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<pre>Network Working Group                                          S. Turner
Request for Comments: 5275                                          IECA
Category: Standards Track                                      June 2008


             <span class="h1">CMS Symmetric Key Management and Distribution</span>

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   This document describes a mechanism to manage (i.e., set up,
   distribute, and rekey) keys used with symmetric cryptographic
   algorithms.  Also defined herein is a mechanism to organize users
   into groups to support distribution of encrypted content using
   symmetric cryptographic algorithms.  The mechanism uses the
   Cryptographic Message Syntax (CMS) protocol and Certificate
   Management over CMS (CMC) protocol to manage the symmetric keys.  Any
   member of the group can then later use this distributed shared key to
   decrypt other CMS encrypted objects with the symmetric key.  This
   mechanism has been developed to support Secure/Multipurpose Internet
   Mail Extensions (S/MIME) Mail List Agents (MLAs).























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Table of Contents

   <a href="#section-1">1</a>. Introduction ....................................................<a href="#page-4">4</a>
      <a href="#section-1.1">1.1</a>. Conventions Used in This Document ..........................<a href="#page-4">4</a>
      <a href="#section-1.2">1.2</a>. Applicability to E-mail ....................................<a href="#page-5">5</a>
      <a href="#section-1.3">1.3</a>. Applicability to Repositories ..............................<a href="#page-5">5</a>
      <a href="#section-1.4">1.4</a>. Using the Group Key ........................................<a href="#page-5">5</a>
   <a href="#section-2">2</a>. Architecture ....................................................<a href="#page-6">6</a>
   <a href="#section-3">3</a>. Protocol Interactions ...........................................<a href="#page-7">7</a>
      <a href="#section-3.1">3.1</a>. Control Attributes .........................................<a href="#page-8">8</a>
           <a href="#section-3.1.1">3.1.1</a>. GL Use KEK .........................................<a href="#page-10">10</a>
           <a href="#section-3.1.2">3.1.2</a>. Delete GL ..........................................<a href="#page-14">14</a>
           <a href="#section-3.1.3">3.1.3</a>. Add GL Member ......................................<a href="#page-14">14</a>
           <a href="#section-3.1.4">3.1.4</a>. Delete GL Member ...................................<a href="#page-15">15</a>
           <a href="#section-3.1.5">3.1.5</a>. Rekey GL ...........................................<a href="#page-16">16</a>
           <a href="#section-3.1.6">3.1.6</a>. Add GL Owner .......................................<a href="#page-16">16</a>
           <a href="#section-3.1.7">3.1.7</a>. Remove GL Owner ....................................<a href="#page-17">17</a>
           <a href="#section-3.1.8">3.1.8</a>. GL Key Compromise ..................................<a href="#page-17">17</a>
           <a href="#section-3.1.9">3.1.9</a>. GL Key Refresh .....................................<a href="#page-18">18</a>
           <a href="#section-3.1.10">3.1.10</a>. GLA Query Request and Response ....................<a href="#page-18">18</a>
                  <a href="#section-3.1.10.1">3.1.10.1</a>. GLA Query Request ........................<a href="#page-18">18</a>
                  <a href="#section-3.1.10.2">3.1.10.2</a>. GLA Query Response .......................<a href="#page-19">19</a>
                  <a href="#section-3.1.10.3">3.1.10.3</a>. Request and Response Types ...............<a href="#page-19">19</a>
           <a href="#section-3.1.11">3.1.11</a>. Provide Cert ......................................<a href="#page-19">19</a>
           <a href="#section-3.1.12">3.1.12</a>. Update Cert .......................................<a href="#page-20">20</a>
           <a href="#section-3.1.13">3.1.13</a>. GL Key ............................................<a href="#page-21">21</a>
      <a href="#section-3.2">3.2</a>. Use of CMC, CMS, and PKIX .................................<a href="#page-23">23</a>
           <a href="#section-3.2.1">3.2.1</a>. Protection Layers ..................................<a href="#page-23">23</a>
                  <a href="#section-3.2.1.1">3.2.1.1</a>. Minimum Protection ........................<a href="#page-23">23</a>
                  <a href="#section-3.2.1.2">3.2.1.2</a>. Additional Protection .....................<a href="#page-24">24</a>
           <a href="#section-3.2.2">3.2.2</a>. Combining Requests and Responses ...................<a href="#page-24">24</a>
           <a href="#section-3.2.3">3.2.3</a>. GLA Generated Messages .............................<a href="#page-26">26</a>
           <a href="#section-3.2.4">3.2.4</a>. CMC Control Attributes and CMS Signed Attributes ...<a href="#page-27">27</a>
                  <a href="#section-3.2.4.1">3.2.4.1</a>. Using cMCStatusInfoExt ....................<a href="#page-27">27</a>
                  <a href="#section-3.2.4.2">3.2.4.2</a>. Using transactionId .......................<a href="#page-30">30</a>
                  <a href="#section-3.2.4.3">3.2.4.3</a>. Using Nonces and signingTime ..............<a href="#page-30">30</a>
                  3.2.4.4. CMC and CMS Attribute Support
                           Requirements ..............................<a href="#page-31">31</a>
           <a href="#section-3.2.5">3.2.5</a>. Resubmitted GL Member Messages .....................<a href="#page-31">31</a>
           <a href="#section-3.2.6">3.2.6</a>. PKIX Certificate and CRL Profile ...................<a href="#page-31">31</a>
   <a href="#section-4">4</a>. Administrative Messages ........................................<a href="#page-32">32</a>
      <a href="#section-4.1">4.1</a>. Assign KEK to GL ..........................................<a href="#page-32">32</a>
      <a href="#section-4.2">4.2</a>. Delete GL from GLA ........................................<a href="#page-36">36</a>
      <a href="#section-4.3">4.3</a>. Add Members to GL .........................................<a href="#page-38">38</a>
           <a href="#section-4.3.1">4.3.1</a>. GLO Initiated Additions ............................<a href="#page-39">39</a>
           <a href="#section-4.3.2">4.3.2</a>. Prospective Member Initiated Additions .............<a href="#page-47">47</a>
      <a href="#section-4.4">4.4</a>. Delete Members from GL ....................................<a href="#page-49">49</a>
           <a href="#section-4.4.1">4.4.1</a>. GLO Initiated Deletions ............................<a href="#page-50">50</a>



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           <a href="#section-4.4.2">4.4.2</a>. Member Initiated Deletions .........................<a href="#page-56">56</a>
      <a href="#section-4.5">4.5</a>. Request Rekey of GL .......................................<a href="#page-57">57</a>
           <a href="#section-4.5.1">4.5.1</a>. GLO Initiated Rekey Requests .......................<a href="#page-59">59</a>
           <a href="#section-4.5.2">4.5.2</a>. GLA Initiated Rekey Requests .......................<a href="#page-62">62</a>
      <a href="#section-4.6">4.6</a>. Change GLO ................................................<a href="#page-63">63</a>
      <a href="#section-4.7">4.7</a>. Indicate KEK Compromise ...................................<a href="#page-65">65</a>
           <a href="#section-4.7.1">4.7.1</a>. GL Member Initiated KEK Compromise Message .........<a href="#page-66">66</a>
           <a href="#section-4.7.2">4.7.2</a>. GLO Initiated KEK Compromise Message ...............<a href="#page-67">67</a>
      <a href="#section-4.8">4.8</a>. Request KEK Refresh .......................................<a href="#page-69">69</a>
      <a href="#section-4.9">4.9</a>. GLA Query Request and Response ............................<a href="#page-70">70</a>
      <a href="#section-4.10">4.10</a>. Update Member Certificate ................................<a href="#page-73">73</a>
           <a href="#section-4.10.1">4.10.1</a>. GLO and GLA Initiated Update Member Certificate ...<a href="#page-73">73</a>
           <a href="#section-4.10.2">4.10.2</a>. GL Member Initiated Update Member Certificate .....<a href="#page-75">75</a>
   <a href="#section-5">5</a>. Distribution Message ...........................................<a href="#page-77">77</a>
      <a href="#section-5.1">5.1</a>. Distribution Process ......................................<a href="#page-78">78</a>
   <a href="#section-6">6</a>. Algorithms .....................................................<a href="#page-79">79</a>
      <a href="#section-6.1">6.1</a>. KEK Generation Algorithm ..................................<a href="#page-79">79</a>
      <a href="#section-6.2">6.2</a>. Shared KEK Wrap Algorithm .................................<a href="#page-79">79</a>
      <a href="#section-6.3">6.3</a>. Shared KEK Algorithm ......................................<a href="#page-79">79</a>
   <a href="#section-7">7</a>. Message Transport ..............................................<a href="#page-80">80</a>
   <a href="#section-8">8</a>. Security Considerations ........................................<a href="#page-80">80</a>
   <a href="#section-9">9</a>. Acknowledgements ...............................................<a href="#page-81">81</a>
   <a href="#section-10">10</a>. References ....................................................<a href="#page-81">81</a>
      <a href="#section-10.1">10.1</a>. Normative References .....................................<a href="#page-81">81</a>
      <a href="#section-10.2">10.2</a>. Informative References ...................................<a href="#page-82">82</a>
   <a href="#appendix-A">Appendix A</a>. ASN.1 Module ..........................................<a href="#page-83">83</a>

























