevRefType ::= OBJECT IDENTIFIER

-- Certificate-values attribute

id-aa-ets-certValues OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 23}

   CertificateValues ::=  SEQUENCE OF Certificate

-- Certificate-revocation-values attribute

id-aa-ets-revocationValues OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 24}

   RevocationValues ::=  SEQUENCE {



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      crlVals           [0] SEQUENCE OF CertificateList OPTIONAL,
      ocspVals          [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>] SEQUENCE OF BasicOCSPResponse OPTIONAL,
      otherRevVals      [<a href="#ref-2" title="&quot;Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile&quot;">2</a>] OtherRevVals OPTIONAL}

   OtherRevVals ::= SEQUENCE {
       otherRevValType   OtherRevValType,
       otherRevVals      ANY DEFINED BY otherRevValType
   }

   OtherRevValType ::= OBJECT IDENTIFIER

-- CAdES-C time-stamp attribute

id-aa-ets-escTimeStamp OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 25}

ESCTimeStampToken ::= TimeStampToken

-- Time-Stamped Certificates and CRLs

id-aa-ets-certCRLTimestamp OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 26}

TimestampedCertsCRLs ::= TimeStampToken

-- Archive time-stamp attribute
id-aa-ets-archiveTimestampV2  OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 48}

ArchiveTimeStampToken ::= TimeStampToken

-- Attribute-certificate-references attribute

id-aa-ets-attrCertificateRefs OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 44}

AttributeCertificateRefs ::=  SEQUENCE OF OtherCertID

-- Attribute-revocation-references attribute

id-aa-ets-attrRevocationRefs OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 45}

AttributeRevocationRefs ::=  SEQUENCE OF CrlOcspRef



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END

<span class="h3"><a class="selflink" id="appendix-A.2" href="#appendix-A.2">A.2</a>.  Signature Format Definitions Using X.680 ASN.1 Syntax</span>

      NOTE: The ASN.1 module defined in Annex A.1 has precedence over
      that defined in Annex A.2 using syntax defined in ITU-T
      Recommendation X.680 (1997) [<a href="#ref-8" title="&quot;Information technology - Abstract Syntax Notation One (ASN.1): Specification of basic notation&quot;">8</a>] in the case of any conflict.

ETS-ElectronicSignatureFormats-ExplicitSyntax97 { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-mod(0)
eSignature-explicit97(29)}

DEFINITIONS EXPLICIT TAGS ::=

BEGIN

-- EXPORTS All -

IMPORTS

-- Cryptographic Message Syntax (CMS): <a href="./rfc3852">RFC 3852</a>

   ContentInfo, ContentType, id-data, id-signedData, SignedData,
   EncapsulatedContentInfo, SignerInfo,
   id-contentType, id-messageDigest, MessageDigest, id-signingTime,
   SigningTime, id-countersignature, Countersignature
      FROM CryptographicMessageSyntax2004
      { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
       smime(16) modules(0) cms-2004(24) }

-- ESS Defined attributes: ESS Update
-- <a href="./rfc5035">RFC 5035</a> (Adding CertID Algorithm Agility)

   id-aa-signingCertificate, SigningCertificate, IssuerSerial,
   id-aa-contentReference, ContentReference, id-aa-contentIdentifier,
   ContentIdentifier, id-aa-signingCertificateV2
      FROM ExtendedSecurityServices-2006
        { iso(1) member-body(2) us(840) rsadsi(113549)
          pkcs(1) pkcs-9(9) smime(16) modules(0) id-mod-ess-2006(30) }

-- Internet X.509 Public Key Infrastructure
-- Certificate and CRL Profile: <a href="./rfc3280">RFC 3280</a>

   Certificate, AlgorithmIdentifier, CertificateList, Name,
   Attribute

      FROM PKIX1Explicit88
      {iso(1) identified-organization(3) dod(6) internet(1)



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      security(5) mechanisms(5) pkix(7) id-mod(0)
      id-pkix1-explicit(18)}

   GeneralNames, GeneralName, PolicyInformation
      FROM PKIX1Implicit88 {iso(1) identified-organization(3) dod(6)
      internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
      id-pkix1-implicit(19)}

-- Internet Attribute Certificate Profile for Authorization - <a href="./rfc3281">RFC 3281</a>

   AttributeCertificate
      FROM PKIXAttributeCertificate {iso(1) identified-organization(3)
      dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
      id-mod-attribute-cert(12)}

-- OCSP <a href="./rfc2560">RFC 2560</a>

   BasicOCSPResponse, ResponderID
      FROM OCSP {iso(1) identified-organization(3) dod(6) internet(1)
      security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-ocsp(14)}

-- <a href="./rfc3161">RFC 3161</a> Internet X.509 Public Key Infrastructure
-- Time-Stamp Protocol

   TimeStampToken
      FROM PKIXTSP {iso(1) identified-organization(3) dod(6) internet(1)
      security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-tsp(13)}

-- X.520

    DirectoryString {}
        FROM SelectedAttributeTypes
         {joint-iso-itu-t ds(5) module(1) selectedAttributeTypes(5) 4}

;

-- Definitions of Object Identifier arcs used in the present document
-- ==================================================================

-- OID used referencing electronic signature mechanisms based
-- on the present document for use with the IDUP API (see Annex D)

id-etsi-es-IDUP-Mechanism-v1 OBJECT IDENTIFIER ::=
{ itu-t(0) identified-organization(4) etsi(0)
electronic-signature-standard (1733) part1 (1) idupMechanism (4)
etsiESv1(1) }





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-- Basic ES Attributes Defined in the present document
-- ===================================================

-- CMS Attributes defined in the present document

-- OtherSigningCertificate - deprecated

id-aa-ets-otherSigCert OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-aa(2) 19 }


   OtherSigningCertificate ::=  SEQUENCE {
      certs        SEQUENCE OF OtherCertID,
      policies     SEQUENCE OF PolicyInformation OPTIONAL
                   -- NOT USED IN THE PRESENT DOCUMENT
   }

   OtherCertID ::= SEQUENCE {
      otherCertHash            OtherHash,
      issuerSerial             IssuerSerial OPTIONAL }

   OtherHash ::= CHOICE {
      sha1Hash OtherHashValue,
      -- This contains a SHA-1 hash
      otherHash OtherHashAlgAndValue}

-- Policy ES Attributes Defined in the present document
-- ====================================================

-- Mandatory Basic Electronic Signature Attributes, plus in addition.
-- Signature Policy Identifier

id-aa-ets-sigPolicyId OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-aa(2) 15 }

   SignaturePolicy ::= CHOICE {
      signaturePolicyId          SignaturePolicyId,
      signaturePolicyImplied     SignaturePolicyImplied
                              -- not used in this version
   }

   SignaturePolicyId ::= SEQUENCE {
      sigPolicyId           SigPolicyId,
      sigPolicyHash         SigPolicyHash,
      sigPolicyQualifiers   SEQUENCE SIZE (1..MAX) OF
                                 SigPolicyQualifierInfo OPTIONAL



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   }

   SignaturePolicyImplied ::= NULL

   SigPolicyId ::= OBJECT IDENTIFIER

   SigPolicyHash ::= OtherHashAlgAndValue

   OtherHashAlgAndValue ::= SEQUENCE {
      hashAlgorithm   AlgorithmIdentifier,
      hashValue       OtherHashValue
   }

   OtherHashValue ::= OCTET STRING

   SigPolicyQualifierInfo ::= SEQUENCE {
      sigPolicyQualifierId       SIG-POLICY-QUALIFIER.&amp;id
      ({SupportedSigPolicyQualifiers}),
      qualifier               SIG-POLICY-QUALIFIER.&amp;Qualifier
                                ({SupportedSigPolicyQualifiers}
                                    {@sigPolicyQualifierId})OPTIONAL }

   SupportedSigPolicyQualifiers SIG-POLICY-QUALIFIER ::=
       { noticeToUser | pointerToSigPolSpec }

   SIG-POLICY-QUALIFIER ::= CLASS {
      &amp;id             OBJECT IDENTIFIER UNIQUE,
      &amp;Qualifier      OPTIONAL }
   WITH SYNTAX {
      SIG-POLICY-QUALIFIER-ID     &amp;id
      [SIG-QUALIFIER-TYPE &amp;Qualifier] }

   noticeToUser SIG-POLICY-QUALIFIER ::= {
      SIG-POLICY-QUALIFIER-ID id-spq-ets-unotice SIG-QUALIFIER-TYPE
      SPUserNotice }

   pointerToSigPolSpec SIG-POLICY-QUALIFIER ::= {
      SIG-POLICY-QUALIFIER-ID id-spq-ets-uri SIG-QUALIFIER-TYPE SPuri }

   id-spq-ets-uri OBJECT IDENTIFIER ::= { iso(1)
    member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
    smime(16) id-spq(5) 1 }

   SPuri ::= IA5String

   id-spq-ets-unotice OBJECT IDENTIFIER ::= { iso(1)
   member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
   smime(16) id-spq(5) 2 }



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   SPUserNotice ::= SEQUENCE {
        noticeRef        NoticeReference OPTIONAL,
        explicitText     DisplayText OPTIONAL}

   NoticeReference ::= SEQUENCE {
        organization     DisplayText,
        noticeNumbers    SEQUENCE OF INTEGER }

   DisplayText ::= CHOICE {
        visibleString    VisibleString  (SIZE (1..200)),
        bmpString        BMPString      (SIZE (1..200)),
        utf8String       UTF8String     (SIZE (1..200)) }

-- Optional Electronic Signature Attributes

-- Commitment Type

  id-aa-ets-commitmentType OBJECT IDENTIFIER ::= { iso(1) member-body(2)
    us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 16}

   CommitmentTypeIndication ::= SEQUENCE {
      commitmentTypeId CommitmentTypeIdentifier,
      commitmentTypeQualifier SEQUENCE SIZE (1..MAX) OF
         CommitmentTypeQualifier OPTIONAL}

   CommitmentTypeIdentifier ::= OBJECT IDENTIFIER

   CommitmentTypeQualifier ::= SEQUENCE {
      commitmentQualifierId   COMMITMENT-QUALIFIER.&amp;id,
      qualifier               COMMITMENT-QUALIFIER.&amp;Qualifier OPTIONAL }

   COMMITMENT-QUALIFIER ::= CLASS {
      &amp;id             OBJECT IDENTIFIER UNIQUE,
      &amp;Qualifier      OPTIONAL }
   WITH SYNTAX {
      COMMITMENT-QUALIFIER-ID     &amp;id
      [COMMITMENT-TYPE &amp;Qualifier] }

id-cti-ets-proofOfOrigin OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) cti(6) 1}

id-cti-ets-proofOfReceipt OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) cti(6) 2}

id-cti-ets-proofOfDelivery OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
cti(6) 3}




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id-cti-ets-proofOfSender OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) cti(6) 4}

id-cti-ets-proofOfApproval OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) cti(6) 5}

id-cti-ets-proofOfCreation OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) cti(6) 6}

-- Signer Location

id-aa-ets-signerLocation OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 17}

   SignerLocation ::= SEQUENCE {
   -- at least one of the following shall be present
      countryName [0] DirectoryString{maxSize} OPTIONAL,
         -- as used to name a Country in X.520
      localityName [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>] DirectoryString{maxSize} OPTIONAL,
         -- as used to name a locality in X.520
      postalAdddress [<a href="#ref-2" title="&quot;Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile&quot;">2</a>] PostalAddress OPTIONAL }

   PostalAddress ::= SEQUENCE SIZE(1..6) OF DirectoryString{maxSize}
                    -- maxSize parametrization as specified in X.683

-- Signer Attributes

id-aa-ets-signerAttr OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 18}

   SignerAttribute ::= SEQUENCE OF CHOICE {
      claimedAttributes   [0] ClaimedAttributes,
      certifiedAttributes [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>] CertifiedAttributes }

   ClaimedAttributes ::= SEQUENCE OF Attribute

   CertifiedAttributes ::= AttributeCertificate
   -- as defined in <a href="./rfc3281">RFC 3281</a>: see <a href="#section-4.1">Section 4.1</a>

-- Content Timestamp

id-aa-ets-contentTimestamp OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 20}
   ContentTimestamp ::= TimeStampToken




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-- Signature Timestamp

id-aa-signatureTimeStampToken OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 14}

   SignatureTimeStampToken ::= TimeStampToken

-- Complete Certificate Refs.

id-aa-ets-certificateRefs OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 21}

CompleteCertificateRefs ::=  SEQUENCE OF OtherCertID

-- Complete Revocation Refs

id-aa-ets-revocationRefs OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 22}

   CompleteRevocationRefs ::=  SEQUENCE OF CrlOcspRef

   CrlOcspRef ::= SEQUENCE {
      crlids          [0] CRLListID   OPTIONAL,
      ocspids         [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>] OcspListID  OPTIONAL,
      otherRev        [<a href="#ref-2" title="&quot;Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile&quot;">2</a>] OtherRevRefs OPTIONAL
   }

   CRLListID ::=  SEQUENCE {
      crls        SEQUENCE OF CrlValidatedID
   }

   CrlValidatedID ::=  SEQUENCE {
      crlHash                   OtherHash,
      crlIdentifier             CrlIdentifier OPTIONAL   }

   CrlIdentifier ::= SEQUENCE {
       crlissuer                 Name,
       crlIssuedTime             UTCTime,
       crlNumber                 INTEGER OPTIONAL
   }

   OcspListID ::=  SEQUENCE {
       ocspResponses        SEQUENCE OF OcspResponsesID
   }

   OcspResponsesID ::=  SEQUENCE {
       ocspIdentifier              OcspIdentifier,



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       ocspRepHash                 OtherHash    OPTIONAL
   }

   OcspIdentifier ::= SEQUENCE {
      ocspResponderID      ResponderID,
      -- As in OCSP response data
      producedAt           GeneralizedTime
      -- As in OCSP response data
   }

   OtherRevRefs ::= SEQUENCE {
      otherRevRefType   OTHER-REVOCATION-REF.&amp;id,
      otherRevRefs      SEQUENCE OF OTHER-REVOCATION-REF.&amp;Type
   }

OTHER-REVOCATION-REF ::= CLASS {
      &amp;Type,
      &amp;id   OBJECT IDENTIFIER UNIQUE }
   WITH SYNTAX {
      WITH SYNTAX &amp;Type ID &amp;id }

-- Certificate Values

id-aa-ets-certValues OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 23}

CertificateValues ::=  SEQUENCE OF Certificate

-- Certificate Revocation Values

id-aa-ets-revocationValues OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 24}

   RevocationValues ::=  SEQUENCE {
     crlVals           [0] SEQUENCE OF CertificateList OPTIONAL,
     ocspVals          [<a href="#ref-1" title="&quot;Information technology - Open Systems Interconnection - The Directory: Public key and Attribute Certificate framework&quot;">1</a>] SEQUENCE OF BasicOCSPResponse OPTIONAL,

     otherRevVals      [<a href="#ref-2" title="&quot;Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile&quot;">2</a>] OtherRevVals OPTIONAL
   }

   OtherRevVals ::= SEQUENCE {
      otherRevValType   OTHER-REVOCATION-VAL.&amp;id,
      otherRevVals      SEQUENCE OF OTHER-REVOCATION-REF.&amp;Type
   }

  OTHER-REVOCATION-VAL ::= CLASS {
      &amp;Type,



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      &amp;id   OBJECT IDENTIFIER UNIQUE }
   WITH SYNTAX {
      WITH SYNTAX &amp;Type ID &amp;id }

-- CAdES-C Timestamp
id-aa-ets-escTimeStamp OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 25}

   ESCTimeStampToken ::= TimeStampToken

-- Time-Stamped Certificates and CRLs

id-aa-ets-certCRLTimestamp OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 26}

   TimestampedCertsCRLs ::= TimeStampToken

-- Archive Timestamp

id-aa-ets-archiveTimestampV2  OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 48}

   ArchiveTimeStampToken ::= TimeStampToken

-- Attribute certificate references

id-aa-ets-attrCertificateRefs OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 44}

   AttributeCertificateRefs ::=  SEQUENCE OF OtherCertID

-- Attribute revocation references

id-aa-ets-attrRevocationRefs OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 45}

   AttributeRevocationRefs ::=  SEQUENCE OF CrlOcspRef

END








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Annex B (Informative): Extended Forms of Electronic Signatures

   <a href="#section-4">Section 4</a> provides an overview of the various formats of electronic
   signatures included in the present document.  This annex lists the
   attributes that need to be present in the various extended electronic
   signature formats and provides example validation sequences using the
   extended formats.

<span class="h3"><a class="selflink" id="appendix-B.1" href="#appendix-B.1">B.1</a>.  Extended Forms of Validation Data</span>

   The Complete validation data (CAdES-C) described in <a href="#section-4.3">Section 4.3</a> and
   illustrated in Figure 3 may be extended to create electronic
   signatures with extended validation data.  Some electronic signature
   forms that include extended validation are explained below.

   An X-Long electronic signature (CAdES-X Long) is the CAdES-C with the
   values of the certificates and revocation information.

   This form of electronic signature can be useful when the verifier
   does not have direct access to the following information:

      - the signer's certificate;

      - all the CA certificates that make up the full certification
        path;

      - all the associated revocation status information, as referenced
        in the CAdES-C.

   In some situations, additional time-stamps may be created and added
   to the Electronic Signatures as additional attributes.  For example:

      - time-stamping all the validation data as held with the ES
        (CAdES-C), this eXtended validation data is called a CAdES-X
        Type 1; or

      - time-stamping individual reference data as used for complete
        validation.  This form of eXtended validation data is called an
        CAdES-X Type 2.

      NOTE 1: The advantages/drawbacks for CAdES-X Type 1 and CAdES-X
      Type 2 are discussed in Annex C.4.4.

   The above time-stamp forms can be useful when it is required to
   counter the risk that any CA keys used in the certificate chain may
   be compromised.





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   A combination of the two formats above may be used.  This form of
   eXtended validation data is called an ES X-Long Type 1 or CAdES-X
   Long Type 2.  This form of electronic signature can be useful when
   the verifier needs both the values and proof of when the validation
   data existed.

      NOTE 2: The advantages/drawbacks for CAdES-X long Type 1 and
      CAdES-X long Type 2 are discussed in Annex C.4.6.

<span class="h4"><a class="selflink" id="appendix-B.1.1" href="#appendix-B.1.1">B.1.1</a>.  CAdES-X Long</span>

   An electronic signature with the additional validation data forming
   the CAdES-X Long form (CAdES-X-Long) is illustrated in Figure B.1 and
   comprises the following:

      - CAdES-BES or CAdES-EPES, as defined in Sections <a href="#section-4.3">4.3</a> , 5.7, or
        5.8;

      - complete-certificate-references attribute, as defined in <a href="#section-6.2.1">Section</a>
        <a href="#section-6.2.1">6.2.1</a>;

      - complete-revocation-references attribute, as defined in <a href="#section-6.2.2">Section</a>
        <a href="#section-6.2.2">6.2.2</a>.

   The following attributes are required if a TSP is not providing a
   time-mark of the ES:

      - signature-time-stamp attribute, as defined in <a href="#section-6.1.1">Section 6.1.1</a>.

   The following attributes are required if the full certificate values
   and revocation values are not already included in the CAdES-BES or
   CAdES-EPES:

      - certificate-values attribute, as defined in <a href="#section-6.3.3">Section 6.3.3</a>;

      - revocation-values attribute, as defined in <a href="#section-6.3.4">Section 6.3.4</a>.

   If attributes certificates are used, then the following attributes
   may be present:

      - attribute-certificate-references attribute, defined in <a href="#section-6.2.3">Section</a>
        <a href="#section-6.2.3">6.2.3</a>;

      - attribute-revocation-references attribute, as defined in <a href="#section-6.2.4">Section</a>
        <a href="#section-6.2.4">6.2.4</a>.

   Other unsigned attributes may be present, but are not required.




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      NOTE: Attribute certificate and revocation references are only
      present if a user attribute certificate is present in the
      electronic signature; see Sections <a href="#section-6.2.2">6.2.2</a> and <a href="#section-6.2.3">6.2.3</a>.

+---------------------- CAdES-X-Long --------------------------------+
|+-------------------------------------- CAdES-C ---+                |
||                                     +----------+ | +-------------+|
||+----- CAdES-BES or CAdES-EPES ----+ |Timestamp | | |             ||
|||                                  | |over      | | | Complete    ||
|||+---------++----------++---------+| |digital   | | | certificate ||
||||         ||          ||         || |signature | | |    and      ||
||||Signer's ||  Signed  ||Digital  || |          | | | revocation  ||
||||Document ||Attributes||signature|| |Optional  | | |    data     ||
||||         ||          ||         || |when      | | |             ||
|||+---------++----------++---------+| |timemarked| | |             ||
||+----------------------------------+ +----------+ | |             ||
||                                     +-----------+| +-------------+|
||                                     |Complete   ||                |
||                                     |certificate||                |
||                                     |and        ||                |
||                                     |revocation ||                |
||                                     |references ||                |
||                                     +-----------+|                |
|+--------------------------------------------------+                |
|                                                                    |
+--------------------------------------------------------------------+

             Figure B.1: Illustration of CAdES-X-Long

<span class="h4"><a class="selflink" id="appendix-B.1.2" href="#appendix-B.1.2">B.1.2</a>.  CAdES-X Type 1</span>

   An electronic signature with the additional validation data forming
   the eXtended validation data - Type 1 X is illustrated in Figure B.2
   and comprises the following:

      - the CAdES-BES or CAdES-EPES, as defined in Sections <a href="#section-4.2">4.2</a>, <a href="#section-5.7">5.7</a>, or
        5.8;

      - complete-certificate-references attribute, as defined in <a href="#section-6.2.1">Section</a>
        <a href="#section-6.2.1">6.2.1</a>;

      - complete-revocation-references attribute, as defined in <a href="#section-6.2.2">Section</a>
        <a href="#section-6.2.2">6.2.2</a>;

      - CAdES-C-Timestamp attribute, as defined in <a href="#section-6.3.5">Section 6.3.5</a>.






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   The following attributes are required if a TSP is not providing a
   time-mark of the ES:

      - signature-time-stamp attribute, as defined in <a href="#section-6.1.1">Section 6.1.1</a>.

   If attributes certificates are used, then the following attributes
   may be present:

      - attribute-certificate-references attribute, defined in <a href="#section-6.2.3">Section</a>
        <a href="#section-6.2.3">6.2.3</a>;

      - attribute-revocation-references attribute, as defined in <a href="#section-6.2.4">Section</a>
        <a href="#section-6.2.4">6.2.4</a>.

   Other unsigned attributes may be present, but are not required.

+------------------------ CAdES-X-Type 1 ----------------------------+
|+---------------------------------- CAdES-C ------+                 |
||                                    +----------+ | +-------------+ |
||+--- CAdES-BES or CAdES-EPES ------+|Timestamp | | |             | |
|||                                  ||over      | | |             | |
|||+---------++----------++---------+||digital   | | |             | |
||||Signer's ||  Signed  || Digital |||signature | | | Timestamp   | |
||||Document ||Attributes||signature|||          | | |    over     | |
||||         ||          ||         |||Optional  | | |   CAdES-C   | |
|||+---------++----------++---------+||when      | | |             | |
||+----------------------------------+|timemarked| | |             | |
||                                    +----------+ | |             | |
||                                    +-----------+| +-------------+ |
||                                    |Complete   ||                 |
||                                    |certificate||                 |
||                                    |   and     ||                 |
||                                    |revocation ||                 |
||                                    |references ||                 |
||                                    +-----------+|                 |
|+-------------------------------------------------+                 |
|                                                                    |
+--------------------------------------------------------------------+

               Figure B.2: Illustration of CAdES-X Type 1











<span class="grey">Pinkas, et al.               Informational                     [Page 89]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-90" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


<span class="h4"><a class="selflink" id="appendix-B.1.3" href="#appendix-B.1.3">B.1.3</a>.  CAdES-X Type 2</span>

   An electronic signature with the additional validation data forming
   the eXtended Validation Data - Type 2 X is illustrated in Figure B.3
   and comprises the following:

      - CAdES-BES or CAdES-EPES, as defined in Sections <a href="#section-4.2">4.2</a>, <a href="#section-5.7">5.7</a>, or
        5.8;

      - complete-certificate-references attribute, as defined in <a href="#section-6.2.1">Section</a>
        <a href="#section-6.2.1">6.2.1</a>;

      - complete-revocation-references attribute, as defined in <a href="#section-6.2.2">Section</a>
        <a href="#section-6.2.2">6.2.2</a>;

      - time-stamped-certs-crls-references attribute, as defined in
        <a href="#section-6.3.6">Section 6.3.6</a>.

   The following attributes are required if a TSP is not providing a
   time-mark of the ES:

      - signature-time-stamp attribute, as defined in <a href="#section-6.1.1">Section 6.1.1</a>.

   If attributes certificates are used, then the following attributes
   may be present:

      - attribute-certificate-references attribute, defined in <a href="#section-6.2.3">Section</a>
        <a href="#section-6.2.3">6.2.3</a>;

      - attribute-revocation-references attribute, as defined in <a href="#section-6.2.4">Section</a>
        <a href="#section-6.2.4">6.2.4</a>.

   Other unsigned attributes may be present, but are not required.


















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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-91" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


+----------------------- CAdES-X-Type 2 -----------------------------+
|+-------------------------------------- CAdES-C --+                 |
||                                    +----------+ |                 |
||+-- CAdES-BES or CAdES-EPES -------+|Timestamp | |                 |
|||                                  ||over      | |                 |
|||+---------++----------++---------+||digital   | | +-------------+ |
||||         ||          ||         |||Signature | | | Timestamp   | |
||||Signer's ||  Signed  || Digital |||          | | | only over   | |
||||Document ||Attributes||signature|||Optional  | | | Complete    | |
||||         ||          ||         |||when      | | | certificate | |
|||+---------++----------++---------+||Timemarked| | |    and      | |
||+----------------------------------++----------+ | | revocation  | |
||                                    +-----------+| | references  | |
||                                    |Complete   || +-------------+ |
||                                    |certificate||                 |
||                                    |and        ||                 |
||                                    |revocation ||                 |
||                                    |references ||                 |
||                                    +-----------+|                 |
|+-------------------------------------------------+                 |
|                                                                    |
+--------------------------------------------------------------------+

               Figure B.3: Illustration of CAdES-X Type 2

<span class="h4"><a class="selflink" id="appendix-B.1.4" href="#appendix-B.1.4">B.1.4</a>.  CAdES-X Long Type 1 and CAdES-X Long Type 2</span>

   An electronic signature with the additional validation data forming
   the CAdES-X Long Type 1 and CAdES-X Long Type 2 is illustrated in
   Figure B.4 and comprises the following:

      - CAdES-BES or CAdES-EPES, as defined in Sections <a href="#section-4.3">4.3</a>, <a href="#section-5.7">5.7</a>, or
        5.8;

      - complete-certificate-references attribute, as defined in <a href="#section-6.2.1">Section</a>
        <a href="#section-6.2.1">6.2.1</a>;

      - complete-revocation-references attribute, as defined in <a href="#section-6.2.2">Section</a>
        <a href="#section-6.2.2">6.2.2</a>;

   The following attributes are required if a TSP is not providing a
   time-mark of the ES:

      - signature-time-stamp attribute, as defined in <a href="#section-6.1.1">Section 6.1.1</a>.







<span class="grey">Pinkas, et al.               Informational                     [Page 91]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-92" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


   The following attributes are required if the full certificate values
   and revocation values are not already included in the CAdES-BES or
   CAdES-EPES:

      - certificate-values attribute, as defined in <a href="#section-6.3.3">Section 6.3.3</a>;

      - revocation-values attribute, as defined in <a href="#section-6.3.4">Section 6.3.4</a>.

   If attributes certificates are used, then the following attributes
   may be present:

      - attribute-certificate-references attribute, defined in <a href="#section-6.2.3">Section</a>
        <a href="#section-6.2.3">6.2.3</a>;

      - attribute-revocation-references attribute, as defined in <a href="#section-6.2.4">Section</a>
        <a href="#section-6.2.4">6.2.4</a>.

   Plus one of the following attributes is required:

      - CAdES-C-Timestamp attribute, as defined in <a href="#section-6.3.5">Section 6.3.5</a>;

      - time-stamped-certs-crls-references attribute, as defined in
        <a href="#section-6.3.6">Section 6.3.6</a>.

   Other unsigned attributes may be present, but are not required.


























<span class="grey">Pinkas, et al.               Informational                     [Page 92]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-93" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


   +---------------------- CAdES-X-Type 1 or 2 ------------------------+
   |                                                   +--------------+|
   |+-------------------------------------- CAdES-C --+|+------------+||
   ||                                    +----------+ ||| Timestamp  |||
   ||+-- CAdES-BES or CAdES-EPES -------+|Timestamp | |||    over    |||
   |||                                  ||over      | |||  CAdES-C   |||
   |||+---------++----------++---------+||digital   | | +------------+ |
   ||||         ||          ||         |||signature | ||      or      ||
   ||||Signer's ||  Signed  || Digital |||          | ||+------------+||
   ||||Document ||Attributes||Signature|||Optional  | ||| Timestamp  |||
   ||||         ||          ||         |||when      | ||| only over  |||
   |||+---------++----------++---------+||timemarked| ||| complete   |||
   ||+----------------------------------++----------+ ||| certificate|||
   ||                                                 |||    and     |||
   ||                                    +-----------+||| revocation |||
   ||                                    |Complete   |||| references |||
   ||                                    |certificate|||+------------+||
   ||                                    |and        ||+--------------+|
   ||                                    |revocation || +------------+ |
   ||                                    |references || |Complete    | |
   ||                                    +-----------+| |certificate | |
   |+-------------------------------------------------+ |   and      | |
   |                                                    |revocation  | |
   |                                                    |  values    | |
   |                                                    +------------+ |
   +-------------------------------------------------------------------+

             Figure B.4: Illustration of CAdES-X Long Type 1
                         and CAdES-X Long Type 2

<span class="h3"><a class="selflink" id="appendix-B.2" href="#appendix-B.2">B.2</a>.  Time-Stamp Extensions</span>

   Each instance of the time-stamp attribute may include, as unsigned
   attributes in the signedData of the time-stamp, the following
   attributes related to the TSU:

      - complete-certificate-references attribute of the TSU, as defined
        in <a href="#section-6.2.1">Section 6.2.1</a>;

      - complete-revocation-references attribute of the TSU, as defined
        in <a href="#section-6.2.2">Section 6.2.2</a>;

      - certificate-values attribute of the TSU, as defined in <a href="#section-6.3.3">Section</a>
        <a href="#section-6.3.3">6.3.3</a>;

      - revocation-values attribute of the TSU, as defined in <a href="#section-6.3.4">Section</a>
        <a href="#section-6.3.4">6.3.4</a>.




<span class="grey">Pinkas, et al.               Informational                     [Page 93]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-94" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


   Other unsigned attributes may be present, but are not required.