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

   With the ever-expanding use of secure electronic communications
   (e.g., S/MIME [<a href="#ref-MSG" title="&quot;Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1 Message Specification&quot;">MSG</a>]), users require a mechanism to distribute
   encrypted data to multiple recipients (i.e., a group of users).
   There are essentially two ways to encrypt the data for recipients:
   using asymmetric algorithms with public key certificates (PKCs) or
   symmetric algorithms with symmetric keys.

   With asymmetric algorithms, the originator forms an originator-
   determined content-encryption key (CEK) and encrypts the content,
   using a symmetric algorithm.  Then, using an asymmetric algorithm and
   the recipient's PKCs, the originator generates per-recipient
   information that either (a) encrypts the CEK for a particular
   recipient (ktri RecipientInfo CHOICE) or (b) transfers sufficient
   parameters to enable a particular recipient to independently generate
   the same KEK (kari RecipientInfo CHOICE).  If the group is large,
   processing of the per-recipient information may take quite some time,
   not to mention the time required to collect and validate the PKCs for
   each of the recipients.  Each recipient identifies its per-recipient
   information and uses the private key associated with the public key
   of its PKC to decrypt the CEK and hence gain access to the encrypted
   content.

   With symmetric algorithms, the origination process is slightly
   different.  Instead of using PKCs, the originator uses a previously
   distributed secret key-encryption key (KEK) to encrypt the CEK (kekri
   RecipientInfo CHOICE).  Only one copy of the encrypted CEK is
   required because all the recipients already have the shared KEK
   needed to decrypt the CEK and hence gain access to the encrypted
   content.

   The techniques to protect the shared KEK are beyond the scope of this
   document.  Only the members of the list and the key manager should
   have the KEK in order to maintain confidentiality.  Access control to
   the information protected by the KEK is determined by the entity that
   encrypts the information, as all members of the group have access.
   If the entity performing the encryption wants to ensure that some
   subset of the group does not gain access to the information, either a
   different KEK should be used (shared only with this smaller group) or
   asymmetric algorithms should be used.

<span class="h3"><a class="selflink" id="section-1.1" href="#section-1.1">1.1</a>.  Conventions Used in This Document</span>

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in <a href="https://www.rfc-editor.org/bcp/bcp14">BCP 14</a>, <a href="./rfc2119">RFC 2119</a>
   [<a href="./rfc2119" title="&quot;Key words for use in RFCs to Indicate Requirement Levels&quot;">RFC2119</a>].



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<span class="h3"><a class="selflink" id="section-1.2" href="#section-1.2">1.2</a>.  Applicability to E-mail</span>

   One primary audience for this distribution mechanism is e-mail.
   Distribution lists, sometimes referred to as mail lists, support the
   distribution of messages to recipients subscribed to the mail list.
   There are two models for how the mail list can be used.  If the
   originator is a member of the mail list, the originator sends
   messages encrypted with the shared KEK to the mail list (e.g.,
   listserv or majordomo) and the message is distributed to the mail
   list members.  If the originator is not a member of the mail list
   (does not have the shared KEK), the originator sends the message
   (encrypted for the MLA) to the Mail List Agent (MLA), and then the
   MLA uses the shared KEK to encrypt the message for the members.  In
   either case, the recipients of the mail list use the previously
   distributed-shared KEK to decrypt the message.

<span class="h3"><a class="selflink" id="section-1.3" href="#section-1.3">1.3</a>.  Applicability to Repositories</span>

   Objects can also be distributed via a repository (e.g., Lightweight
   Directory Access Protocol (LDAP) servers, X.500 Directory System
   Agents (DSAs), Web-based servers).  If an object is stored in a
   repository encrypted with a symmetric key algorithm, anyone with the
   shared KEK and access to that object can then decrypt that object.
   The encrypted object and the encrypted, shared KEK can be stored in
   the repository.

<span class="h3"><a class="selflink" id="section-1.4" href="#section-1.4">1.4</a>.  Using the Group Key</span>

   This document was written with three specific scenarios in mind: two
   supporting Mail List Agents and one for general message distribution.
   Scenario 1 depicts the originator sending a public key (PK) protected
   message to an MLA who then uses the shared KEK(s) to redistribute the
   message to the members of the list.  Scenario 2 depicts the
   originator sending a shared KEK protected message to an MLA who then
   redistributes the message to the members of the list (the MLA only
   adds additional recipients).  The key used by the originator could be
   a key shared either amongst all recipients or just between the member
   and the MLA.  Note that if the originator uses a key shared only with
   the MLA, then the MLA will need to decrypt the message and reencrypt
   the message for the list recipients.  Scenario 3 shows an originator
   sending a shared KEK protected message to a group of recipients
   without an intermediate MLA.









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                   +----&gt;                   +----&gt;       +----&gt;
    PK   +-----+ S |         S    +-----+ S |         S  |
   ----&gt; | MLA | --+----&gt;   ----&gt; | MLA | --+----&gt;   ----+----&gt;
         +-----+   |              +-----+   |            |
                   +----&gt;                   +----&gt;       +----&gt;

       Scenario 1               Scenario 2           Scenario 3

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

   Figure 1 depicts the architecture to support symmetric key
   distribution.  The Group List Agent (GLA) supports two distinct
   functions with two different agents:

   -  The Key Management Agent (KMA), which is responsible for
      generating the shared KEKs.

   -  The Group Management Agent (GMA), which is responsible for
      managing the Group List (GL) to which the shared KEKs are
      distributed.

   +----------------------------------------------+
   |              Group List Agent                |    +-------+
   | +------------+    + -----------------------+ |    | Group |
   | |    Key     |    | Group Management Agent | |&lt;--&gt;| List  |
   | | Management |&lt;--&gt;|     +------------+     | |    | Owner |
   | |   Agent    |    |     | Group List |     | |    +-------+
   | +------------+    |     +------------+     | |
   |                   |       /  |  \          | |
   |                   +------------------------+ |
   +----------------------------------------------+
                            /     |      \
                           /      |       \
               +----------+ +---------+ +----------+
               | Member 1 | |   ...   | | Member n |
               +----------+ +---------+ +----------+

        Figure 1 - Key Distribution Architecture

   A GLA may support multiple KMAs.  A GLA in general supports only one
   GMA, but the GMA may support multiple GLs.  Multiple KMAs may support
   a GMA in the same fashion as GLAs support multiple KMAs.  Assigning a
   particular KMA to a GL is beyond the scope of this document.

   Modeling real-world GL implementations shows that there are very
   restrictive GLs, where a human determines GL membership, and very
   open GLs, where there are no restrictions on GL membership.  To
   support this spectrum, the mechanism described herein supports both



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   managed (i.e., where access control is applied) and unmanaged (i.e.,
   where no access control is applied) GLs.  The access control
   mechanism for managed lists is beyond the scope of this document.
   Note: If the distribution for the list is performed by an entity
   other than the originator (e.g., an MLA distributing a mail message),
   this entity can also enforce access control rules.