<span class="h3"><a class="selflink" id="appendix-B.3" href="#appendix-B.3">B.3</a>.  Archive Validation Data (CAdES-A)</span>

   Before the algorithms, keys, and other cryptographic data used at the
   time the CAdES-C was built become weak and the cryptographic
   functions become vulnerable, or the certificates supporting previous
   time-stamps expire, the signed data, the CAdES-C, and any additional
   information (i.e., any CAdES-X) should be time-stamped.  If possible,
   this should use stronger algorithms (or longer key lengths) than in
   the original time-stamp.  This additional data and time-stamp is
   called Archive validation data required for the ES Archive format
   (CAdES-A).  The Time-stamping process may be repeated every time the
   protection used to time-stamp a previous CAdES-A becomes weak.  A
   CAdES-A may thus bear multiple embedded time-stamps.

   An example of an electronic signature (ES), with the additional
   validation data for the CAdES-C and CAdES-X forming the CAdES-A is
   illustrated in Figure B.5.
































<span class="grey">Pinkas, et al.               Informational                     [Page 94]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-95" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


+--------------------------- CAdES-A---------------------------------+
|+----------------------------------------------------+              |
||                                    +--------------+| +----------+ |
||+--------------------- CAdES-C ----+|+------------+|| |          | |
|||                     +----------+ ||| Timestamp  ||| |          | |
|||+-- CAdES-BES ------+|Timestamp | |||   over     ||| |          | |
||||   or CAdES-EPES   ||over      | |||  CAdES-C   ||| |  Archive | |
||||                   ||digital   | ||+------------+|| |          | |
||||                   ||signature | ||     or       || |Timestamp | |
||||                   ||          | ||+------------+|| |          | |
||||                   ||optional  | ||| Timestamp  ||| |          | |
||||                   ||when      | ||| only over  ||| |          | |
||||                   ||timemarked| ||| complete   ||| |          | |
|||+-------------------++----------+ ||| certificate||| +----------+ |
|||                                  |||    and     |||              |
|||                   +-------------+||| revocation |||              |
|||                   | Complete    |||| references |||              |
|||                   | certificate |||+------------+||              |
|||                   | and         ||+--------------+|              |
|||                   | revocation  || +------------+ |              |
|||                   | references  || |Complete    | |              |
|||                   +-------------+| |certificate | |              |
||+----------------------------------+ |   and      | |              |
||                                     |revocation  | |              |
||                                     |  values    | |              |
||                                     +------------+ |              |
|+----------------------------------------------------+              |
+--------------------------------------------------------------------+

                    Figure B.5: Illustration of CAdES-A

   The CAdES-A comprises the following elements:

      - the CAdES-BES or CAdES-EPES, including their signed and unsigned
        attributes;

      - complete-certificate-references attribute, as defined in <a href="#section-6.2.1">Section</a>
        <a href="#section-6.2.1">6.2.1</a>;

      - complete-revocation-references attribute, as defined in <a href="#section-6.2.2">Section</a>
        <a href="#section-6.2.2">6.2.2</a>.

   The following attributes are required if a TSP is not providing a
   time-mark of the ES:

      - signature-time-stamp attribute, as defined in <a href="#section-6.1.1">Section 6.1.1</a>.





<span class="grey">Pinkas, et al.               Informational                     [Page 95]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-96" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


   If attributes certificates are used, then the following attributes
   may be present:

      - attribute-certificate-references attribute, defined in <a href="#section-6.2.3">Section</a>
        <a href="#section-6.2.3">6.2.3</a>;

      - attribute-revocation-references attribute, as defined in <a href="#section-6.2.4">Section</a>
        <a href="#section-6.2.4">6.2.4</a>.

   The following attributes are required if the full certificate values
   and revocation values are not already included in the CAdES-BES or
   CAdES-EPES:

      - certificate-values attribute, as defined in <a href="#section-6.3.3">Section 6.3.3</a>;

      - revocation-values attribute, as defined in <a href="#section-6.3.4">Section 6.3.4</a>.

   At least one of the following two attributes is required:

      - CAdES-C-Timestamp attribute, as defined in <a href="#section-6.3.5">Section 6.3.5</a>;

      - time-stamped-certs-crls-references attribute, as defined in
        <a href="#section-6.3.6">Section 6.3.6</a>.

   The following attribute is required:

      - archive-time-stamp attributes, defined in <a href="#section-6.4.1">Section 6.4.1</a>.

   Several instances of the archive-time-stamp attribute may occur with
   an electronic signature, both over time and from different TSUs.  The
   time-stamp should be created using stronger algorithms (or longer key
   lengths) than in the original electronic signatures or time-stamps.

   Other unsigned attributes of the ES may be present, but are not
   required.

   The archive-time-stamp will itself contain the certificate and
   revocation information required to validate the archive-time-stamp;
   this may include the following unsigned attributes:

      - complete-certificate-references attribute of the TSU, as defined
        in <a href="#section-6.2.1">Section 6.2.1</a>;

      - complete-revocation-references attribute of the TSU, as defined
        in <a href="#section-6.2.2">Section 6.2.2</a>;

      - certificate-values attribute of the TSU, as defined in <a href="#section-6.3.3">Section</a>
        <a href="#section-6.3.3">6.3.3</a>;



<span class="grey">Pinkas, et al.               Informational                     [Page 96]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-97" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


      - revocation-values attribute of the TSU, as defined in <a href="#section-6.3.4">Section</a>
        <a href="#section-6.3.4">6.3.4</a>.

   Other unsigned attributes may be present, but are not required.

<span class="h3"><a class="selflink" id="appendix-B.4" href="#appendix-B.4">B.4</a>.  Example Validation Sequence</span>

   As described earlier, the signer or initial verifier may collect all
   the additional data that forms the electronic signature.  Figure B.6
   and the subsequent description describe how the validation process
   may build up a complete electronic signature over time.

+------------------------------------------ CAdES-C -------------+
|+------------------------------- CAdES-T ------+                |
||+-------------- CAdES ------------+           |                |
|||+--------------------++---------+|+---------+|  +-----------+ |
|||| ________           ||         |||Timestamp||  |Complete   | |
|||||Sign.Pol|          ||Digital  |||over     ||  |certificate| |
|||||  Id.   | Signed   ||signature|||digital  ||  |   and     | |
||||| option.|attributes||         |||signature||  |revocation | |
|||||________|          |+---------+|+---------+|  |references | |
|||+--------------------+           |    ^      |  +-----------+ |
||+---------------------------------+    |      |        ^       |
||                     1 |              /       |        |       |
|+---------------------- | ------------/--------+        |       |
+----------------------- | ---------- / --------------- / -------+
                         |           /2    ----3--------
      +----------+       |          /     /
      |          |       v         /     |
      | Signer's |      +---------------------+     +-------------+
      | document |-----&gt;| Validation Process  |----&gt;|- Valid      |
      |          |      +---------------------+ 4   |- Invalid    |
      +----------+           |  ^       |  ^        |- Validation |
                             v  |       v  |        |  Incomplete |
                         +---------+ +--------+     +-------------+
                         |Signature| |Trusted |
                         | Policy  | |Service |
                         | Issuer  | |Provider|
                         +---------+ +--------+

       Figure B.6: Illustration of a CAdES validation sequence

   Soon after receiving the electronic signature (CAdES) from the signer
   (1), the digital signature value may be checked; the validation
   process shall at least add a time-stamp (2), unless the signer has
   provided one which is trusted by the verifier.  The validation
   process may also validate the electronic signature using additional
   data (e.g., certificates, CRL, etc.) provided by Trusted Service



<span class="grey">Pinkas, et al.               Informational                     [Page 97]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-98" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


   Providers.  When applicable, the validation process will also need to
   conform to the requirements specified in a signature policy.  If the
   validation process is validation incomplete, then the output from
   this stage is the CAdES-T.

   To ascertain the validity status as Valid or Invalid and communicate
   that to the user (4), all the additional data required to validate
   the CAdES-C must be available (e.g., the complete certificate and
   revocation information).

   Once the data needed to complete validation data references (CAdES-C)
   is available, then the validation process should:

      - obtain all the necessary additional certificates and revocation
        status information;

      - complete all the validation checks on the ES using the complete
        certificate and revocation information (if a time-stamp is not
        already present, this may be added at the same stage, combining
        the CAdES-T and CAdES-C processes);

      - record the complete certificate and revocation references (3);

      - indicate the validity status to the user (4).

   At the same time as the validation process creates the CAdES-C, the
   validation process may provide and/or record the values of
   certificates and revocation status information used in CAdES-C (5).
   The end result is called CAdES-X Long.

   This is illustrated in Figure B.7.




















<span class="grey">Pinkas, et al.               Informational                     [Page 98]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-99" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


+----------------------------------------------------- CAdES-X Long -+
|+------------------------------- CAdES-C -------------+             |
||+-------------- CAdES ------------+                  |             |
|||+--------------------++---------+|+---------+       |+-----------+|
|||| ________           ||         |||Timestamp|       ||Complete   ||
|||||Sign.Pol|          ||Digital  |||over     |       ||certificate||
|||||  Id.   | Signed   ||signature|||digital  |       ||   and     ||
||||| option.|attributes||         |||signature|       ||revocation ||
|||||________|          ||         ||+---------+       ||  values   ||
|||+--------------------++---------+|  ^  +-----------+|+-----------+|
||+---------------------------------+  |  |Complete   ||      ^      |
||                         |           |  |certificate||      |      |
||                         |         2 |  |   and     ||      |      |
||                         |           |  |revocation ||      |      |
||                         |           |  |references ||      |      |
||                       1 |          /   +-----------+|      |      |
|+------------------------ | ------- / --------- ^-----+     /       |
+------------------------- | ------ / ---------- |--------- / -------+
                           |       /      ----- /  ------- /
      +----------+         |      /      /  3     /   5
      |          |         v     |      |        |
      | Signer's |      +--------------------+      +-----------+
      | document |-----&gt;| Validation Process |-----&gt;| - Valid   |
      |          |      +--------------------+  4   | - Invalid |
      +----------+          |  ^       |  ^         +-----------+
                            v  |       v  |
                        +---------+ +--------+
                        |Signature| |Trusted |
                        | Policy  | |Service |
                        | Issuer  | |Provider|
                        +---------+ +--------+

          Figure B.7: Illustration of a CAdES validation sequence
                      with CAdES-X Long

   When the validation process creates the CAdES-C, it may also create
   extended forms of validation data.

   A first alternative is to time-stamp all data forming the CAdES-X
   Type 1.

   This is illustrated in Figure B.8.









<span class="grey">Pinkas, et al.               Informational                     [Page 99]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-100" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


+------------------------------------------------ CAdES-X Type 1 -----+
|+------------------------------- CAdES-C ------------------+         |
||+-------------- CAdES ------------+                       |         |
|||+--------------------++---------+|+---------++----------+|+-------+|
|||| ________           ||         |||Timestamp|| Complete |||       ||
|||||Sign.Pol|          ||Digital  |||over     ||  cert.   |||Time-  ||
|||||  Id.   | Signed   ||signature|||digital  ||   and    |||stamp  ||
||||| option.|attributes||         |||signature||  revoc.  ||| over  ||
|||||________|          |+---------+|+---------+|references|||CAdES-C||
|||+--------------------+           |    ^      |          |||       ||
||+---------------------------------+    |      +----------+|+-------+|
||                         |             |            ^     |    ^    |
||                       1 |            /             |     |    |    |
|+------------------------ | --------- / ----------- / -----+    |    |
+------------------------- | -------- / ----------- / --------- / ----+
                           |       2 /     ---3----            /
      +----------+         |        /    /   -----------5------
      |          |         v       |    |  /
      | Signer's |      +--------------------+       +-----------+
      | document |-----&gt;| Validation Process |-----&gt; | - Valid   |
      |          |      +--------------------+  4    | - Invalid |
      +----------+          |  ^       |  ^          +-----------+
                            v  |       v  |
                        +---------+ +--------+
                        |Signature| |Trusted |
                        | Policy  | |Service |
                        | Issuer  | |Provider|
                        +---------+ +--------+

    Figure B.8: Illustration of CAdES with eXtended validation data
                CAdES-X Type 1

   Another alternative is to time-stamp the certificate and revocation
   information references used to validate the electronic signature (but
   not the signature) (6).  The end result is called CAdES-X Type 2.

   This is illustrated in Figure B.9.














<span class="grey">Pinkas, et al.               Informational                    [Page 100]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-101" ></span>
<span class="grey"><a href="./rfc5126">RFC 5126</a>           CMS Advanced Electronic Signatures      February 2008</span>


+-------------------------------------------- CAdES-X Type 2 --------+
|+------------------------------- CAdES-C -------------+             |
||+-------------- CAdES ------------+                  |             |
|||+--------------------++---------+|+---------+       |+-----------+|
|||| ________           ||         |||Timestamp|       ||Timestamp  ||
|||||Sign.Pol|          ||         |||over     |       ||   over    ||
|||||  Id.   | Signed   ||Digital  |||digital  |       ||complete   ||
||||| option.|attributes||signature|||signature|       ||certificate||
|||||________|          ||         |||         |       ||           ||
|||+--------------------++---------+|+---------+       ||   and     ||
||+---------------------------------+  ^  +-----------+||revocation ||
||                         |           |  |Complete   |||references ||
||                         |           |  |certificate||+-----------+|
||                         |           |  |   and     ||     ^       |
||                       1 |         2 |  |revocation ||     |       |
||                         |           |  |references ||     |       |
||                         |           |  +-----------+|     |       |
|+------------------------ | --------- | --- ^ --------+     |       |
|                          |           |   3 |              /        |
|                          |           |    /    ----------          |
|                          |          /    /    /   6                |
|                          |         /    /    /                     |
|                          |        /    /    /                      |
+------------------------- | ----- | -- | -- / ----------------------+
                           |       |    |   |
                           v       |    |   |
                        +--------------------+      +-----------+
                        | Validation Process |-----&gt;| - Valid   |
                        +--------------------+  4   | - Invalid |
                            |  ^       |  ^         +-----------+
                            v  |       v  |
                        +---------+ +--------+
                        |Signature| |Trusted |
                        | Policy  | |Service |
                        | Issuer  | |Provider|
                        +---------+ +--------+

   Figure B.9: Illustration of CAdES with eXtended validation data
               CAdES-X Type 2

   Before the algorithms used in any of the electronic signatures become
   or are likely to be compromised or rendered vulnerable in the future,
   it may be necessary to time-stamp the entire electronic signature,
   including all the values of the validation and user data as an ES
   with Archive validation data (CAdES-A) (7).

   A CAdES-A is illustrated in Figure B.10.




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+----------------------------- CAdES-A ---------------------------+
|                                                                 |
|  +-- CAdES-X Long Type 1 or 2  ----------+                      |
|  |                                       |   +------------+     |
|  |                                       |   |            |     |
|  |                                       |   |  Archive   |     |
|  |                                       |   | Time-stamp |     |
|  |                                       |   |            |     |
|  |                                       |   +------------+     |
|  +---------------------------------------+         ^            |
|  +----------+          ^   ^   ^   ^               |            |
|  |          |          |   |   |   |              /             |
|  | Signers' |          |   |   |   |             /              |
|  | Document |\         |   |   |   |            /               |
|  |          | \ 1    2 | 3 | 5 | 6 |         7 /                |
|  +----------+  \       |   |   |   |          /                 |
|                 \      |   |   |   |         /                  |
+----------------- \ --- | - | - | - | ------ / ------------------+
                    \    |   |   |   |       |
                     |   |   |   |   |       |
                     |   |   |   |   |       |
                     v   v   |   |   |       |
                 +-----------------------------+      +-----------+
                 |      Validation Process     |-----&gt;| - Valid   |
                 +-----------------------------+  4   | - Invalid |
                     |  ^       |  ^                  +-----------+
                     v  |       v  |
                 +---------+ +--------+
                 |Signature| |Trusted |
                 | Policy  | |Service |
                 | Issuer  | |Provider|
                 +---------+ +--------+

                 Figure B.10: Illustration of CAdES-A

<span class="h3"><a class="selflink" id="appendix-B.5" href="#appendix-B.5">B.5</a>.  Additional Optional Features</span>

   The present document also defines additional optional features to:

      - indicate a commitment type being made by the signer;

      - indicate the claimed time when the signature was done;

      - indicate the claimed location of the signer;

      - indicate the claimed or certified role under which a signature
        was created;




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      - support counter signatures;

      - support multiple signatures.

Annex C (Informative): General Description

   This annex explains some of the concepts and provides the rationale
   for normative parts of the present document.

   The specification below includes a description of why and when each
   component of an electronic signature is useful, with a brief
   description of the vulnerabilities and threats and the manner by
   which they are countered.

<span class="h3"><a class="selflink" id="appendix-C.1" href="#appendix-C.1">C.1</a>.  The Signature Policy</span>

   The signature policy is a set of rules for the creation and
   validation of an electronic signature, under which the signature can
   be determined to be valid.  A given legal/contractual context may
   recognize a particular signature policy as meeting its requirements.
   A signature policy may be issued, for example, by a party relying on
   the electronic signatures and selected by the signer for use with
   that relying party.  Alternatively, a signature policy may be
   established through an electronic trading association for use amongst
   its members.  Both the signer and verifier use the same signature
   policy.

   The signature policy may be explicitly identified or may be implied
   by the semantics of the data being signed and other external data,
   like a contract being referenced, which itself refers to a signature
   policy.  An explicit signature policy has a globally unique
   reference, which is bound to an electronic signature by the signer as
   part of the signature calculation.

   The signature policy needs to be available in human readable form so
   that it can be assessed to meet the requirements of the legal and
   contractual context in which it is being applied.  To facilitate the
   automatic processing of an electronic signature, the parts of the
   signature policy, which specify the electronic rules for the creation
   and validation of the electronic signature, also need to be
   comprehensively defined and in a computer-processable form.

   The signature policy thus includes the following:

      - rules that apply to technical validation of a particular
        signature;





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      - rules that may be implied through adoption of Certificate
        Policies that apply to the electronic signature (e.g., rules for
        ensuring the secrecy of the private signing key);

      - rules that relate to the environment used by the signer, e.g.,
        the use of an agreed CAD (Card Accepting Device) used in
        conjunction with a smart card.

   For example, the major rules required for technical validation can
   include:

      - recognized root keys or "top-level certification authorities";

      - acceptable certificate policies (if any);

      - necessary certificate extensions and values (if any);

      - the need for the revocation status for each component of the
        certification tree;

      - acceptable TSAs (if time-stamp tokens are being used);

      - acceptable organizations for keeping the audit trails with
        time-marks (if time-marking is being used);

      - acceptable AAs (if any are being used),and;

      - rules defining the components of the electronic signature that
        shall be provided by the signer with data required by the
        verifier when required to provide long-term proof.

<span class="h3"><a class="selflink" id="appendix-C.2" href="#appendix-C.2">C.2</a>.  Signed Information</span>

   The information being signed may be defined as a MIME-encapsulated
   message that can be used to signal the format of the content in order
   to select the right display or application.  It can be composed of
   formatted data, free text, or fields from an electronic form
   (e-form).  For example, the Adobe(tm) format "pdf" or the eXtensible
   Mark up Language (XML) may be used.  Annex D defines how the content
   may be structured to indicate the type of signed data using MIME.

<span class="h3"><a class="selflink" id="appendix-C.3" href="#appendix-C.3">C.3</a>.  Components of an Electronic Signature</span>

<span class="h4"><a class="selflink" id="appendix-C.3.1" href="#appendix-C.3.1">C.3.1</a>.  Reference to the Signature Policy</span>

   When two independent parties want to evaluate an electronic
   signature, it is fundamental that they get the same result.  This
   requirement can be met using comprehensive signature policies that



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   ensure consistency of signature validation.  Signature policies can
   be identified implicitly by the data being signed, or they can be
   explicitly identified using the CAdES-EPES form of electronic
   signature; the CAdES-EPES mandates a consistent signature policy must
   be used by both the signer and verifier.

   By signing over the Signature Policy Identifier in the CAdES-EPES,
   the signer explicitly indicates that he or she has applied the
   signature policy in creating the signature.

   In order to unambiguously identify the details of an explicit
   signature policy that is to be used to verify a CAdES-EPES, the
   signature, an identifier, and hash of the "Signature policy" shall be
   part of the signed data.  Additional information about the explicit
   policy (e.g., web reference to the document) may be carried as
   "qualifiers" to the Signature Policy Identifier.

   In order to unambiguously identify the authority responsible for
   defining an explicit signature policy, the "Signature policy" can be
   signed.

<span class="h4"><a class="selflink" id="appendix-C.3.2" href="#appendix-C.3.2">C.3.2</a>.  Commitment Type Indication</span>

   The commitment type can be indicated in the electronic signature
   either:

      - explicitly using a "commitment type indication" in the
        electronic signature;

      - implicitly or explicitly from the semantics of the signed data.

   If the indicated commitment type is explicit using a "commitment type
   indication" in the electronic signature, acceptance of a verified
   signature implies acceptance of the semantics of that commitment
   type.  The semantics of explicit commitment type indications may be
   subject to signer and verifier agreement, specified as part of the
   signature policy or registered for generic use across multiple
   policies.

   If a CAdES-EPES electronic signature format is used and the
   electronic signature includes a commitment type indication other than
   one of those recognized under the signature policy, the signature
   shall be treated as invalid.

   How commitment is indicated using the semantics of the data being
   signed is outside the scope of the present document.





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      NOTE: Examples of commitment indicated through the semantics of
      the data being signed are:

      - an explicit commitment made by the signer indicated by the type
        of data being signed over.  Thus, the data structure being
        signed can have an explicit commitment within the context of the
        application (e.g., EDIFACT purchase order);

      - an implicit commitment that is a commitment made by the signer
        because the data being signed over has specific semantics
        (meaning), which is only interpretable by humans, (i.e., free
        text).

<span class="h4"><a class="selflink" id="appendix-C.3.3" href="#appendix-C.3.3">C.3.3</a>.  Certificate Identifier from the Signer</span>

   In many real-life environments, users will be able to get from
   different CAs or even from the same CA, different certificates
   containing the same public key for different names.  The prime
   advantage is that a user can use the same private key for different
   purposes.  Multiple use of the private key is an advantage when a
   smart card is used to protect the private key, since the storage of a
   smart card is always limited.  When several CAs are involved, each
   different certificate may contain a different identity, e.g., as a
   citizen of a nation or as an employee from a company.  Thus, when a
   private key is used for various purposes, the certificate is needed
   to clarify the context in which the private key was used when
   generating the signature.  Where there is the possibility that
   multiple private keys are used, it is necessary for the signer to
   indicate to the verifier the precise certificate to be used.

   Many current schemes simply add the certificate after the signed data
   and thus are vulnerable to substitution attacks.  If the certificate
   from the signer was simply appended to the signature and thus not
   protected by the signature, anyone could substitute one certificate
   for another, and the message would appear to be signed by someone
   else.  In order to counter this kind of attack, the identifier of the
   signer has to be protected by the digital signature from the signer.

   In order to unambiguously identify the certificate to be used for the
   verification of the signature, an identifier of the certificate from
   the signer shall be part of the signed data.

<span class="h4"><a class="selflink" id="appendix-C.3.4" href="#appendix-C.3.4">C.3.4</a>.  Role Attributes</span>

   While the name of the signer is important, the position of the signer
   within a company or an organization is of paramount importance as
   well.  Some information (i.e., a contract) may only be valid if
   signed by a user in a particular role, e.g., a Sales Director.  In



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   many cases, who the sales Director really is, is not that important,
   but being sure that the signer is empowered by his company to be the
   Sales Director is fundamental.

   The present document defines two different ways for providing this
   feature:

      - by placing a claimed role name in the CMS signed attributes
        field;

      - by placing an attribute certificate containing a certified role
        name in the CMS signed attributes field.

      NOTE: Another possible approach would have been to use additional
      attributes containing the roles name(s) in the signer's identity
      certificate.  However, it was decided not to follow this approach
      as it significantly complicates the management of certificates.
      For example, by using separate certificates for the signer's
      identity and roles means new identity keys need not be issued if a
      user's role changes.

<span class="h5"><a class="selflink" id="appendix-C.3.4.1" href="#appendix-C.3.4.1">C.3.4.1</a>.  Claimed Role</span>

   The signer may be trusted to state his own role without any
   certificate to corroborate this claim; in which case, the claimed
   role can be added to the signature as a signed attribute.

<span class="h5"><a class="selflink" id="appendix-C.3.4.2" href="#appendix-C.3.4.2">C.3.4.2</a>.  Certified Role</span>

   Unlike public key certificates that bind an identifier to a public
   key, Attribute Certificates bind the identifier of a certificate to
   some attributes, like a role.  An Attribute Certificate is NOT issued
   by a CA but by an Attribute Authority (AA).  The Attribute Authority,
   in most cases, might be under the control of an organization or a
   company that is best placed to know which attributes are relevant for
   which individual.  The Attribute Authority may use or point to public
   key certificates issued by any CA, provided that the appropriate
   trust may be placed in that CA.  Attribute Certificates may have
   various periods of validity.  That period may be quite short, e.g.,
   one day.  While this requires that a new Attribute Certificate be
   obtained every day, valid for that day, this can be advantageous
   since revocation of such certificates may not be needed.  When
   signing, the signer will have to specify which Attribute Certificate
   it selects.  In order to do so, the Attribute Certificate will have
   to be included in the signed data in order to be protected by the
   digital signature from the signer.





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   In order to unambiguously identify the attribute certificate(s) to be
   used for the verification of the signature, an identifier of the
   attribute certificate(s) from the signer shall be part of the signed
   data.

<span class="h4"><a class="selflink" id="appendix-C.3.5" href="#appendix-C.3.5">C.3.5</a>.  Signer Location</span>

   In some transactions, the purported location of the signer at the
   time he or she applies his signature may need to be indicated.  For
   this reason, an optional location indicator shall be able to be
   included.

   In order to provide indication of the location of the signer at the
   time he or she applied his signature, a location attribute may be
   included in the signature.

<span class="h4"><a class="selflink" id="appendix-C.3.6" href="#appendix-C.3.6">C.3.6</a>.  Signing Time</span>

   The present document provides the capability to include a claimed
   signing time as an attribute of an electronic signature.

   Using this attribute, a signer may sign over a time that is the
   claimed signing time.  When an ES with Time is created (CAdES-T),
   then either a trusted time-stamp is obtained and added to the ES or a
   trusted time-mark exists in an audit trail.  When a verifier accepts
   a signature, the two times shall be within acceptable limits.

   A further optional attribute is defined in the present document to
   time-stamp the content and to provide proof of the existence of the
   content, at the time indicated by the time-stamp token.

   Using this optional attribute, a trusted secure time may be obtained
   before the document is signed and included under the digital
   signature.  This solution requires an online connection to a trusted
   time-stamping service before generating the signature and may not
   represent the precise signing time, since it can be obtained in
   advance.  However, this optional attribute may be used by the signer
   to prove that the signed object existed before the date included in
   the time-stamp (see <a href="#section-5.11.4">Section 5.11.4</a>).

<span class="h4"><a class="selflink" id="appendix-C.3.7" href="#appendix-C.3.7">C.3.7</a>.  Content Format</span>

   When presenting signed data to a human user, it may be important that
   there is no ambiguity as to the presentation of the signed
   information to the relying party.  In order for the appropriate
   representation (text, sound, or video) to be selected by the relying
   party when data (as opposed to data that has been further signed or
   encrypted) is encapsulated in the SignedData (indicated by the



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   eContentType within EncapsulatedContentInfo being set to id-data),
   further typing information should be used to identify the type of
   document being signed.  This is generally achieved using the MIME
   content typing and encoding mechanism defined in <a href="./rfc2045">RFC 2045</a> [<a href="#ref-6" title="&quot;Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies&quot;">6</a>]).
   Further information on the use of MIME is given in Annex F.

<span class="h4"><a class="selflink" id="appendix-C.3.8" href="#appendix-C.3.8">C.3.8</a>.  content-hints</span>

   The contents-hints attribute provides information on the innermost
   signed content of a multi-layer message where one content is
   encapsulated in another.  This may be useful if the signed data is
   itself encrypted.

<span class="h4"><a class="selflink" id="appendix-C.3.9" href="#appendix-C.3.9">C.3.9</a>.  Content Cross-Referencing</span>

   When presenting a signed data is in relation to another signed data,
   it may be important to identify the signed data to which it relates.
   The content-reference and content-identifier attributes, as defined
   in ESS (<a href="./rfc2634">RFC 2634</a> [<a href="#ref-5" title="&quot;Enhanced Security Services for S/MIME&quot;">5</a>]), provide the ability to link a request and
   reply messages in an exchange between two parties.

<span class="h3"><a class="selflink" id="appendix-C.4" href="#appendix-C.4">C.4</a>.  Components of Validation Data</span>

<span class="h4"><a class="selflink" id="appendix-C.4.1" href="#appendix-C.4.1">C.4.1</a>.  Revocation Status Information</span>

   A verifier will have to ascertain that the certificate of the signer
   was valid at the time of the signature.  This can be done by either:

      - using Certificate Revocation Lists (CRLs);

      - using responses from an online certificate status server (for
        example, obtained through the OCSP protocol).

      NOTE 1: The time of the signature may not be known, so
      time-stamping or time-marking may be used to provide the time
      indication of when it was known that the signature existed.

      NOTE 2: When validating an electronic signature and checking
      revocation status information, if a "grace period" is required, it
      needs to be suitably long enough to allow the involved authority
      to process a "last-minute" revocation request and for the request
      to propagate through the revocation system.  This grace period is
      to be added to the time included with the time-stamp token or the
      time-mark, and thus the revocation status information should be
      captured after the end of the grace period.






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<span class="h5"><a class="selflink" id="appendix-C.4.1.1" href="#appendix-C.4.1.1">C.4.1.1</a>.  CRL Information</span>

   When using CRLs to get revocation information, a verifier will have
   to make sure that he or she gets, at the time of the first
   verification, the appropriate certificate revocation information from
   the signer's CA.  This should be done as soon as possible to minimize
   the time delay between the generation and verification of the
   signature.  However, a "grace period" is required to allow CAs time
   to process revocation requests.

   For example, a revocation request may arrive at a CA just before
   issuing the next CRL, and there may not enough time to include the
   revised revocation status information.  This involves checking that
   the signer certificate serial number is not included in the CRL.
   Either the signer, the initial verifier, or a subsequent verifier may
   obtain this CRL.  If obtained by the signer, then it shall be
   conveyed to the verifier.  It may be convenient to archive the CRL
   for ease of subsequent verification or arbitration.  Alternatively,
   provided the CRL is archived elsewhere, which is accessible for the
   purpose of arbitration, then the serial number of the CRL used may be
   archived together with the verified electronic signature as a CAdES-C
   form.

   Even if the certificate serial number appears in the CRL with the
   status "suspended" (i.e., on hold), the signature is not to be deemed
   as valid since a suspended certificate is not supposed to be used
   even by its rightful owner.