   In either case, the GL must initially be constructed by an entity
   hereafter called the Group List Owner (GLO).  There may be multiple
   entities who 'own' the GL and who are allowed to make changes to the
   GL's properties or membership.  The GLO determines if the GL will be
   managed or unmanaged and is the only entity that may delete the GL.
   GLO(s) may or may not be GL members.  GLO(s) may also set up lists
   that are closed, where the GLO solely determines GL membership.

   Though Figure 1 depicts the GLA as encompassing both the KMA and GMA
   functions, the two functions could be supported by the same entity or
   they could be supported by two different entities.  If two entities
   are used, they could be located on one or two platforms.  There is
   however a close relationship between the KMA and GMA functions.  If
   the GMA stores all information pertaining to the GLs and the KMA
   merely generates keys, a corrupted GMA could cause havoc.  To protect
   against a corrupted GMA, the KMA would be forced to double check the
   requests it receives to ensure that the GMA did not tamper with them.
   These duplicative checks blur the functionality of the two components
   together.  For this reason, the interactions between the KMA and GMA
   are beyond the scope of this document.

   Proprietary mechanisms may be used to separate the functions by
   strengthening the trust relationship between the two entities.
   Henceforth, the distinction between the two agents is not discussed
   further; the term GLA will be used to address both functions.  It
   should be noted that a corrupt GLA can always cause havoc.

<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>.  Protocol Interactions</span>

   There are existing mechanisms (e.g., listserv and majordomo) to
   manage GLs; however, this document does not address securing these
   mechanisms, as they are not standardized.  Instead, it defines
   protocol interactions, as depicted in Figure 2, used by the GL
   members, GLA, and GLO(s) to manage GLs and distribute shared KEKs.
   The interactions have been divided into administration messages and
   distribution messages.  The administrative messages are the request
   and response messages needed to set up the GL, delete the GL, add
   members to the GL, delete members of the GL, request a group rekey,
   add owners to the GL, remove owners of the GL, indicate a group key
   compromise, refresh a group key, interrogate the GLA, and update
   members' and owners' public key certificates.  The distribution



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   messages are the messages that distribute the shared KEKs.  The
   following sections describe the ASN.1 for both the administration and
   distribution messages.  <a href="#section-4">Section 4</a> describes how to use the
   administration messages, and <a href="#section-5">Section 5</a> describes how to use the
   distribution messages.

      +-----+                   +----------+
      | GLO | &lt;---+      +----&gt; | Member 1 |
      +-----+     |      |      +----------+
                  |      |
   +-----+ &lt;------+      |      +----------+
   | GLA | &lt;-------------+----&gt; |   ...    |
   +-----+               |      +----------+
                         |
                         |      +----------+
                         +----&gt; | Member n |
                                +----------+

        Figure 2 - Protocol Interactions

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

   To avoid creating an entirely new protocol, the Certificate
   Management over CMS (CMC) protocol was chosen as the foundation of
   this protocol.  The main reason for the choice was the layering
   aspect provided by CMC where one or more control attributes are
   included in message, protected with CMS, to request or respond to a
   desired action.  The CMC PKIData structure is used for requests, and
   the CMC PKIResponse structure is used for responses.  The content-
   types PKIData and PKIResponse are then encapsulated in CMS's
   SignedData or EnvelopedData, or a combination of the two (see <a href="#section-3.2">Section</a>
   <a href="#section-3.2">3.2</a>).  The following are the control attributes defined in this
   document:


















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         Control
        Attribute          OID          Syntax
   -------------------  ----------- -----------------
    glUseKEK            id-skd 1    GLUseKEK
    glDelete            id-skd 2    GeneralName
    glAddMember         id-skd 3    GLAddMember
    glDeleteMember      id-skd 4    GLDeleteMember
    glRekey             id-skd 5    GLRekey
    glAddOwner          id-skd 6    GLOwnerAdministration
    glRemoveOwner       id-skd 7    GLOwnerAdministration
    glkCompromise       id-skd 8    GeneralName
    glkRefresh          id-skd 9    GLKRefresh
    glaQueryRequest     id-skd 11   GLAQueryRequest
    glaQueryResponse    id-skd 12   GLAQueryResponse
    glProvideCert       id-skd 13   GLManageCert
    glUpdateCert        id-skd 14   GLManageCert
    glKey               id-skd 15   GLKey

   In the following conformance tables, the column headings have the
   following meanings: O for originate, R for receive, and F for
   forward.  There are three types of implementations: GLOs, GLAs, and
   GL members.  The GLO is an optional component, hence all GLO O and
   GLO R messages are optional, and GLA F messages are optional.  The
   first table includes messages that conformant implementations MUST
   support.  The second table includes messages that MAY be implemented.
   The second table should be interpreted as follows: if the control
   attribute is implemented by a component, then it must be implemented
   as indicated.  For example, if a GLA is implemented that supports the
   glAddMember control attribute, then it MUST support receiving the
   glAddMember message.  Note that "-" means not applicable.

                             Required
          Implementation Requirement       |  Control
     GLO   |        GLA        | GL Member | Attribute
    O  R   |  O      R      F  |  O    R   |
   ------- | ----------------- | --------- | ----------
   MAY  -  | MUST    -     MAY |  -   MUST | glProvideCert
   MAY MAY |  -     MUST   MAY | MUST  -   | glUpdateCert
    -   -  | MUST    -      -  |  -   MUST | glKey












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                             Optional
           Implementation Requirement      |  Control
     GLO   |        GLA        | GL Member | Attribute
    O   R  |  O      R      F  |  O    R   |
   ------- | ----------------- | --------- | ----------
   MAY  -  |  -     MAY     -  |  -    -   | glUseKEK
   MAY  -  |  -     MAY     -  |  -    -   | glDelete
   MAY MAY |  -     MUST   MAY | MUST  -   | glAddMember
   MAY MAY |  -     MUST   MAY | MUST  -   | glDeleteMember
   MAY  -  |  -     MAY     -  |  -    -   | glRekey
   MAY  -  |  -     MAY     -  |  -    -   | glAddOwner
   MAY  -  |  -     MAY     -  |  -    -   | glRemoveOwner
   MAY MAY |  -     MUST   MAY | MUST  -   | glkCompromise
   MAY  -  |  -     MUST    -  | MUST  -   | glkRefresh
   MAY  -  |  -     SHOULD  -  | MAY   -   | glaQueryRequest
    -  MAY | SHOULD  -      -  |  -   MAY  | glaQueryResponse

   glaQueryResponse is carried in the CMC PKIResponse content-type, all
   other control attributes are carried in the CMC PKIData content-type.
   The exception is glUpdateCert, which can be carried in either PKIData
   or PKIResponse.

   Success and failure messages use CMC (see <a href="#section-3.2.4">Section 3.2.4</a>).

<span class="h4"><a class="selflink" id="section-3.1.1" href="#section-3.1.1">3.1.1</a>.  GL Use KEK</span>

   The GLO uses glUseKEK to request that a shared KEK be assigned to a
   GL.  glUseKEK messages MUST be signed by the GLO.  The glUseKEK
   control attribute has the syntax GLUseKEK:

   GLUseKEK ::= SEQUENCE {
     glInfo                GLInfo,
     glOwnerInfo           SEQUENCE SIZE (1..MAX) OF GLOwnerInfo,
     glAdministration      GLAdministration DEFAULT 1,
     glKeyAttributes       GLKeyAttributes OPTIONAL }

   GLInfo ::= SEQUENCE {
     glName     GeneralName,
     glAddress  GeneralName }

   GLOwnerInfo ::= SEQUENCE {
     glOwnerName     GeneralName,
     glOwnerAddress  GeneralName,
     certificate     Certificates OPTIONAL }







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   Certificates ::= SEQUENCE {
      pKC                [0] Certificate OPTIONAL,
                                  -- See [<a href="#ref-PROFILE" title="&quot;Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile&quot;">PROFILE</a>]
      aC                 [1] SEQUENCE SIZE (1.. MAX) OF
                             AttributeCertificate OPTIONAL,
                                  -- See [<a href="#ref-ACPROF" title="&quot;An Internet Attribute Certificate Profile for Authorization&quot;">ACPROF</a>]
      certPath           [2] CertificateSet OPTIONAL }
                                  -- From [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>]

   -- CertificateSet and CertificateChoices are included only
   -- for illustrative purposes as they are imported from [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>].