<span class="h5"><a class="selflink" id="appendix-C.4.1.2" href="#appendix-C.4.1.2">C.4.1.2</a>.  OCSP Information</span>

   When using OCSP to get revocation information, a verifier will have
   to make sure that he or she gets, at the time of the first
   verification, an OCSP response that contains the status "valid".
   This should be done as soon as possible after the generation of the
   signature, still providing a "grace period" suitable enough to allow
   the involved authority to process a "last-minute" revocation request.
   The signer, the verifier, or any other third party may fetch this
   OCSP response.  Since OCSP responses are transient and thus are not
   archived by any TSP, including CA, it is the responsibility of every
   verifier to make sure that it is stored in a safe place.  The
   simplest way is to store them associated with the electronic
   signature.  An alternative would be to store them so that they can
   then be easily retrieved and incorporate references to them in the
   electronic signature itself as a CAdES-C form.







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   In the same way as for the case of the CRL, it may happen that the
   certificate is declared as invalid but with the secondary status
   "suspended".  In such a case, the same comment as for the CRL
   applies.

<span class="h4"><a class="selflink" id="appendix-C.4.2" href="#appendix-C.4.2">C.4.2</a>.  Certification Path</span>

   A verifier may have to ascertain that the certification path was
   valid, at the time of the signature, up to a trust point, according
   to the:

      - naming constraints;
      - certificate policy constraints;
      - signature policy, when applicable.

   Since the time of the signature cannot be known with certainty, an
   upper limit of it should be used as indicated by either the
   time-stamp or time-mark.

   In this case, it will be necessary to capture all the certificates
   from the certification path, starting with those from the signer and
   ending up with those of the self-signed certificate from one trusted
   root; when applicable, this may be specified as part of the Signature
   Policy.  In addition, it will be necessary to capture the Certificate
   Authority Revocation Lists (CARLs) to prove that none of the CAs from
   the chain were revoked at the time of the signature.  Again, all this
   material may be incorporated in the electronic signature (ES X
   forms).  An alternative would be to store this information so that it
   can be easily retrieved and incorporate references to it in the
   electronic signature itself as a CAdES-C form.

<span class="h4"><a class="selflink" id="appendix-C.4.3" href="#appendix-C.4.3">C.4.3</a>.  Time-Stamping for Long Life of Signatures</span>

   An important property for long-standing signatures is that a
   signature, having been found once to be valid, shall continue to be
   so months or years later.

   A signer, verifier, or both may be required to provide, on request,
   proof that a digital signature was created or verified during the
   validity period of all the certificates that make up the certificate
   path.  In this case, the signer, verifier, or both will also be
   required to provide proof that the signer's certificate and all the
   CA certificates used to form a valid certification path were not
   revoked when the signature was created or verified.







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   It would be quite unacceptable to consider a signature as invalid
   even if the keys or certificates were later compromised.  Thus, there
   is a need to be able to demonstrate that the signature keys were
   valid at the time that the signature was created to provide long-term
   evidence of the validity of a signature.

   It could be the case that a certificate was valid at the time of the
   signature but revoked some time later.  In this event, evidence shall
   be provided that the document was signed before the signing key was
   revoked.  Time-stamping by a Time-Stamping Authority (TSA) can
   provide such evidence.  A time-stamp is obtained by sending the hash
   value of the given data to the TSA.  The returned "time-stamp" is a
   signed document that contains the hash value, the identity of the
   TSA, and the time of stamping.  This proves that the given data
   existed before the time of stamping.  Time-stamping a digital
   signature (by sending a hash of the signature to the TSA) before the
   revocation of the signer's private key provides evidence that the
   signature had been created before the certificate was revoked.

   If a recipient wants to hold a valid electronic signature, he will
   have to ensure that he has obtained a valid time-stamp for it before
   that key (and any key involved in the validation) is revoked.  The
   sooner the time-stamp is obtained after the signing time, the better.
   Any time-stamp or time-mark that is taken after the expiration date
   of any certificate in the certification path has no value in proving
   the validity of a signature.

   It is important to note that signatures may be generated "off-line"
   and time-stamped at a later time by anyone, for example, by the
   signer or any recipient interested in the value of the signature.
   The time-stamp can thus be provided by the signer, together with the
   signed document, or obtained by the recipient following receipt of
   the signed document.

   The time-stamp is NOT a component of the Basic Electronic Signature,
   but it is the essential component of the ES with Time.

   It is required, in the present document, that if a signer's digital
   signature value is to be time-stamped, the time-stamp token is issued
   by a trusted source, known as a Time-Stamping Authority.

   The present document requires that the signer's digital signature
   value be time-stamped by a trusted source before the electronic
   signature can become an ES with Complete validation data.  Acceptable
   TSAs may be specified in a Signature Validation Policy.

   This technique is referred to as CAdES-C in the present document.




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   Should both the signer and verifier be required to time-stamp the
   signature value to meet the requirements of the signature policy, the
   signature policy may specify a permitted time delay between the two
   time-stamps.

<span class="h4"><a class="selflink" id="appendix-C.4.4" href="#appendix-C.4.4">C.4.4</a>.  Time-Stamping for Long Life of Signature before CA Key</span>
        Compromises

   Time-stamped, extended electronic signatures are needed when there is
   a requirement to safeguard against the possibility of a CA key in the
   certificate chain ever being compromised.  A verifier may be required
   to provide, on request, proof that the certification path and the
   revocation information used at the time of the signature were valid,
   even in the case where one of the issuing keys or OCSP responder keys
   is later compromised.

   The present document defines two ways of using time-stamps to protect
   against this compromise:

      - time-stamp the ES with Complete validation data, when an OCSP
        response is used to get the status of the certificate from the
        signer (CAdES-X Type 1).  This format is suitable to be used
        with an OCSP response, and it offers the additional advantage of
        providing an integrity protection over the whole data;

      - time-stamp only the certification path and revocation
        information references when a CRL is used to get the status of
        the certificate from the signer (CAdES-X Type2).  This format is
        suitable to be used with CRLs, since the time-stamped
        information may be used for more than one signature (when
        signers have their certificates issued by the same CA and when
        signatures can be checked using the same CRLs).

      NOTE: The signer, verifier, or both may obtain the time-stamp.

<span class="h5"><a class="selflink" id="appendix-C.4.4.1" href="#appendix-C.4.4.1">C.4.4.1</a>.  Time-Stamping the ES with Complete Validation Data (CAdES-X</span>
          Type 1)

   When an OCSP response is used, it is necessary to time-stamp in
   particular that response in the case the key from the responder would
   be compromised.  Since the information contained in the OCSP response
   is user specific and time specific, an individual time-stamp is
   needed for every signature received.  Instead of placing the
   time-stamp only over the certification path references and revocation
   information references, which include the OCSP response, the
   time-stamp is placed on the CAdES-C.  Since the certification path
   and revocation information references are included in the ES with
   Complete validation data, they are also protected.  For the same



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   cryptographic price, this provides an integrity mechanism over the ES
   with Complete validation data.  Any modification can be immediately
   detected.  It should be noticed that other means of
   protecting/detecting the integrity of the ES with Complete validation
   data exist and could be used.  Although the technique requires a
   time-stamp for every signature, it is well suited for individual
   users wishing to have an integrity-protected copy of all the
   validated signatures they have received.

   By time-stamping the complete electronic signature, including the
   digital signature as well as the references to the certificates and
   revocation status information used to support validation of that
   signature, the time-stamp ensures that there is no ambiguity in the
   means of validating that signature.

   This technique is referred to as CAdES-X Type 1 in the present
   document.

      NOTE: Trust is achieved in the references by including a hash of
      the data being referenced.

   If it is desired for any reason to keep a copy of the additional data
   being referenced, the additional data may be attached to the
   electronic signature, in which case the electronic signature becomes
   a CAdES-X Long Type 1, as defined by the present document.

   A CAdES-X Long Type 1 is simply the concatenation of a CAdES-X Type
   1, with a copy of the additional data being referenced.

<span class="h5"><a class="selflink" id="appendix-C.4.4.2" href="#appendix-C.4.4.2">C.4.4.2</a>.  Time-Stamping Certificates and Revocation Information</span>
          References (CAdES-X Type 2)

   Time-stamping each ES with Complete validation data, as defined
   above, may not be efficient, particularly when the same set of CA
   certificates and CRL information is used to validate many signatures.

   Time-stamping CA certificates will stop any attacker from issuing
   bogus CA certificates that could be claimed to exist before the CA
   key was compromised.  Any bogus time-stamped CA certificates will
   show that the certificate was created after the legitimate CA key was
   compromised.  In the same way, time-stamping CA CRLs will stop any
   attacker from issuing bogus CA CRLs that could be claimed to exist
   before the CA key was compromised.

   Time-stamping of commonly used certificates and CRLs can be done
   centrally, e.g., inside a company or by a service provider.  This
   method reduces the amount of data the verifier has to time-stamp; for
   example, it could be reduced to just one time-stamp per day (i.e., in



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   the case where all the signers use the same CA, and the CRL applies
   for the whole day).  The information that needs to be time-stamped is
   not the actual certificates and CRLs, but the unambiguous references
   to those certificates and CRLs.

   This technique is referred to as CAdES-X Type 2 in the present
   document and requires the following:

      - all the CA certificates references and revocation information
        references (i.e., CRLs) used in validating the CAdES-C are
        covered by one or more time-stamps.

   Thus, a CAdES-C with a time-stamp signature value at time T1 can be
   proved valid if all the CA and CRL references are time-stamped at
   time T1+.

<span class="h4"><a class="selflink" id="appendix-C.4.5" href="#appendix-C.4.5">C.4.5</a>.  Time-Stamping for Archive of Signature</span>

   Advances in computing increase the probability of being able to break
   algorithms and compromise keys.  There is therefore a requirement to
   be able to protect electronic signatures against this possibility.

   Over a period of time, weaknesses may occur in the cryptographic
   algorithms used to create an electronic signature (e.g., due to the
   time available for cryptoanalysis, or improvements in
   cryptoanalytical techniques).  Before such weaknesses become likely,
   a verifier should take extra measures to maintain the validity of the
   electronic signature.  Several techniques could be used to achieve
   this goal, depending on the nature of the weakened cryptography.  In
   order to simplify matters, a single technique called Archive
   validation data, covering all the cases, is being used in the present
   document.

   Archive validation data consists of the validation data and the
   complete certificate and revocation data, time-stamped together with
   the electronic signature.  The Archive validation data is necessary
   if the hash function and the crypto algorithms that were used to
   create the signature are no longer secure.  Also, if it cannot be
   assumed that the hash function used by the Time-Stamping Authority is
   secure, then nested time-stamps of the Archived Electronic Signature
   are required.

   The potential for a Trusted Service Provider (TSP) key compromise
   should be significantly lower than user keys because TSP(s) are
   expected to use stronger cryptography and better key protection.  It
   can be expected that new algorithms (or old ones with greater key
   lengths) will be used.  In such a case, a sequence of time-stamps
   will protect against forgery.  Each time-stamp needs to be affixed



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   before either the compromise of the signing key or the cracking of
   the algorithms used by the TSA.  TSAs (Time-Stamping Authorities)
   should have long keys (e.g., which at the time of drafting the
   present document was at least 2048 bits for the signing RSA
   algorithm) and/or a "good" or different algorithm.

   Nested time-stamps will also protect the verifier against key
   compromise or cracking the algorithm on the old electronic
   signatures.

   The process will need to be performed and iterated before the
   cryptographic algorithms used for generating the previous time-stamp
   are no longer secure.  Archive validation data may thus bear multiple
   embedded time-stamps.

   This technique is referred to as CAdES-A in the present document.

<span class="h4"><a class="selflink" id="appendix-C.4.6" href="#appendix-C.4.6">C.4.6</a>.  Reference to Additional Data</span>

   Using CAdES-X Type 1 or CAdES-X Type 2 extended validation data,
   verifiers still need to keep track of all the components that were
   used to validate the signature, in order to be able to retrieve them
   again later on.  These components may be archived by an external
   source, like a Trusted Service Provider; in which case, referenced
   information that is provided as part of the ES with Complete
   validation data (CAdES-C) is adequate.  The actual certificates and
   CRL information reference in the CAdES-C can be gathered when needed
   for arbitration.

   If references to additional data are not adequate, then the actual
   values of all the certificates and revocation information required
   may be part of the electronic signature.  This technique is referred
   to as CAdES-X Long Type 1 or CAdES-X Long Type 2 in the present
   document.

<span class="h4"><a class="selflink" id="appendix-C.4.7" href="#appendix-C.4.7">C.4.7</a>.  Time-Stamping for Mutual Recognition</span>

   In some business scenarios, both the signer and the verifier need to
   time-stamp their own copy of the signature value.  Ideally, the two
   time-stamps should be as close as possible to each other.

      EXAMPLE:  A contract is signed by two parties, A and B,
      representing their respective organizations; to time-stamp the
      signer and verifier data, two approaches are possible:

         - under the terms of the contract, a predefined common
           "trusted" TSA may be used;




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         - if both organizations run their own time-stamping services, A
           and B can have the transaction time-stamped by these two
           time-stamping services.

   In the latter case, the electronic signature will only be considered
   valid if both time-stamps were obtained in due time (i.e., there
   should not be a long delay between obtaining the two time-stamps).
   Thus, neither A nor B can repudiate the signing time indicated by
   their own time-stamping service.  Therefore, A and B do not need to
   agree on a common "trusted" TSA to get a valid transaction.

   It is important to note that signatures may be generated "off-line"
   and time-stamped at a later time by anyone, e.g., by the signer or
   any recipient interested in validating the signature.  The time-stamp
   over the signature from the signer can thus be provided by the
   signer, together with the signed document, and/or be obtained by the
   verifier following receipt of the signed document.

   The business scenarios may thus dictate that one or more of the
   long-term signature time-stamping methods described above be used.
   This may be part of a mutually agreed Signature Validation Policy
   that is part of an agreed signature policy under which digital
   signatures may be used to support the business relationship between
   the two parties.

<span class="h4"><a class="selflink" id="appendix-C.4.8" href="#appendix-C.4.8">C.4.8</a>.  TSA Key Compromise</span>

   TSA servers should be built in such a way that once the private
   signature key is installed, there is minimal likelihood of compromise
   over as long as a possible period.  Thus, the validity period for the
   TSA's keys should be as long as possible.

   Both the CAdES-T and the CAdES-C contain at least one time-stamp over
   the signer's signature.  In order to protect against the compromise
   of the private signature key used to produce that time-stamp, the
   Archive validation data can be used when a different Time-Stamping
   Authority key is involved to produce the additional time-stamp.  If
   it is believed that the TSA key used in providing an earlier
   time-stamp may ever be compromised (e.g., outside its validity
   period), then the CAdES-A should be used.  For extremely long
   periods, this may be applied repeatedly using new TSA keys.

   This technique is referred to as a nested CAdES-A in the present
   document.







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<span class="h3"><a class="selflink" id="appendix-C.5" href="#appendix-C.5">C.5</a>.  Multiple Signatures</span>

   Some electronic signatures may only be valid if they bear more than
   one signature.  This is generally the case when a contract is signed
   between two parties.  The ordering of the signatures may or may not
   be important, i.e., one may or may not need to be applied before the
   other.

   Several forms of multiple and counter signatures need to be
   supported, which fall into two basic categories:

      - independent signatures;
      - embedded signatures.

   Independent signatures are parallel signatures where the ordering of
   the signatures is not important.  The capability to have more than
   one independent signature over the same data shall be provided.

   Embedded signatures are applied one after the other and are used
   where the order in which the signatures are applied is important.
   The capability to sign over signed data shall be provided.

   These forms are described in <a href="#section-5.13">Section 5.13</a>.  All other multiple
   signature schemes, e.g., a signed document with a countersignature,
   double countersignatures, or multiple signatures can be reduced to
   one or more occurrences of the above two cases.

Annex D (Informative): Data Protocols to Interoperate with TSPs

<span class="h3"><a class="selflink" id="appendix-D.1" href="#appendix-D.1">D.1</a>.  Operational Protocols</span>

   The following protocols can be used by signers and verifiers to
   interoperate with Trusted Service Providers during the electronic
   signature creation and validation.

<span class="h4"><a class="selflink" id="appendix-D.1.1" href="#appendix-D.1.1">D.1.1</a>.  Certificate Retrieval</span>

   User certificates, CA certificates, and cross-certificates can be
   retrieved from a repository using the Lightweight Directory Access
   Protocol as defined in <a href="./rfc3494">RFC 3494</a> [<a href="./rfc3494" title="&quot;Lightweight Directory Access Protocol version 2 (LDAPv2) to Historic Status&quot;">RFC3494</a>], with the schema defined in
   <a href="./rfc4523">RFC 4523</a> [<a href="./rfc4523" title="&quot;Lightweight Directory Access Protocol (LDAP) Schema Definitions for X.509 Certificates&quot;">RFC4523</a>].

<span class="h4"><a class="selflink" id="appendix-D.1.2" href="#appendix-D.1.2">D.1.2</a>.  CRL Retrieval</span>

   Certificate revocation lists, including authority revocation lists
   and partial CRL variants, can be retrieved from a repository using
   the Lightweight Directory Access Protocol, as defined in <a href="./rfc3494">RFC 3494</a>
   [<a href="./rfc3494" title="&quot;Lightweight Directory Access Protocol version 2 (LDAPv2) to Historic Status&quot;">RFC3494</a>], with the schema defined in <a href="./rfc4523">RFC 4523</a> [<a href="./rfc4523" title="&quot;Lightweight Directory Access Protocol (LDAP) Schema Definitions for X.509 Certificates&quot;">RFC4523</a>].



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<span class="h4"><a class="selflink" id="appendix-D.1.3" href="#appendix-D.1.3">D.1.3</a>.  Online Certificate Status</span>

   As an alternative to the use of certificate revocation lists, the
   status of a certificate can be checked using the Online Certificate
   Status Protocol (OCSP), as defined in <a href="./rfc2560">RFC 2560</a> [<a href="#ref-3" title="&quot;X.509 Internet Public Key Infrastructure Online Certificate Status Protocol - OCSP&quot;">3</a>].

<span class="h4"><a class="selflink" id="appendix-D.1.4" href="#appendix-D.1.4">D.1.4</a>.  Time-Stamping</span>

   The time-stamping service can be accessed using the Time-Stamping
   Protocol defined in <a href="./rfc3161">RFC 3161</a> [<a href="#ref-7" title="&quot;Internet X.509 Public Key Infrastructure Time-Stamp Protocol (TSP)&quot;">7</a>].

<span class="h3"><a class="selflink" id="appendix-D.2" href="#appendix-D.2">D.2</a>.  Management Protocols</span>

   Signers and verifiers can use the following management protocols to
   manage the use of certificates.

<span class="h4"><a class="selflink" id="appendix-D.2.1" href="#appendix-D.2.1">D.2.1</a>.  Request for Certificate Revocation</span>

   Request for a certificate to be revoked can be made using the
   revocation request and response messages defined in <a href="./rfc4210">RFC 4210</a>
   [<a href="./rfc4210" title="&quot;Internet X.509 Public Key Infrastructure Certificate Management Protocol (CMP)&quot;">RFC4210</a>].

Annex E (Informative): Security Considerations

<span class="h3"><a class="selflink" id="appendix-E.1" href="#appendix-E.1">E.1</a>.  Protection of Private Key</span>

   The security of the electronic signature mechanism defined in the
   present document depends on the privacy of the signer's private key.

   Implementations should take steps to ensure that private keys cannot
   be compromised.

<span class="h3"><a class="selflink" id="appendix-E.2" href="#appendix-E.2">E.2</a>.  Choice of Algorithms</span>

   Implementers should be aware that cryptographic algorithms become
   weaker with time.  As new cryptoanalysis techniques are developed and
   computing performance improves, the work factor to break a particular
   cryptographic algorithm will reduce.  Therefore, cryptographic
   algorithm implementations should be modular, allowing new algorithms
   to be readily inserted.  That is, implementers should be prepared for
   the set of mandatory-to-implement algorithms to change over time.










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Annex F (Informative): Example Structured Contents and MIME

<span class="h3"><a class="selflink" id="appendix-F.1" href="#appendix-F.1">F.1</a>.  Use of MIME to Encode Data</span>

   The signed content may be structured using MIME (Multipurpose
   Internet Mail Extensions -- <a href="./rfc2045">RFC 2045</a> [<a href="#ref-6" title="&quot;Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies&quot;">6</a>]).  Whilst the MIME structure
   was initially developed for Internet email, it has a number of
   features that make it useful to provide a common structure for
   encoding a range of electronic documents and other multi-media data
   (e.g., photographs, video).  These features include:

      - providing a means of signalling the type of "object" being
        carried (e.g., text, image, ZIP file, application data);

      - providing a means of associating a file name with an object;

      - associating several independent objects (e.g., a document and
        image) to form a multi-part object;

      - handling  data encoded in text or binary and, if necessary,
        re-encoding the binary as text.

   When encoding a single object, MIME consists of:

      - header information, followed by;

      - encoded content.

   This structure can be extended to support multi-part content.

<span class="h4"><a class="selflink" id="appendix-F.1.1" href="#appendix-F.1.1">F.1.1</a>.  Header Information</span>

   A MIME header includes:

   MIME Version information: e.g., MIME-Version: 1.0

   Content type information, which includes information describing the
   content sufficient for it to be presented to a user or application
   process, as required.  This includes information on the "media type"
   (e.g., text, image, audio) or whether the data is for passing to a
   particular type of application.  In the case of text, the content
   type includes information on the character set used, e.g.,
   Content-Type: text/plain; charset="us-ascii".

   Content-encoding information, which defines how the content is
   encoded (see below about encoding supported by MIME).





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   Other information about the content, such as a description or an
   associated file name.

   An example MIME header for text object is:

   Mime-Version: 1.0
   Content-Type: text/plain; charset=ISO-8859-1
   Content-Transfer-Encoding: quoted-printable

   An example MIME header for a binary file containing a pdf document
   is:

   Content-Type: application/pdf
   Content-Transfer-Encoding: base64
   Content-Description: JCFV201.pdf
   Content-Disposition: filename="JCFV201.pdf"

<span class="h4"><a class="selflink" id="appendix-F.1.2" href="#appendix-F.1.2">F.1.2</a>.  Content Encoding</span>

   MIME supports a range of mechanisms for encoding both text and binary
   data.

   Text data can be carried transparently as lines of text data encoded
   in 7- or 8-bit ASCII characters.  MIME also includes a
   "quoted-printable" encoding that converts characters other than the
   basic ASCII into an ASCII sequence.

   Binary can either be carried:

      - transparently as 8-bit octets; or

      - converted to a basic set of characters using a system called
        Base64.

      NOTE: As there are some mail relays that can only handle 7-bit
      ASCII, Base64 encoding is usually used on the Internet.

<span class="h4"><a class="selflink" id="appendix-F.1.3" href="#appendix-F.1.3">F.1.3</a>.  Multi-Part Content</span>

   Several objects (e.g., text and a file attachment) can be associated
   together using a special "multi-part" content type.  This is
   indicated by the content type "multipart" with an indication of the
   string to be used indicating a separation between each part.

   In addition to a header for the overall multipart content, each part
   includes its own header information indicating the inner content type
   and encoding.




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   An example of a multipart content is:

Mime-Version: 1.0
Content-Type: multipart/mixed; boundary="----
=_NextPart_000_01BC4599.98004A80"
Content-Transfer-Encoding: 7bit

------=_NextPart_000_01BC4599.98004A80
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit

Per your request, I've attached our proposal for the Java Card Version
<span class="h3"><a class="selflink" id="section-2.0" href="#section-2.0">2.0</a> API and the Java Card FAQ.</span>

------=_NextPart_000_01BC4599.98004A80
Content-Type: application/pdf; name="JCFV201.pdf"
Content-Transfer-Encoding: base64
Content-Description: JCFV201.pdf
Content-Disposition: attachment; filename="JCFV201.pdf"

0M8R4KGxGuEAAAAAAAAAAAAAAAAAAAAAPgADAP7/CQAGAAAAAAAAAAAAAAACAAAAAgAAAAA
AAAAAEAAAtAAAAAEAAAD+////AAAAAAMAAAAGAAAA//////////////////////////////
//////////AANhAAQAYg==

------=_NextPart_000_01BC4599.98004A80--

   Multipart content can be nested.  So a set of associated objects
   (e.g., HTML text and images) can be handled as a single attachment to
   another object (e.g., text).

   The Content-Type from each part of the S/MIME message indicates the
   type of content.

<span class="h3"><a class="selflink" id="appendix-F.2" href="#appendix-F.2">F.2</a>.  S/MIME</span>

   The specific use of MIME to carry CMS (extended as defined in the
   present document) secured data is called S/MIME (see [<a href="./rfc3851" title="&quot;Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1 Message Specification&quot;">RFC3851</a>]).

   S/MIME carries electronic signatures as either:

      - an "application/pkcs7-mime" object with the CMS carried as a
        binary attachment (PKCS7 is the name of the early version of
        CMS).

        The signed data may be included in the SignedData, which itself
        may be included in a single S/MIME object.  See <a href="./rfc3851#section-3.4.2">[RFC3851],
        Section&nbsp;3.4.2</a>: "Signing Using application/pkcs7-mime with
        SignedData" and Figure F.1 hereafter.



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   or

      - a "multipart/signed" object with the signed data and the
        signature encoded as separate MIME objects.

        The signed data is not included in the SignedData, and the CMS
        structure only includes the signature.  See [<a href="./rfc3851" title="&quot;Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1 Message Specification&quot;">RFC3851</a>], <a href="#section-3.4.3">Section</a>
        <a href="#section-3.4.3">3.4.3</a>: "Signing Using the multipart/signed Format" and Figure
        F.2 hereafter.

        +-------------++----------++-------------++------------+
        |             ||          ||             ||            |
        |   S/MIME    ||  CAdES   ||    MIME     ||  pdf file  |
        |             ||          ||             ||            |
        |Content-Type=||SignedData||Content-Type=||Dear MrSmith|
        |application/ || eContent ||application/ ||Received    |
        |pkcs7-mime   ||          ||pdf          ||  100 tins  |
        |             ||          ||             ||            |
        |smime-type=  ||     /|   ||       /|    ||  Mr.Jones  |
        |signed-data  ||    / -----+      / ------+            |
        |             ||    \ -----+      \ ------+            |
        |             ||     \|   ||       \|    |+------------+
        |             ||          |+-------------+
        |             |+----------+
        +-------------+

            Figure F.1: Signing Using application/pkcs7-mime

<span class="h4"><a class="selflink" id="appendix-F.2.1" href="#appendix-F.2.1">F.2.1</a>.  Using application/pkcs7-mime</span>

   This approach is similar to handling signed data as any other binary
   file attachment.

   An example of signed data encoded using this approach is:

   Content-Type: application/pkcs7-mime; smime-type=signed-data;
   Content-Transfer-Encoding: base64
   Content-Disposition: attachment; filename=smime.p7m

     567GhIGfHfYT6ghyHhHUujpfyF4f8HHGTrfvhJhjH776tbB9HG4VQbnj7
     77n8HHGT9HG4VQpfyF467GhIGfHfYT6rfvbnj756tbBghyHhHUujhJhjH
     HUujhJh4VQpfyF467GhIGfHfYGTrfvbnjT6jH7756tbB9H7n8HHGghyHh
     6YT64V0GhIGfHfQbnj75








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<span class="h4"><a class="selflink" id="appendix-F.2.2" href="#appendix-F.2.2">F.2.2</a>.  Using application/pkcs7-signature</span>

   CMS also supports an alternative structure where the signature and
   data being protected are separate MIME objects carried within a
   single message.  In this case, the signed data is not included in the
   SignedData, and the CMS structure only includes the signature.  See
   <a href="./rfc3851#section-3.4.3">[RFC3851], Section&nbsp;3.4.3</a>: "Signing Using the multipart/signed Format"
   and Figure F.2 hereafter.

   An example of signed data encoded using this approach is:

   Content-Type: multipart/signed;
             protocol="application/pkcs7-signature";
             micalg=sha1; boundary=boundary42

          --boundary42
          Content-Type: text/plain

          This is a clear-signed message.

          --boundary42

   Content-Type: application/pkcs7-signature; name=smime.p7s
          Content-Transfer-Encoding: base64
          Content-Disposition: attachment; filename=smime.p7s

          ghyHhHUujhJhjH77n8HHGTrfvbnj756tbB9HG4VQpfyF467GhIGfHfYT6
          4VQpfyF467GhIGfHfYT6jH77n8HHGghyHhHUujhJh756tbB9HGTrfvbnj
          n8HHGTrfvhJhjH776tbB9HG4VQbnj7567GhIGfHfYT6ghyHhHUujpfyF4
          7GhIGfHfYT64VQbnj756

          --boundary42--

   With this second approach, the signed data passes through the CMS
   process and is carried as part of a multiple-parts signed MIME
   structure, as illustrated in Figure F.2.  The CMS structure just
   holds the electronic signature.














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   +---------------++----------++-------------++------------+
   |               ||          ||             ||            |
   |     MIME      ||  CAdES   ||    MIME     ||  pdf file  |
   |               ||          ||             ||            |
   |Content-Type=  ||SignedData||Content-Type=||Dear MrSmith|
   |multipart/     ||          ||application/ ||Received    |
   |signed         ||          ||pdf          ||  100 tins  |
   |        /|     ||          ||             ||            |
   |       / -------------------+        /|   ||  Mr.Jones  |
   |       \ -------------------+       / -----+            |
   |        \|     ||          ||       \ -----+            |
   |Content-Type=  ||          ||        \|   |+------------+
   |application/   ||          |+-------------+
   |pdf            ||          |
   |               ||          |
   |Content-Type=  ||          |
   |application/   ||          |
   |pkcs7-signature||          |
   |               ||          |
   |        /|     ||          |
   |       / -------+          |
   |       \ -------+          |
   |        \|     ||----------+
   |               |
   +---------------+

       Figure F.2: Signing Using application/pkcs7-signature

   This second approach (multipart/signed) has the advantage that the
   signed data can be decoded by any MIME-compatible system even if it
   does not recognize CMS-encoded electronic signatures.

Annex G (Informative): Relationship to the European Directive and EESSI

<span class="h3"><a class="selflink" id="appendix-G.1" href="#appendix-G.1">G.1</a>.  Introduction</span>

   This annex provides an indication of the relationship between
   electronic signatures created under the present document and
   requirements under the European Parliament and Council Directive on a
   Community framework for electronic signatures.

      NOTE: Legal advice should be sought on the specific national
      legislation regarding use of electronic signatures.

   The present document is one of a set of standards that has been
   defined under the "European Electronic Signature Standardization
   Initiative" (EESSI) for electronic signature products and solutions
   compliant with the European Directive for Electronic Signatures.



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<span class="h3"><a class="selflink" id="appendix-G.2" href="#appendix-G.2">G.2</a>.  Electronic Signatures and the Directive</span>

   This directive defines electronic signatures as:

      - "data in electronic form which are attached to or logically
        associated with other electronic data and which serve as a
        method of authentication".

   The directive states that an electronic signature should not be
   denied "legal effectiveness and admissibility as evidence in legal
   proceedings" solely on the grounds that it is in electronic form.