   CertificateSet ::= SET SIZE (1..MAX) OF CertificateChoices

   -- CertificateChoices supports X.509 public key certificates in
   -- certificates and v2 attribute certificates in v2AttrCert.

   GLAdministration ::= INTEGER {
     unmanaged  (0),
     managed    (1),
     closed     (2) }

   GLKeyAttributes ::= SEQUENCE {
     rekeyControlledByGLO       [0] BOOLEAN DEFAULT FALSE,
     recipientsNotMutuallyAware [1] BOOLEAN DEFAULT TRUE,
     duration                   [2] INTEGER DEFAULT 0,
     generationCounter          [3] INTEGER DEFAULT 2,
     requestedAlgorithm         [4] AlgorithmIdentifier
                                 DEFAULT { id-aes128-wrap } }

   The fields in GLUseKEK have the following meaning:

     - glInfo indicates the name of the GL in glName and the address of
       the GL in glAddress.  The glName and glAddress can be the same,
       but this is not always the case.  Both the name and address MUST
       be unique for a given GLA.

     - glOwnerInfo indicates:

        -- glOwnerName indicates the name of the owner of the GL.  One
           of the names in glOwnerName MUST match one of the names in
           the certificate (either the subject distinguished name or one
           of the subject alternative names) used to sign this
           SignedData.PKIData creating the GL (i.e., the immediate
           signer).

        -- glOwnerAddress indicates the GL owner's address.




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        -- certificates MAY be included.  It contains the following
           three fields:

            --- certificates.pKC includes the encryption certificate for
                the GLO.  It will be used to encrypt responses for the
                GLO.

            --- certificates.aC MAY be included to convey any attribute
                certificate (see [<a href="#ref-ACPROF" title="&quot;An Internet Attribute Certificate Profile for Authorization&quot;">ACPROF</a>]) associated with the
                encryption certificate of the GLO included in
                certificates.pKC.

            --- certificates.certPath MAY also be included to convey
                certificates that might aid the recipient in
                constructing valid certification paths for the
                certificate provided in certificates.pKC and the
                attribute certificates provided in certificates.aC.
                Theses certificates are optional because they might
                already be included elsewhere in the message (e.g., in
                the outer CMS layer).

        -- glAdministration indicates how the GL ought to be
           administered.  The default is for the list to be managed.
           Three values are supported for glAdministration:

            --- Unmanaged - When the GLO sets glAdministration to
                unmanaged, it is allowing prospective members to request
                addition and deletion from the GL without GLO
                intervention.

            --- Managed - When the GLO sets glAdministration to managed,
                it is allowing prospective members to request addition
                and deletion from the GL, but the request is redirected
                by the GLA to GLO for review.  The GLO makes the
                determination as to whether to honor the request.

            --- Closed - When the GLO sets glAdministration to closed,
                it is not allowing prospective members to request
                addition or deletion from the GL.  The GLA will only
                accept glAddMember and glDeleteMember requests from the
                GLO.

        -- glKeyAttributes indicates the attributes the GLO wants the
           GLA to assign to the shared KEK.  If this field is omitted,
           GL rekeys will be controlled by the GLA, the recipients are
           allowed to know about one another, the algorithm will be
           AES-128 (see <a href="#section-7">Section 7</a>), the shared KEK will be valid for a
           calendar month (i.e., first of the month until the last day



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           of the month), and two shared KEKs will be distributed
           initially.  The fields in glKeyAttributes have the following
           meaning:

            --- rekeyControlledByGLO indicates whether the GL rekey
                messages will be generated by the GLO or by the GLA.
                The default is for the GLA to control rekeys.  If GL
                rekey is controlled by the GLA, the GL will continue to
                be rekeyed until the GLO deletes the GL or changes the
                GL rekey to be GLO controlled.

            --- recipientsNotMutuallyAware indicates that the GLO wants
                the GLA to distribute the shared KEK individually for
                each of the GL members (i.e., a separate glKey message
                is sent to each recipient).  The default is for separate
                glKey message not to be required.

                Note: This supports lists where one member does not know
                the identities of the other members.  For example, a
                list is configured granting submit permissions to only
                one member.  All other members are 'listening'.  The
                security policy of the list does not allow the members
                to know who else is on the list.  If a glKey is
                constructed for all of the GL members, information about
                each of the members may be derived from the information
                in RecipientInfos.

                To make sure the glkey message does not divulge
                information about the other recipients, a separate glKey
                message would be sent to each GL member.

            --- duration indicates the length of time (in days) during
                which the shared KEK is considered valid.  The value
                zero (0) indicates that the shared KEK is valid for a
                calendar month in the UTC Zulu time zone.  For example,
                if the duration is zero (0), if the GL shared KEK is
                requested on July 24, the first key will be valid until
                the end of July and the next key will be valid for the
                entire month of August.  If the value is not zero (0),
                the shared KEK will be valid for the number of days
                indicated by the value.  For example, if the value of
                duration is seven (7) and the shared KEK is requested on
                Monday but not generated until Tuesday (13 May 2008);
                the shared KEKs will be valid from Tuesday (13 May 2008)
                to Tuesday (20 May 2008).  The exact time of the day is
                determined when the key is generated.





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            --- generationCounter indicates the number of keys the GLO
                wants the GLA to distribute.  To ensure uninterrupted
                function of the GL, two (2) shared KEKs at a minimum
                MUST be initially distributed.  The second shared KEK is
                distributed with the first shared KEK, so that when the
                first shared KEK is no longer valid the second key can
                be used.  If the GLA controls rekey, then it also
                indicates the number of shared KEKs the GLO wants
                outstanding at any one time.  See Sections <a href="#section-4.5">4.5</a> and <a href="#section-5">5</a> for
                more on rekey.

            --- requestedAlgorithm indicates the algorithm and any
                parameters the GLO wants the GLA to use with the shared
                KEK.  The parameters are conveyed via the
                SMIMECapabilities attribute (see [<a href="#ref-MSG" title="&quot;Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1 Message Specification&quot;">MSG</a>]).  See <a href="#section-6">Section 6</a>
                for more on algorithms.

<span class="h4"><a class="selflink" id="section-3.1.2" href="#section-3.1.2">3.1.2</a>.  Delete GL</span>

   GLOs use glDelete to request that a GL be deleted from the GLA.  The
   glDelete control attribute has the syntax GeneralName.  The glDelete
   message MUST be signed by the GLO.  The name of the GL to be deleted
   is included in GeneralName:

   DeleteGL ::= GeneralName

<span class="h4"><a class="selflink" id="section-3.1.3" href="#section-3.1.3">3.1.3</a>.  Add GL Member</span>

   GLOs use the glAddMember to request addition of new members, and
   prospective GL members use the glAddMember to request their own
   addition to the GL.  The glAddMember message MUST be signed by either
   the GLO or the prospective GL member.  The glAddMember control
   attribute has the syntax GLAddMember:

   GLAddMember ::= SEQUENCE {
     glName    GeneralName,
     glMember  GLMember }

   GLMember ::= SEQUENCE {
     glMemberName     GeneralName,
     glMemberAddress  GeneralName OPTIONAL,
     certificates     Certificates OPTIONAL }

   The fields in GLAddMembers have the following meaning:

     - glName indicates the name of the GL to which the member should be
       added.




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     - glMember indicates the particulars for the GL member.  Both of
       the following fields must be unique for a given GL:

        -- glMemberName indicates the name of the GL member.

        -- glMemberAddress indicates the GL member's address.  It MUST
           be included.

           Note: In some instances, the glMemberName and glMemberAddress
           may be the same, but this is not always the case.

        -- certificates MUST be included.  It contains the following
           three fields:

            --- certificates.pKC includes the member's encryption
                certificate.  It will be used, at least initially, to
                encrypt the shared KEK for that member.  If the message
                is generated by a prospective GL member, the pKC MUST be
                included.  If the message is generated by a GLO, the pKC
                SHOULD be included.

            --- certificates.aC MAY be included to convey any attribute
                certificate (see [<a href="#ref-ACPROF" title="&quot;An Internet Attribute Certificate Profile for Authorization&quot;">ACPROF</a>]) associated with the member's
                encryption certificate.

            --- certificates.certPath MAY also be included to convey
                certificates that might aid the recipient in
                constructing valid certification paths for the
                certificate provided in certificates.pKC and the
                attribute certificates provided in certificates.aC.
                These certificates are optional because they might
                already be included elsewhere in the message (e.g., in
                the outer CMS layer).

<span class="h4"><a class="selflink" id="section-3.1.4" href="#section-3.1.4">3.1.4</a>.  Delete GL Member</span>

   GLOs use the glDeleteMember to request deletion of GL members, and GL
   members use the glDeleteMember to request their own removal from the
   GL.  The glDeleteMember message MUST be signed by either the GLO or
   the GL member.  The glDeleteMember control attribute has the syntax
   GLDeleteMember:

   GLDeleteMember ::= SEQUENCE {
     glName            GeneralName,
     glMemberToDelete  GeneralName }






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   The fields in GLDeleteMembers have the following meaning:

     - glName indicates the name of the GL from which the member should
       be removed.

     - glMemberToDelete indicates the name or address of the member to
       be deleted.

<span class="h4"><a class="selflink" id="section-3.1.5" href="#section-3.1.5">3.1.5</a>.  Rekey GL</span>

   GLOs use the glRekey to request a GL rekey.  The glRekey message MUST
   be signed by the GLO.  The glRekey control attribute has the syntax
   GLRekey:

   GLRekey ::= SEQUENCE {
     glName              GeneralName,
     glAdministration    GLAdministration OPTIONAL,
     glNewKeyAttributes  GLNewKeyAttributes OPTIONAL,
     glRekeyAllGLKeys    BOOLEAN OPTIONAL }

   GLNewKeyAttributes ::= SEQUENCE {
     rekeyControlledByGLO       [0] BOOLEAN OPTIONAL,
     recipientsNotMutuallyAware [1] BOOLEAN OPTIONAL,
     duration                   [2] INTEGER OPTIONAL,
     generationCounter          [3] INTEGER OPTIONAL,
     requestedAlgorithm         [4] AlgorithmIdentifier OPTIONAL }

   The fields in GLRekey have the following meaning:

     - glName indicates the name of the GL to be rekeyed.

     - glAdministration indicates if there is any change to how the GL
       should be administered.  See <a href="#section-3.1.1">Section 3.1.1</a> for the three options.
       This field is only included if there is a change from the
       previously registered glAdministration.

     - glNewKeyAttributes indicates whether the rekey of the GLO is
       controlled by the GLA or GL, what algorithm and parameters the
       GLO wishes to use, the duration of the key, and how many keys
       will be issued.  The field is only included if there is a change
       from the previously registered glKeyAttributes.

     - glRekeyAllGLKeys indicates whether the GLO wants all of the
       outstanding GL's shared KEKs rekeyed.  If it is set to TRUE then
       all outstanding KEKs MUST be issued.  If it is set to FALSE then
       all outstanding KEKs need not be reissued.





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<span class="h4"><a class="selflink" id="section-3.1.6" href="#section-3.1.6">3.1.6</a>.  Add GL Owner</span>

   GLOs use the glAddOwner to request that a new GLO be allowed to
   administer the GL.  The glAddOwner message MUST be signed by a
   registered GLO.  The glAddOwner control attribute has the syntax
   GLOwnerAdministration:

   GLOwnerAdministration ::= SEQUENCE {
     glName       GeneralName,
     glOwnerInfo  GLOwnerInfo }

   The fields in GLAddOwners have the following meaning:

     - glName indicates the name of the GL to which the new GLO should
       be associated.

     - glOwnerInfo indicates the name, address, and certificates of the
       new GLO.  As this message includes names of new GLOs, the
       certificates.pKC MUST be included, and it MUST include the
       encryption certificate of the new GLO.

<span class="h4"><a class="selflink" id="section-3.1.7" href="#section-3.1.7">3.1.7</a>.  Remove GL Owner</span>

   GLOs use the glRemoveOwner to request that a GLO be disassociated
   with the GL.  The glRemoveOwner message MUST be signed by a
   registered GLO.  The glRemoveOwner control attribute has the syntax
   GLOwnerAdministration:

   GLOwnerAdministration ::= SEQUENCE {
     glName       GeneralName,
     glOwnerInfo  GLOwnerInfo }

   The fields in GLRemoveOwners have the following meaning:

     - glName indicates the name of the GL to which the GLO should be
       disassociated.

     - glOwnerInfo indicates the name and address of the GLO to be
       removed.  The certificates field SHOULD be omitted, as it will be
       ignored.

<span class="h4"><a class="selflink" id="section-3.1.8" href="#section-3.1.8">3.1.8</a>.  GL Key Compromise</span>

   GL members and GLOs use glkCompromise to indicate that the shared KEK
   possessed has been compromised.  The glKeyCompromise control
   attribute has the syntax GeneralName.  This message is always
   redirected by the GLA to the GLO for further action.  The
   glkCompromise MAY be included in an EnvelopedData generated with the



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   compromised shared KEK.  The name of the GL to which the compromised
   key is associated is placed in GeneralName:

   GLKCompromise ::= GeneralName

<span class="h4"><a class="selflink" id="section-3.1.9" href="#section-3.1.9">3.1.9</a>.  GL Key Refresh</span>

   GL members use the glkRefresh to request that the shared KEK be
   redistributed to them.  The glkRefresh control attribute has the
   syntax GLKRefresh.

   GLKRefresh ::= SEQUENCE {
     glName  GeneralName,
     dates   SEQUENCE SIZE (1..MAX) OF Date }

   Date ::= SEQUENCE {
     start GeneralizedTime,
     end   GeneralizedTime OPTIONAL }

   The fields in GLKRefresh have the following meaning:

     - glName indicates the name of the GL for which the GL member wants
       shared KEKs.

     - dates indicates a date range for keys the GL member wants.  The
       start field indicates the first date the GL member wants and the
       end field indicates the last date.  The end date MAY be omitted
       to indicate the GL member wants all keys from the specified start
       date to the current date.  Note that a procedural mechanism is
       needed to restrict users from accessing messages that they are
       not allowed to access.

<span class="h4"><a class="selflink" id="section-3.1.10" href="#section-3.1.10">3.1.10</a>.  GLA Query Request and Response</span>

   There are situations where GLOs and GL members may need to determine
   some information from the GLA about the GL.  GLOs and GL members use
   the glaQueryRequest, defined in <a href="#section-3.1.10.1">Section 3.1.10.1</a>, to request
   information and GLAs use the glaQueryResponse, defined in <a href="#section-3.1.10.2">Section</a>
   <a href="#section-3.1.10.2">3.1.10.2</a>, to return the requested information.  <a href="#section-3.1.10.3">Section 3.1.10.3</a>
   includes one request and response type and value; others may be
   defined in additional documents.

<span class="h5"><a class="selflink" id="section-3.1.10.1" href="#section-3.1.10.1">3.1.10.1</a>.  GLA Query Request</span>

   GLOs and GL members use the glaQueryRequest to ascertain information
   about the GLA.  The glaQueryRequest control attribute has the syntax
   GLAQueryRequest:




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   GLAQueryRequest ::= SEQUENCE {
     glaRequestType   OBJECT IDENTIFIER,
     glaRequestValue  ANY DEFINED BY glaRequestType }

<span class="h5"><a class="selflink" id="section-3.1.10.2" href="#section-3.1.10.2">3.1.10.2</a>.  GLA Query Response</span>

   GLAs return the glaQueryResponse after receiving a GLAQueryRequest.
   The glaQueryResponse MUST be signed by a GLA.  The glaQueryResponse
   control attribute has the syntax GLAQueryResponse:

   GLAQueryResponse ::= SEQUENCE {
     glaResponseType   OBJECT IDENTIFIER,
     glaResponseValue  ANY DEFINED BY glaResponseType }

<span class="h5"><a class="selflink" id="section-3.1.10.3" href="#section-3.1.10.3">3.1.10.3</a>.  Request and Response Types</span>

   Requests and responses are registered as a pair under the following
   object identifier arc:

   id-cmc-glaRR OBJECT IDENTIFIER ::= { id-cmc 99 }

   This document defines one request/response pair for GL members and
   GLOs to query the GLA for the list of algorithm it supports.  The
   following Object Identifier (OID) is included in the glaQueryType
   field:

   id-cmc-gla-skdAlgRequest OBJECT IDENTIFIER ::={ id-cmc-glaRR 1 }

   SKDAlgRequest ::= NULL

   If the GLA supports GLAQueryRequest and GLAQueryResponse messages,
   the GLA may return the following OID in the glaQueryType field:

   id-cmc-gla-skdAlgResponse OBJECT IDENTIFIER ::= { id-cmc-glaRR 2 }

   The glaQueryValue has the form of the smimeCapabilities attributes as
   defined in [<a href="#ref-MSG" title="&quot;Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1 Message Specification&quot;">MSG</a>].