   The directive identifies an electronic signature as having
   equivalence to a hand-written signature if it meets specific
   criteria:

      - it is an "advanced electronic signature" with the following
        properties:

         a) it is uniquely linked to the signatory;

         b) it is capable of identifying the signatory;

         c) it is created using means that the signatory can maintain
            under his sole control; and

         d) it is linked to the data to which it relates in such a
            manner that any subsequent change of the data is detectable.

      - it is based on a certificate that meets detailed criteria given
        in Annex I of the directive and is issued by a
        "certification-service-provider" that meets requirements given
        in Annex II of the directive.  Such a certificate is referred to
        as a "qualified certificate";

      - it is created by a "device", for which detailed criteria are
        given in Annex III of the directive.  Such a device is referred
        to a "secure-signature-creation device".

   This form of electronic signature is referred to as a "qualified
   electronic signature" in EESSI (see below).










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<span class="h3"><a class="selflink" id="appendix-G.3" href="#appendix-G.3">G.3</a>.  ETSI Electronic Signature Formats and the Directive</span>

   An electronic signature created in accordance with the present
   document is:

      a) considered to be an "electronic signature" under the terms of
         the Directive;

      b) considered to be an "advanced electronic signature" under the
         terms of the Directive;

      c) considered to be a "Qualified Electronic Signature", provided
         the additional requirements in Annex I, II, and III of the
         Directive are met.  The requirements in Annex I, II, and III of
         the Directive are outside the scope of the present document,
         and are subject to standardization elsewhere.

<span class="h3"><a class="selflink" id="appendix-G.4" href="#appendix-G.4">G.4</a>.  EESSI Standards and Classes of Electronic Signature</span>

<span class="h4"><a class="selflink" id="appendix-G.4.1" href="#appendix-G.4.1">G.4.1</a>.  Structure of EESSI Standardization</span>

   EESSI looks at standards in several areas.  See the ETSI and CEN web
   sites for the latest list of standards and their versions:

      - use of X.509 public key certificates as qualified certificates;

      - security Management and Certificate Policy for CSPs Issuing
        Qualified Certificates;

      - security requirements for trustworthy systems used by CSPs
        Issuing Qualified Certificates;

      - security requirements for Secure Signature Creation Devices;

      - security requirements for Signature Creation Systems;

      - procedures for Electronic Signature Verification;

      - electronic signature syntax and encoding formats;

      - protocol to interoperate with a Time-Stamping Authority;

      - Policy requirements for Time-Stamping Authorities; and

      - XML electronic signature formats.






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   Each of these standards addresses a range of requirements, including
   the requirements of Qualified Electronic Signatures, as specified in
   Article 5.1 of the Directive.  However, some of them also address
   general requirements of electronic signatures for business and
   electronic commerce, which all fall into the category of Article 5.2
   of the Directive.  Such variation in the requirements may be
   identified either as different levels or different options.

<span class="h4"><a class="selflink" id="appendix-G.4.2" href="#appendix-G.4.2">G.4.2</a>.  Classes of Electronic Signatures</span>

   Since some of these standards address a range of requirements, it may
   be useful to identify a set of standards to address a specific
   business need.  Such a set of standards and their uses define a class
   of electronic signature.  The first class already identified is the
   qualified electronic signature, fulfilling the requirements of
   Article 5.1 of the Directive.

   A limited number of "classes of electronic signatures" and
   corresponding profiles could be defined in close cooperation with
   actors on the market (business, users, suppliers). The need for such
   standards is envisaged, in addition to those for qualified electronic
   signatures, in areas such as:

      - different classes of electronic signatures with long-term
        validity;

      - electronic signatures for business transactions with limited
        value.

<span class="h4"><a class="selflink" id="appendix-G.4.3" href="#appendix-G.4.3">G.4.3</a>.  Electronic Signature Classes and the ETSI Electronic Signature</span>
        Format

   The electronic signature format defined in the present document is
   applicable to the EESSI area "electronic signature and encoding
   formats".

   An electronic signature produced by a signer (see <a href="#section-5">Section 5</a> and
   conformance <a href="#section-10.1">Section 10.1</a>) is applicable to the proposed class of
   electronic signature: "qualified electronic signatures fulfilling
   article 5.1".

   With the addition of attributes by the verifier (see <a href="#section-6">Section 6</a> and
   conformance <a href="#section-10.2">Section 10.2</a>) the qualified electronic signature supports
   long-term validity.







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Annex H (Informative): APIs for the Generation and Verification of
                       Electronic Signatures Tokens

   While the present document describes the data format of an electronic
   signature, the question is whether there exist APIs (Application
   Programming Interfaces) able to manipulate these structures.  At
   least two such APIs have been defined; one set by the IETF and
   another set by the OMG (Object Management Group).

<span class="h3"><a class="selflink" id="appendix-H.1" href="#appendix-H.1">H.1</a>.  Data Framing</span>

   In order to be able to use either of these APIs, it will be necessary
   to frame the previously defined electronic signature data structures
   using a mechanism-independent token format.  <a href="./rfc2743#section-3.1">Section&nbsp;3.1 of RFC 2743</a>
   [<a href="./rfc2743" title="&quot;Generic Security Service Application Program Interface Version 2, Update 1&quot;">RFC2743</a>] specifies a mechanism-independent level of encapsulating
   representation for the initial token of a GSS-API context
   establishment sequence, incorporating an identifier of the mechanism
   type to be used on that context and enabling tokens to be interpreted
   unabmiguously.

   In order to be processable by these APIs, all electronic signature
   data formats that are defined in the present document shall be framed
   following that description.

   The encoding format for the token tag is derived from ASN.1 and DER,
   but its concrete representation is defined directly in terms of
   octets rather than at the ASN.1 level, in order to facilitate
   interoperable implementation without use of general ASN.1 processing
   code.  The token tag consists of the following elements, in order:

      1) 0x60 -- Tag for <a href="./rfc2743">RFC 2743</a> SEQUENCE; indicates that constructed
         form, definite length encoding follows.

      2) Token-length octets, specifying length of subsequent data
         (i.e., the summed lengths of elements 3 to 5 in this list, and
         of the mechanism-defined token object following the tag).  This
         element comprises a variable number of octets:

         a) If the indicated value is less than 128, it shall be
            represented in a single octet with bit 8 (high order) set to
            "0" and the remaining bits representing the value.










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         b) If the indicated value is 128 or more, it shall be
            represented in two or more octets, with bit 8 of the first
            octet set to "1" and the remaining bits of the first octet
            specifying the number of additional octets.  The subsequent
            octets carry the value, 8 bits per octet, with the most
            significant digit first.  The minimum number of octets shall
            be used to encode the length (i.e., no octets representing
            leading zeros shall be included within the length encoding).

      3) 0x06 -- Tag for OBJECT IDENTIFIER.

      4) Object identifier length -- length (number of octets) of the
         encoded object identifier contained in element 5, encoded per
         rules as described in 2a) and 2b) above.

      5) object identifier octets -- variable number of octets, encoded
         per ASN.1 BER rules:

         - The first octet contains the sum of two values:

            (1) the top-level object identifier component, multiplied by
                40 (decimal); and

            (2) the second-level object identifier component.

                This special case is the only point within an object
                identifier encoding where a single octet represents
                contents of more than one component.

            - Subsequent octets, if required, encode successively lower
              components in the represented object identifier.  A
              component's encoding may span multiple octets, encoding 7
              bits per octet (most significant bits first) and with bit
              8 set to "1" on all but the final octet in the component's
              encoding.  The minimum number of octets shall be used to
              encode each component (i.e., no octets representing
              leading zeros shall be included within a component's
              encoding).

      NOTE: In many implementations, elements 3 to 5 may be stored and
      referenced as a contiguous string constant.

   The token tag is immediately followed by a mechanism-defined token
   object.  Note that no independent size specifier intervenes following
   the object identifier value to indicate the size of the
   mechanism-defined token object.





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   Tokens conforming to the present document shall have the following
   OID in order to be processable by IDUP-APIs:

   id-etsi-es-IDUP-Mechanism-v1 OBJECT IDENTIFIER ::=
    { itu-t(0) identified-organization(4) etsi(0)
     electronic-signature-standard (1733) part1 (1) IDUPMechanism (4)
     etsiESv1(1) }

<span class="h3"><a class="selflink" id="appendix-H.2" href="#appendix-H.2">H.2</a>.  IDUP-GSS-APIs Defined by the IETF</span>

   The IETF CAT WG produced, in December 1998, an RFC (<a href="./rfc2479">RFC 2479</a>
   [<a href="./rfc2479" title="&quot;Independent Data Unit Protection Generic Security Service Application Program Interface (IDUP- GSS-API)&quot;">RFC2479</a>]) under the name of IDUP-GSS-API (Independent Data Unit
   Protection) able to handle the electronic signature data format
   defined in the present document.

   The IDUP-GSS-API includes support for non-repudiation services.

   It supports evidence generation, where "evidence" is information that
   either by itself, or when used in conjunction with other information,
   is used to establish proof about an event or action, as well as
   evidence verification.

   IDUP supports various types of evidences.  All the types defined in
   IDUP are supported in the present document through the
   commitment-type parameter.

   <a href="#section-2.3.3">Section 2.3.3</a> of IDUP describes the specific calls needed to handle
   evidence ("EV" calls).  The "EV" group of calls provides a simple,
   high-level interface to underlying IDUP mechanisms when application
   developers need to deal with only evidence: not with encryption or
   integrity services.

   All generations and verification are performed according to the
   content of a NR policy that is referenced in the context.

   Get_token_details is used to return the attributes that correspond to
   a given input token to an application.  Since IDUP-GSS-API tokens are
   meant to be opaque to the calling application, this function allows
   the application to determine information about the token without
   having to violate the opaqueness intention of IDUP.  Of primary
   importance is the mechanism type, which the application can then use
   as input to the IDUP_Establish_Env() call in order to establish the
   correct environment in which to have the token processed.

   Generate_token generates a non-repudiation token using the current
   environment.





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   Verify_evidence verifies the evidence token using the current
   environment.  This operation returns a major_status code that can be
   used to determine whether the evidence contained in a token is
   complete (i.e., can be successfully verified (perhaps years) later).
   If a token's evidence is not complete, the token can be passed to
   another API, form_complete_pidu, to complete it.  This happens when a
   status "conditionally valid" is returned.  That status corresponds to
   the status "validation incomplete" of the present document.

   Form_complete_PIDU is used primarily when the evidence token itself
   does not contain all the data required for its verification, and it
   is anticipated that some of the data not stored in the token may
   become unavailable during the interval between generation of the
   evidence token and verification unless it is stored in the token.
   The Form_Complete_PIDU operation gathers the missing information and
   includes it in the token so that verification can be guaranteed to be
   possible at any future time.

<span class="h3"><a class="selflink" id="appendix-H.3" href="#appendix-H.3">H.3</a>.  CORBA Security Interfaces Defined by the OMG</span>

   Non-repudiation interfaces have been defined in "CORBA Security", a
   document produced by the OMG (Object Management Group).  These
   interfaces are described in IDL (Interface Definition Language) and
   are optional.

   The handling of "tokens" supporting non-repudiation is done through
   the following interfaces:

      - set_NR_features specifies the features to apply to future
        evidence generation and verification operations;

      - get_NR_features returns the features that will be applied to
        future evidence generation and verification operations;

      - generate_token generates a non-repudiation token using the
        current non-repudiation features;

      - verify_evidence verifies the evidence token using the current
        non-repudiation features;

      - get_tokens_details returns information about an input
        non-repudiation token.  The information returned depends upon
        the type of token;

      - form_complete_evidence is used when the evidence token itself
        does not contain all the data required for its verification, and
        it is anticipated that some of the data not stored in the token
        may become unavailable during the interval between generation of



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        the evidence token and verification unless it is stored in the
        token.  The form_complete_evidence operation gathers the missing
        information and includes it in the token so that verification
        can be guaranteed to be possible at any future time.

      NOTE: The similarity between the two sets of APIs is noticeable.

Annex I (Informative): Cryptographic Algorithms

   <a href="./rfc3370">RFC 3370</a> [<a href="#ref-10" title="&quot;Cryptographic Message Syntax (CMS) Algorithms&quot;">10</a>] describes the conventions for using several
   cryptographic algorithms with the Crytographic Message Syntax (CMS).
   Only the hashing and signing algorithms are appropriate for use with
   the present document.

   Since the publication of <a href="./rfc3370">RFC 3370</a> [<a href="#ref-10" title="&quot;Cryptographic Message Syntax (CMS) Algorithms&quot;">10</a>], MD5 has been broken.  This
   algorithm is no longer considered appropriate and has been deleted
   from the list of algorithms.

<span class="h3"><a class="selflink" id="appendix-I.1" href="#appendix-I.1">I.1</a>.  Digest Algorithms</span>

<span class="h4"><a class="selflink" id="appendix-I.1.1" href="#appendix-I.1.1">I.1.1</a>.  SHA-1</span>

   The SHA-1 digest algorithm is defined in FIPS Pub 180-1.  The
   algorithm identifier for SHA-1 is:

sha-1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3) oiw(14)
secsig(3) algorithm(2) 26 }

   The AlgorithmIdentifier parameters field is optional.  If present,
   the parameters field shall contain an ASN.1 NULL.  Implementations
   should accept SHA-1 AlgorithmIdentifiers with absent parameters as
   well as NULL parameters.  Implementations should generate SHA-1
   AlgorithmIdentifiers with NULL parameters.

<span class="h4"><a class="selflink" id="appendix-I.1.2" href="#appendix-I.1.2">I.1.2</a>.  General</span>

   The following is a selection of work that has been done in the area
   of digest algorithms or, as they are often called, hash functions:

      - ISO/IEC 10118-1 (1994) [<a href="#ref-ISO10118-1" title="&quot;Information technology - Security techniques - Hash-functions - Part 1: General&quot;">ISO10118-1</a>]: "Information technology -
        Security techniques - Hash-functions - Part 1: General". ISO/IEC
        10118-1 contains definitions and describes basic concepts.

      - ISO/IEC 10118-2 (1994) [<a href="#ref-ISO10118-2" title="&quot;Information technology - Security techniques - Hash-functions - Part 2: Hash-functions using an n-bit block cipher algorithm&quot;">ISO10118-2</a>]: "Information technology -
        Security techniques - Hash-functions - Part 2: Hash-functions
        using an n-bit block cipher algorithm".  ISO/IEC 10118-2
        specifies two ways to construct a hash-function from a block
        cipher.



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      - ISO/IEC 10118-3 (1997) [<a href="#ref-ISO10118-3" title="&quot;Information technology - Security techniques - Hash-functions - Part 3: Dedicated hash-functions&quot;">ISO10118-3</a>]: "Information technology -
        Security techniques - Hash-functions - Part 3: Dedicated
        hash-functions".  ISO/IEC 10118-3 specifies the following
        dedicated hash-functions:

         - SHA-1 (FIPS 180-1);
         - RIPEMD-128;
         - RIPEMD-160.

      - ISO/IEC 10118-4 (1998) [<a href="#ref-ISO10118-4" title="&quot;Information technology - Security techniques - Hash-functions - Part 4: Hash- functions using modular arithmetic&quot;">ISO10118-4</a>]: "Information technology -
        Security techniques - Hash-functions - Part 4: Hash-functions
        using modular arithmetic".

      - <a href="./rfc1320">RFC 1320</a> (PS 1992): "The MD4 Message-Digest Algorithm".  <a href="./rfc1320">RFC</a>
        <a href="./rfc1320">1320</a> specifies the hash-function MD4.  Today, MD4 is considered
        outdated.

      - <a href="./rfc1321">RFC 1321</a> (I 1992): "The MD5 Message-Digest Algorithm".  <a href="./rfc1321">RFC 1321</a>
        (informational) specifies the hash-function MD5.  Today, MD5 is
        not recommended for new implementations.