<span class="h4"><a class="selflink" id="section-3.1.11" href="#section-3.1.11">3.1.11</a>.  Provide Cert</span>

   GLAs and GLOs use the glProvideCert to request that a GL member
   provide an updated or new encryption certificate.  The glProvideCert
   message MUST be signed by either GLA or GLO.  If the GL member's PKC
   has been revoked, the GLO or GLA MUST NOT use it to generate the
   EnvelopedData that encapsulates the glProvideCert request.  The
   glProvideCert control attribute has the syntax GLManageCert:





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   GLManageCert ::= SEQUENCE {
     glName    GeneralName,
     glMember  GLMember }

   The fields in GLManageCert have the following meaning:

     - glName indicates the name of the GL to which the GL member's new
       certificate is to be associated.

     - glMember indicates particulars for the GL member:

        -- glMemberName indicates the GL member's name.

        -- glMemberAddress indicates the GL member's address.  It MAY be
           omitted.

        -- certificates SHOULD be omitted.

<span class="h4"><a class="selflink" id="section-3.1.12" href="#section-3.1.12">3.1.12</a> Update Cert</span>

   GL members and GLOs use the glUpdateCert to provide a new certificate
   for the GL.  GL members can generate an unsolicited glUpdateCert or
   generate a response glUpdateCert as a result of receiving a
   glProvideCert message.  GL members MUST sign the glUpdateCert.  If
   the GL member's encryption certificate has been revoked, the GL
   member MUST NOT use it to generate the EnvelopedData that
   encapsulates the glUpdateCert request or response.  The glUpdateCert
   control attribute has the syntax GLManageCert:

   GLManageCert ::= SEQUENCE {
     glName    GeneralName,
     glMember  GLMember }

   The fields in GLManageCert have the following meaning:

     - glName indicates the name of the GL to which the GL member's new
       certificate should be associated.

     - glMember indicates the particulars for the GL member:

        -- glMemberName indicates the GL member's name.

        -- glMemberAddress indicates the GL member's address.  It MAY be
           omitted.

        -- certificates MAY be omitted if the GLManageCert message is
           sent to request the GL member's certificate; otherwise, it
           MUST be included.  It includes the following three fields:



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            --- certificates.pKC includes the member's encryption
                certificate that will be used to encrypt the shared KEK
                for that member.

            --- certificates.aC MAY be included to convey one or more
                attribute certificates associated with the member's
                encryption certificate.

            --- certificates.certPath MAY also be included to convey
                certificates that might aid the recipient in
                constructing valid certification paths for the
                certificate provided in certificates.pKC and the
                attribute certificates provided in certificates.aC.
                These certificates are optional because they might
                already be included elsewhere in the message (e.g., in
                the outer CMS layer).

<span class="h4"><a class="selflink" id="section-3.1.13" href="#section-3.1.13">3.1.13</a>.  GL Key</span>

   The GLA uses the glKey to distribute the shared KEK.  The glKey
   message MUST be signed by the GLA.  The glKey control attribute has
   the syntax GLKey:

   GLKey ::= SEQUENCE {
     glName        GeneralName,
     glIdentifier  KEKIdentifier,      -- See [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>]
     glkWrapped    RecipientInfos,     -- See [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>]
     glkAlgorithm  AlgorithmIdentifier,
     glkNotBefore  GeneralizedTime,
     glkNotAfter   GeneralizedTime }

   -- KEKIdentifier is included only for illustrative purposes as
   -- it is imported from [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>].

   KEKIdentifier ::= SEQUENCE {
     keyIdentifier OCTET STRING,
     date GeneralizedTime OPTIONAL,
     other OtherKeyAttribute OPTIONAL }

   The fields in GLKey have the following meaning:

     - glName is the name of the GL.

     - glIdentifier is the key identifier of the shared KEK.  See
       Section 6.2.3 of [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>] for a description of the subfields.






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     - glkWrapped is the wrapped shared KEK for the GL for a particular
       duration.  The RecipientInfos MUST be generated as specified in
       Section 6.2 of [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>].  The ktri RecipientInfo choice MUST be
       supported.  The key in the EncryptedKey field (i.e., the
       distributed shared KEK) MUST be generated according to the
       section concerning random number generation in the security
       considerations of [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>].

     - glkAlgorithm identifies the algorithm with which the shared KEK
       is used.  Since no encrypted data content is being conveyed at
       this point, the parameters encoded with the algorithm should be
       the structure defined for smimeCapabilities rather than encrypted
       content.

     - glkNotBefore indicates the date at which the shared KEK is
       considered valid.  GeneralizedTime values MUST be expressed in
       UTC (Zulu) and MUST include seconds (i.e., times are
       YYYYMMDDHHMMSSZ), even where the number of seconds is zero.
       GeneralizedTime values MUST NOT include fractional seconds.

     - glkNotAfter indicates the date after which the shared KEK is
       considered invalid.  GeneralizedTime values MUST be expressed in
       UTC (Zulu) and MUST include seconds (i.e., times are
       YYYYMMDDHHMMSSZ), even where the number of seconds is zero.
       GeneralizedTime values MUST NOT include fractional seconds.

   If the glKey message is in response to a glUseKEK message:

     - The GLA MUST generate separate glKey messages for each recipient
       if glUseKEK.glKeyAttributes.recipientsNotMutuallyAware is set to
       TRUE.  For each recipient, you want to generate a message that
       contains that recipient's key (i.e., one message with one
       attribute).

     - The GLA MUST generate the requested number of glKey messages.
       The value in glUseKEK.glKeyAttributes.generationCounter indicates
       the number of glKey messages requested.

   If the glKey message is in response to a glRekey message:

     - The GLA MUST generate separate glKey messages for each recipient
       if glRekey.glNewKeyAttributes.recipientsNotMutuallyAware is set
       to TRUE.

     - The GLA MUST generate the requested number of glKey messages.
       The value in glUseKEK.glKeyAttributes.generationCounter indicates
       the number of glKey messages requested.




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     - The GLA MUST generate one glKey message for each outstanding
       shared KEKs for the GL when glRekeyAllGLKeys is set to TRUE.

   If the glKey message was not in response to a glRekey or glUseKEK
   (e.g., where the GLA controls rekey):

     - The GLA MUST generate separate glKey messages for each recipient
       when glUseKEK.glNewKeyAttributes.recipientsNotMutuallyAware that
       set up the GL was set to TRUE.

     - The GLA MAY generate glKey messages prior to the duration on the
       last outstanding shared KEK expiring, where the number of glKey
       messages generated is generationCounter minus one (1).  Other
       distribution mechanisms can also be supported to support this
       functionality.

<span class="h3"><a class="selflink" id="section-3.2" href="#section-3.2">3.2</a>.  Use of CMC, CMS, and PKIX</span>

   The following sections outline the use of CMC, CMS, and the PKIX
   certificate and CRL profile.

<span class="h4"><a class="selflink" id="section-3.2.1" href="#section-3.2.1">3.2.1</a>.  Protection Layers</span>

   The following sections outline the protection required for the
   control attributes defined in this document.

   Note: There are multiple ways to encapsulate SignedData and
   EnvelopedData.  The first is to use a MIME wrapper around each
   ContentInfo, as specified in [<a href="#ref-MSG" title="&quot;Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1 Message Specification&quot;">MSG</a>].  The second is not to use a MIME
   wrapper around each ContentInfo, as specified in Transporting S/MIME
   Objects in X.400 [<a href="#ref-X400TRANS" title="&quot;Transporting Secure/Multipurpose Internet Mail Extensions (S/MIME) Objects in X.400&quot;">X400TRANS</a>].

<span class="h5"><a class="selflink" id="section-3.2.1.1" href="#section-3.2.1.1">3.2.1.1</a>.  Minimum Protection</span>

   At a minimum, a SignedData MUST protect each request and response
   encapsulated in PKIData and PKIResponse.  The following is a
   depiction of the minimum wrappings:

   Minimum Protection
   ------------------
   SignedData
    PKIData or PKIResponse
     controlSequence

   Prior to taking any action on any request or response SignedData(s)
   MUST be processed according to [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>].





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<span class="h5"><a class="selflink" id="section-3.2.1.2" href="#section-3.2.1.2">3.2.1.2</a>.  Additional Protection</span>

   An additional EnvelopedData MAY also be used to provide
   confidentiality of the request and response.  An additional
   SignedData MAY also be added to provide authentication and integrity
   of the encapsulated EnvelopedData.  The following is a depiction of
   the optional additional wrappings:

                                  Authentication and Integrity
   Confidentiality Protection     of Confidentiality Protection
   --------------------------     -----------------------------
   EnvelopedData                  SignedData
    SignedData                     EnvelopedData
     PKIData or PKIResponse         SignedData
      controlSequence                PKIData or PKIResponse
                                      controlSequence

   If an incoming message is encrypted, the confidentiality of the
   message MUST be preserved.  All EnvelopedData objects MUST be
   processed as specified in [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>].  If a SignedData is added over an
   EnvelopedData, a ContentHints attribute SHOULD be added.  See <a href="#section-2.9">Section</a>
   <a href="#section-2.9">2.9</a> of Extended Security Services for S/MIME [<a href="#ref-ESS" title="&quot;Enhanced Security Services for S/MIME&quot;">ESS</a>].

   If the GLO or GL member applies confidentiality to a request, the
   EnvelopedData MUST include the GLA as a recipient.  If the GLA
   forwards the GL member request to the GLO, then the GLA MUST decrypt
   the EnvelopedData content, strip the confidentiality layer, and apply
   its own confidentiality layer as an EnvelopedData with the GLO as a
   recipient.

<span class="h4"><a class="selflink" id="section-3.2.2" href="#section-3.2.2">3.2.2</a>.  Combining Requests and Responses</span>

   Multiple requests and responses corresponding to a GL MAY be included
   in one PKIData.controlSequence or PKIResponse.controlSequence.
   Requests and responses for multiple GLs MAY be combined in one
   PKIData or PKIResponse by using PKIData.cmsSequence and
   PKIResponse.cmsSequence.  A separate cmsSequence MUST be used for
   different GLs.  That is, requests corresponding to two different GLs
   are included in different cmsSequences.  The following is a diagram
   depicting multiple requests and responses combined in one PKIData and
   PKIResponse:










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       Multiple Requests and Responses
   Request                        Response
   -------                        --------
   SignedData                      SignedData
    PKIData                         PKIResponse
     cmsSequence                     cmsSequence
      SignedData                      SignedData
       PKIData                         PKIResponse
        controlSequence                 controlSequence
         One or more requests            One or more responses
         corresponding to one GL         corresponding to one GL
      SignedData                      SignedData
       PKIData                         PKIResponse
        controlSequence                 controlSequence
         One or more requests            One or more responses
         corresponding to another GL     corresponding to another GL

   When applying confidentiality to multiple requests and responses, all
   of the requests/responses MAY be included in one EnvelopedData.  The
   following is a depiction:

   Confidentiality of Multiple Requests and Responses
   Wrapped Together
   ----------------
   EnvelopedData
    SignedData
     PKIData
      cmsSequence
       SignedData
        PKIResponse
         controlSequence
          One or more requests
          corresponding to one GL
       SignedData
        PKIData
         controlSequence
          One or more requests
          corresponding to one GL













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   Certain combinations of requests in one PKIData.controlSequence and
   one PKIResponse.controlSequence are not allowed.  The invalid
   combinations listed here MUST NOT be generated:

      Invalid Combinations
   ---------------------------
   glUseKEK   &amp; glDeleteMember
   glUseKEK   &amp; glRekey
   glUseKEK   &amp; glDelete
   glDelete   &amp; glAddMember
   glDelete   &amp; glDeleteMember
   glDelete   &amp; glRekey
   glDelete   &amp; glAddOwner
   glDelete   &amp; glRemoveOwner

   To avoid unnecessary errors, certain requests and responses SHOULD be
   processed prior to others.  The following is the priority of message
   processing, if not listed it is an implementation decision as to
   which to process first: glUseKEK before glAddMember, glRekey before
   glAddMember, and glDeleteMember before glRekey.  Note that there is a
   processing priority, but it does not imply an ordering within the
   content.

<span class="h4"><a class="selflink" id="section-3.2.3" href="#section-3.2.3">3.2.3</a>.  GLA Generated Messages</span>

   When the GLA generates a success or fail message, it generates one
   for each request.  SKDFailInfo values of unsupportedDuration,
   unsupportedDeliveryMethod, unsupportedAlgorithm, noGLONameMatch,
   nameAlreadyInUse, alreadyAnOwner, and notAnOwner are not returned to
   GL members.

   If GLKeyAttributes.recipientsNotMutuallyAware is set to TRUE, a
   separate PKIResponse.cMCStatusInfoExt and PKIData.glKey MUST be
   generated for each recipient.  However, it is valid to send one
   message with multiple attributes to the same recipient.

   If the GL has multiple GLOs, the GLA MUST send cMCStatusInfoExt
   messages to the requesting GLO.  The mechanism to determine which GLO
   made the request is beyond the scope of this document.

   If a GL is managed and the GLA receives a glAddMember,
   glDeleteMember, or glkCompromise message, the GLA redirects the
   request to the GLO for review.  An additional, SignedData MUST be
   applied to the redirected request as follows:







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   GLA Forwarded Requests
   ----------------------
   SignedData
    PKIData
      cmsSequence
        SignedData
         PKIData
          controlSequence

<span class="h4"><a class="selflink" id="section-3.2.4" href="#section-3.2.4">3.2.4</a>.  CMC Control Attributes and CMS Signed Attributes</span>

   CMC carries control attributes as CMS signed attributes.  These
   attributes are defined in [<a href="#ref-CMC" title="&quot;Certificate Management over CMS (CMC)&quot;">CMC</a>] and [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>].  Some of these attributes
   are REQUIRED; others are OPTIONAL.  The required attributes are as
   follows: cMCStatusInfoExt transactionId, senderNonce, recipientNonce,
   queryPending, and signingTime.  Other attributes can also be used;
   however, their use is beyond the scope of this document.  The
   following sections specify requirements in addition to those already
   specified in [<a href="#ref-CMC" title="&quot;Certificate Management over CMS (CMC)&quot;">CMC</a>] and [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>].

<span class="h5"><a class="selflink" id="section-3.2.4.1" href="#section-3.2.4.1">3.2.4.1</a>.  Using cMCStatusInfoExt</span>

   cMCStatusInfoExt is used by GLAs to indicate to GLOs and GL members
   that a request was unsuccessful.  Two classes of failure codes are
   used within this document.  Errors from the CMCFailInfo list, found
   in <a href="#section-5.1.4">Section 5.1.4</a> of CMC, are encoded as defined in CMC.  Error codes
   defined in this document are encoded using the ExtendedFailInfo field
   of the cmcStatusInfoExt structure.  If the same failure code applies
   to multiple commands, a single cmcStatusInfoExt structure can be used
   with multiple items in cMCStatusInfoExt.bodyList.  The GLA MAY also
   return other pertinent information in statusString.  The SKDFailInfo
   object identifier and value are:

   id-cet-skdFailInfo OBJECT IDENTIFIER ::= { iso(1)
     identified-organization(3) dod(6) internet(1) security(5)
     mechanisms(5) pkix(7) cet(15) skdFailInfo(1) }

   SKDFailInfo ::= INTEGER {
     unspecified           (0),
     closedGL              (1),
     unsupportedDuration   (2),
     noGLACertificate      (3),
     invalidCert           (4),
     unsupportedAlgorithm  (5),
     noGLONameMatch        (6),
     invalidGLName         (7),
     nameAlreadyInUse      (8),
     noSpam                (9),



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   -- obsolete             (10),
     alreadyAMember        (11),
     notAMember            (12),
     alreadyAnOwner        (13),
     notAnOwner            (14) }

   The values have the following meaning:

     - unspecified indicates that the GLA is unable or unwilling to
       perform the requested action and does not want to indicate the
       reason.