      - FIPS Publication 180-1 (1995): "Secure Hash Standard".  FIPS
        180-1 specifies the Secure Hash Algorithm (SHA), dedicated hash-
        function developed for use with the DSA.  The original SHA,
        published in 1993, was slightly revised in 1995 and renamed
        SHA-1.

      - ANSI X9.30-2 (1997) [<a href="#ref-X9.30-2" title="&quot;Public Key Cryptography for the Financial Services Industry - Part 2: The Secure Hash Algorithm (SHA-1)&quot;">X9.30-2</a>]: "Public Key Cryptography for the
        Financial Services Industry - Part 2: The Secure Hash Algorithm
        (SHA-1)".  X9.30-2 specifies the ANSI-Version of SHA-1.

      - ANSI X9.31-2 (1996) [<a href="#ref-X9.31-2" title="&quot;Public Key Cryptography Using Reversible Algorithms for the Financial Services Industry - Part 2: Hash Algorithms&quot;">X9.31-2</a>]: "Public Key Cryptography Using
        Reversible Algorithms for the Financial Services Industry - Part
        2: Hash Algorithms".  X9.31-2 specifies hash algorithms.

<span class="h3"><a class="selflink" id="appendix-I.2" href="#appendix-I.2">I.2</a>.  Digital Signature Algorithms</span>

<span class="h4"><a class="selflink" id="appendix-I.2.1" href="#appendix-I.2.1">I.2.1</a>.  DSA</span>

   The DSA signature algorithm is defined in FIPS Pub 186.  DSA is
   always used with the SHA-1 message digest algorithm.  The algorithm
   identifier for DSA is:

id-dsa-with-sha1 OBJECT IDENTIFIER ::=  { iso(1) member-body(2) us(840)
x9-57 (10040) x9cm(4) 3 }

   The AlgorithmIdentifier parameters field shall not be present.




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<span class="h4"><a class="selflink" id="appendix-I.2.2" href="#appendix-I.2.2">I.2.2</a>.  RSA</span>

   The RSA signature algorithm is defined in <a href="./rfc3447">RFC 3447</a> [<a href="./rfc3447" title="&quot;Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1&quot;">RFC3447</a>].  <a href="./rfc3370">RFC</a>
   <a href="./rfc3370">3370</a> [<a href="#ref-10" title="&quot;Cryptographic Message Syntax (CMS) Algorithms&quot;">10</a>] specifies the use of the RSA signature algorithm with the
   SHA-1 algorithm.  The algorithm identifier for RSA with SHA-1 is:

   Sha1WithRSAEncryption OBJECT IDENTIFIER ::= { iso(1) member-body(2)
   us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 5 }

      NOTE: <a href="./rfc3370">RFC 3370</a> [<a href="#ref-10" title="&quot;Cryptographic Message Syntax (CMS) Algorithms&quot;">10</a>] recommends that MD5 not be used for new
      implementations.

<span class="h4"><a class="selflink" id="appendix-I.2.3" href="#appendix-I.2.3">I.2.3</a>.  General</span>

      The following is a selection of work that has been done in the
      area of digital signature mechanisms:

      - FIPS Publication 186 (1994): "Digital Signature Standard".
        NIST's Digital Signature Algorithm (DSA) is a variant of
        ElGamal's Discrete Logarithm-based digital signature mechanism.
        The DSA requires a 160-bit hash-function and mandates SHA-1.

      - IEEE P1363 (2000) [<a href="#ref-P1363" title="&quot;Standard Specifications for Public-Key Cryptography&quot;">P1363</a>]: "Standard Specifications for Public-
        Key Cryptography".  IEEE P1363 contains mechanisms for digital
        signatures, key establishment, and encipherment based on three
        families of public key schemes:

      - "Conventional" Discrete Logarithm (DL)-based techniques, i.e.,
        Diffie-Hellman (DH) key agreement, Menezes-Qu-Vanstone (MQV) key
        agreement, the Digital Signature Algorithm (DSA), and
        Nyberg-Rueppel (NR) digital signatures;

      - Elliptic Curve (EC)-based variants of the DL-mechanisms
        specified above, i.e., EC-DH, EC-MQV, EC-DSA, and EC-NR.  For
        elliptic curves, implementation options include mod p and
        characteristic 2 with polynomial or normal basis representation;

      - Integer Factoring (IF)-based techniques, including RSA
        encryption, RSA digital signatures, and RSA-based key transport.

      - ISO/IEC 9796-2 (1997) [<a href="#ref-ISO9796-2" title="&quot;Information technology - Security techniques - Digital signature schemes giving message recovery - Part 2: Integer factorization based mechanisms&quot;">ISO9796-2</a>]: "Information technology -
        Security techniques - Digital signature schemes giving message
        recovery - Part 2: Mechanisms using a hash-function".  ISO/IEC
        9796-2 specifies digital signature mechanisms with partial
        message recovery that are also based on the RSA technique but
        make use of a hash-function.





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      - ISO/IEC 9796-4 (1998) [<a href="#ref-ISO9796-4" title="&quot;Digital signature schemes giving message recovery - Part 4: Discrete logarithm based mechanisms&quot;">ISO9796-4</a>]: "Digital signature schemes
        giving message recovery - Part 4: Discrete logarithm based
        mechanisms".  ISO/IEC 9796-4 specifies digital signature
        mechanisms with partial message recovery that are based on
        Discrete Logarithm techniques.  The document includes the
        Nyberg-Rueppel scheme.

      - ISO/IEC 14888-1 [<a href="#ref-ISO14888-1" title="">ISO14888-1</a>]: "Digital signatures with appendix
        - Part 1: General".  ISO/IEC 14888-1 contains definitions and
        describes the basic concepts of digital signatures with
        appendix.

      - ISO/IEC 14888-2 [<a href="#ref-ISO14888-2" title="">ISO14888-2</a>]: "Digital signatures with appendix
        - Part 2: Identity-based mechanisms".  ISO/IEC 14888-2 specifies
        digital signature schemes with appendix that make use of
        identity-based keying material.  The document includes the
        zero-knowledge techniques of Fiat-Shamir and Guillou-Quisquater.

      - ISO/IEC 14888-3 [<a href="#ref-ISO14888-3" title="">ISO14888-3</a>]: "Digital signatures with appendix
        - Part 3: Certificate-based mechanisms".  ISO/IEC 14888-3
        specifies digital signature schemes with appendix that make use
        of certificate-based keying material.  The document includes
        five schemes:

         - DSA;
         - EC-DSA, an elliptic curve-based analog of NIST's Digital
           Signature Algorithm;
         - Pointcheval-Vaudeney signatures;
         - RSA signatures;
         - ESIGN.

      - ISO/IEC 15946-2 (2002) [<a href="#ref-ISO15946-2" title="&quot;Information technology - Security techniques - Cryptographic techniques based on elliptic curves - Part 2: Digital signatures&quot;">ISO15946-2</a>]: "Cryptographic techniques
        based on elliptic curves - Part 2: Digital signatures",
        specifies digital signature schemes with appendix using elliptic
        curves.

      - The document includes two schemes:

        - EC-DSA, an elliptic curve-based analog of NIST's Digital
          Signature Algorithm;

        - EC-AMV, an elliptic curve-based analog of the Agnew-Muller-
          Vanstone signature algorithm.








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      - ANSI X9.31-1 (1997) [<a href="#ref-X9.31-1" title="&quot;Public Key Cryptography Using Reversible Algorithms for the Financial Services Industry - Part 1: The RSA Signature Algorithm&quot;">X9.31-1</a>]: "Public Key Cryptography Using
        Reversible Algorithms for the Financial Services Industry - Part
        1: The RSA Signature Algorithm".  ANSI X9.31-1 specifies a
        digital signature mechanism with appendix using the RSA public
        key technique.

      - ANSI X9.30-1 (1997) [<a href="#ref-X9.30-1" title="&quot;Public Key Cryptography for the Financial Services Industry - Part 1: The Digital Signature Algorithm (DSA)&quot;">X9.30-1</a>]: "Public Key Cryptography Using
        Irreversible Algorithms for the Financial Services Industry -
        Part 1: The Digital Signature Algorithm (DSA)".  ANSI X9.30-1
        specifies the DSA, NIST's Digital Signature Algorithm.

      - ANSI X9.62 (1998) [<a href="#ref-X9.62" title="&quot;Public Key Cryptography for the Financial Services Industry - The Elliptic Curve Digital Signature Algorithm (ECDSA)&quot;">X9.62</a>]: "Public Key Cryptography for the
        Financial Services Industry - The Elliptic Curve Digital
        Signature Algorithm (ECDSA)".  ANSI X9.62 specifies the Elliptic
        Curve Digital Signature Algorithm, an analog of NIST's Digital
        Signature Algorithm (DSA) using elliptic curves.  The appendices
        provide tutorial information on the underlying mathematics for
        elliptic curve cryptography and give many examples.

Annex J (Informative): Guidance on Naming

<span class="h3"><a class="selflink" id="appendix-J.1" href="#appendix-J.1">J.1</a>.  Allocation of Names</span>

   The subject name shall be allocated through a registration scheme
   administered through a Registration Authority (RA) to ensure
   uniqueness.  This RA may be an independent body or a function carried
   out by the Certification Authority.

   In addition to ensuring uniqueness, the RA shall verify that the name
   allocated properly identifies the applicant and that authentication
   checks are carried out to protect against masquerade.

   The name allocated by an RA is based on registration information
   provided by, or relating to, the applicant (e.g., his personal name,
   date of birth, residence address) and information allocated by the
   RA. Three variations commonly exist:

      - the name is based entirely on registration information, which
        uniquely identifies the applicant (e.g., "Pierre Durand (born
        on) July 6, 1956");

      - the name is based on registration information, with the addition
        of qualifiers added by the registration authority to ensure
        uniqueness (e.g., "Pierre Durand 12");

      - the registration information is kept private by the registration
        authority and the registration authority allocates a
        "pseudonym".



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<span class="h3"><a class="selflink" id="appendix-J.2" href="#appendix-J.2">J.2</a>.  Providing Access to Registration Information</span>

   Under certain circumstances, it may be necessary for information used
   during registration, but not published in the certificate, to be made
   available to third parties (e.g., to an arbitrator to resolve a
   dispute or for law enforcement).  This registration information is
   likely to include personal and sensitive information.

   Thus, the RA needs to establish a policy for:

         - whether the registration information should be disclosed;
         - to whom such information should be disclosed;
         - under what circumstances such information should be
           disclosed.

   This policy may be different whether the RA is being used only within
   a company or for public use.  The policy will have to take into
   account national legislation and in particular any data protection
   and privacy legislation.

   Currently, the provision of access to registration is a local matter
   for the RA.  However, if open access is required, standard protocols,
   such as HTTP -- <a href="./rfc2068">RFC 2068</a> (Internet Web Access Protocol), may be
   employed with the addition of security mechanisms necessary to meet
   the data protection requirements (e.g., Transport Layer Security --
   <a href="./rfc4346">RFC 4346</a> [<a href="./rfc4346" title="&quot;The Transport Layer Security (TLS) Protocol Version 1.1&quot;">RFC4346</a>]) with client authentication.

<span class="h3"><a class="selflink" id="appendix-J.3" href="#appendix-J.3">J.3</a>.  Naming Schemes</span>

<span class="h4"><a class="selflink" id="appendix-J.3.1" href="#appendix-J.3.1">J.3.1</a>.  Naming Schemes for Individual Citizens</span>

   In some cases, the subject name that is contained in a public key
   certificate may not be meaningful enough.  This may happen because of
   the existence of homonyms or because of the use of pseudonyms.  A
   distinction could be made if more attributes were present.  However,
   adding more attributes to a public key certificate placed in a public
   repository would be going against the privacy protection
   requirements.

   In any case, the Registration Authority will get information at the
   time of registration, but not all that information will be placed in
   the certificate.  In order to achieve a balance between these two
   opposite requirements, the hash values of some additional attributes
   can be placed in a public key certificate.  When the certificate
   owner provides these additional attributes, then they can be
   verified.  Using biometrics attributes may unambiguously identify a
   person.  Examples of biometrics attributes that can be used include:
   a picture or a manual signature from the certificate owner.



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      NOTE: Using hash values protects privacy only if the possible
      inputs are large enough.  For example, using the hash of a
      person's social security number is generally not sufficient since
      it can easily be reversed.

   A picture can be used if the verifier once met the person and later
   on wants to verify that the certificate that he or she got relates to
   the person whom was met.  In such a case, at the first exchange, the
   picture is sent, and the hash contained in the certificate may be
   used by the verifier to verify that it is the right person.  At the
   next exchange, the picture does not need to be sent again.

   A manual signature may be used if a signed document has been received
   beforehand.  In such a case, at the first exchange, the drawing of
   the manual signature is sent, and the hash contained in the
   certificate may be used by the verifier to verify that it is the
   right manual signature.  At the next exchange, the manual signature
   does not need to be sent again.

<span class="h4"><a class="selflink" id="appendix-J.3.2" href="#appendix-J.3.2">J.3.2</a>.  Naming Schemes for Employees of an Organization</span>

   The name of an employee within an organization is likely to be some
   combination of the name of the organization and the identifier of the
   employee within that organization.

   An organization name is usually a registered name, i.e., business or
   trading name used in day-to-day business.  This name is registered by
   a Naming Authority, which guarantees that the organization's
   registered name is unambiguous and cannot be confused with another
   organization.

   In order to get more information about a given registered
   organization name, it is necessary to go back to a publicly available
   directory maintained by the Naming Authority.

   The identifier may be a name or a pseudonym (e.g., a nickname or an
   employee number).  When it is a name, it is supposed to be
   descriptive enough to unambiguously identify the person.  When it is
   a pseudonym, the certificate does not disclose the identity of the
   person.  However, it ensures that the person has been correctly
   authenticated at the time of registration and therefore may be
   eligible to some advantages implicitly or explicitly obtained through
   the possession of the certificate.  In either case, however, this can
   be insufficient because of the existence of homonyms.

   Placing more attributes in the certificate may be one solution, for
   example, by giving the organization unit of the person or the name of
   a city where the office is located.  However, the more information is



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   placed in the certificate, the more problems arise if there is a
   change in the organization structure or the place of work.  So this
   may not be the best solution.  An alternative is to provide more
   attributes (like the organization unit and the place of work) through
   access to a directory maintained by the company.  It is likely that,
   at the time of registration, the Registration Authority got more
   information than what was placed in the certificate, if such
   additional information is placed in a repository accessible only to
   the organization.

Acknowledgments

   Special thanks to Russ Housley for reviewing the document.

Authors' Addresses

   Denis Pinkas
   Bull SAS
   Rue Jean-Jaures
   78340 Les Clayes sous Bois CEDEX
   FRANCE
   EMail: Denis.Pinkas@bull.net

   Nick Pope
   Thales eSecurity
   Meadow View House
   Long Crendon
   Aylesbury
   Buck
   HP18 9EQ
   United Kingdom
   EMail: nick.pope@thales-esecurity.com

   John Ross
   Security &amp; Standards Consultancy Ltd
   The Waterhouse Business Centre
   2 Cromer Way
   Chelmsford
   Essex
   CM1 2QE
   United Kingdom
   EMail: ross@secstan.com









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Full Copyright Statement

   Copyright (C) The IETF Trust (2008).

   This document is subject to the rights, licenses and restrictions
   contained in <a href="https://www.rfc-editor.org/bcp/bcp78">BCP 78</a>, and except as set forth therein, the authors
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   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
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   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Intellectual Property

   The IETF takes no position regarding the validity or scope of any
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   Copies of IPR disclosures made to the IETF Secretariat and any
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   The IETF invites any interested party to bring to its attention any
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