     - closedGL indicates that members can only be added or deleted by
       the GLO.

     - unsupportedDuration indicates that the GLA does not support
       generating keys that are valid for the requested duration.

     - noGLACertificate indicates that the GLA does not have a valid
       certificate.

     - invalidCert indicates that the member's encryption certificate
       was not verifiable (i.e., signature did not validate,
       certificate's serial number present on a CRL, the certificate
       expired, etc.).

     - unsupportedAlgorithm indicates the GLA does not support the
       requested algorithm.

     - noGLONameMatch indicates that one of the names in the certificate
       used to sign a request does not match the name of a registered
       GLO.

     - invalidGLName indicates that the GLA does not support the glName
       present in the request.

     - nameAlreadyInUse indicates that the glName is already assigned on
       the GLA.

     - noSpam indicates that the prospective GL member did not sign the
       request (i.e., if the name in glMember.glMemberName does not
       match one of the names (either the subject distinguished name or
       one of the subject alternative names) in the certificate used to
       sign the request).

     - alreadyAMember indicates that the prospective GL member is
       already a GL member.




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     - notAMember indicates that the prospective GL member to be deleted
       is not presently a GL member.

     - alreadyAnOwner indicates that the prospective GLO is already a
       GLO.

     - notAnOwner indicates that the prospective GLO to be deleted is
       not presently a GLO.

   cMCStatusInfoExt is used by GLAs to indicate to GLOs and GL members
   that a request was successfully completed.  If the request was
   successful, the GLA returns a cMCStatusInfoExt response with
   cMCStatus.success and optionally other pertinent information in
   statusString.

   When the GL is managed and the GLO has reviewed GL member initiated
   glAddMember, glDeleteMember, and glkComrpomise requests, the GLO uses
   cMCStatusInfoExt to indicate the success or failure of the request.
   If the request is allowed, cMCStatus.success is returned and
   statusString is optionally returned to convey additional information.
   If the request is denied, cMCStatus.failed is returned and
   statusString is optionally returned to convey additional information.
   Additionally, the appropriate SKDFailInfo can be included in
   cMCStatusInfoExt.extendedFailInfo.

   cMCStatusInfoExt is used by GLOs, GLAs, and GL members to indicate
   that signature verification failed.  If the signature failed to
   verify over any control attribute except a cMCStatusInfoExt, a
   cMCStatusInfoExt control attribute MUST be returned indicating
   cMCStatus.failed and otherInfo.failInfo.badMessageCheck.  If the
   signature over the outermost PKIData failed, the bodyList value is
   zero (0).  If the signature over any other PKIData failed, the
   bodyList value is the bodyPartId value from the request or response.
   GLOs and GL members who receive cMCStatusInfoExt messages whose
   signatures are invalid SHOULD generate a new request to avoid
   badMessageCheck message loops.

   cMCStatusInfoExt is also used by GLOs and GLAs to indicate that a
   request could not be performed immediately.  If the request could not
   be processed immediately by the GLA or GLO, the cMCStatusInfoExt
   control attribute MUST be returned indicating cMCStatus.pending and
   otherInfo.pendInfo.  When requests are redirected to the GLO for
   approval (for managed lists), the GLA MUST NOT return a
   cMCStatusInfoExt indicating query pending.







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   cMCStatusInfoExt is also used by GLAs to indicate that a
   glaQueryRequest is not supported.  If the glaQueryRequest is not
   supported, the cMCStatusInfoExt control attribute MUST be returned
   indicating cMCStatus.noSupport and statusString is optionally
   returned to convey additional information.

   cMCStatusInfoExt is also used by GL members, GLOs, and GLAs to
   indicate that the signingTime (see <a href="#section-3.2.4.3">Section 3.2.4.3</a>) is not close
   enough to the locally specified time.  If the local time is not close
   enough to the time specified in signingTime, a cMCStatus.failed and
   otherInfo.failInfo.badTime MAY be returned.

<span class="h5"><a class="selflink" id="section-3.2.4.2" href="#section-3.2.4.2">3.2.4.2</a>.  Using transactionId</span>

   transactionId MAY be included by GLOs, GLAs, or GL members to
   identify a given transaction.  All subsequent requests and responses
   related to the original request MUST include the same transactionId
   control attribute.  If GL members include a transactionId and the
   request is redirected to the GLO, the GLA MAY include an additional
   transactionId in the outer PKIData.  If the GLA included an
   additional transactionId in the outer PKIData, when the GLO generates
   a cMCStatusInfoExt response it generates one for the GLA with the
   GLA's transactionId and one for the GL member with the GL member's
   transactionId.

<span class="h5"><a class="selflink" id="section-3.2.4.3" href="#section-3.2.4.3">3.2.4.3</a>.  Using Nonces and signingTime</span>

   The use of nonces (see Section 5.6 of [<a href="#ref-CMC" title="&quot;Certificate Management over CMS (CMC)&quot;">CMC</a>]) and an indication of
   when the message was signed (see Section 11.3 of [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>]) can be used
   to provide application-level replay prevention.

   To protect the GL, all messages MUST include the signingTime
   attribute.  Message originators and recipients can then use the time
   provided in this attribute to determine whether they have previously
   received the message.

   If the originating message includes a senderNonce, the response to
   the message MUST include the received senderNonce value as the
   recipientNonce and a new value as the senderNonce value in the
   response.

   If a GLA aggregates multiple messages together or forwards a message
   to a GLO, the GLA MAY optionally generate a new nonce value and
   include that in the wrapping message.  When the response comes back
   from the GLO, the GLA builds a response to the originator(s) of the
   message(s) and deals with each of the nonce values from the
   originating messages.




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   For these attributes, it is necessary to maintain state information
   on exchanges to compare one result to another.  The time period for
   which this information is maintained is a local policy.

<span class="h5"><a class="selflink" id="section-3.2.4.4" href="#section-3.2.4.4">3.2.4.4</a>.  CMC and CMS Attribute Support Requirements</span>

   The following are the implementation requirements for CMC control
   attributes and CMS signed attributes for an implementation to be
   considered conformant to this specification:

          Implementation Requirement     |
      GLO    |      GLA      | GL Member | Attribute
    O    R   |  O    R    F  |  O    R   |
   --------- | ------------- | --------- | ----------
   MUST MUST | MUST MUST  -  | MUST MUST | cMCStatusInfoExt
   MAY  MAY  | MUST MUST  -  | MAY  MAY  | transactionId
   MAY  MAY  | MUST MUST  -  | MAY  MAY  | senderNonce
   MAY  MAY  | MUST MUST  -  | MAY  MAY  | recepientNonce
   MUST MUST | MUST MUST  -  | MUST MUST | SKDFailInfo
   MUST MUST | MUST MUST  -  | MUST MUST | signingTime

<span class="h4"><a class="selflink" id="section-3.2.5" href="#section-3.2.5">3.2.5</a>.  Resubmitted GL Member Messages</span>

   When the GL is managed, the GLA forwards the GL member requests to
   the GLO for GLO approval by creating a new request message containing
   the GL member request(s) as a cmsSequence item.  If the GLO approves
   the request, it can either add a new layer of wrapping and send it
   back to the GLA or create a new message and send it to the GLA.
   (Note in this case there are now 3 layers of PKIData messages with
   appropriate signing layers.)

<span class="h4"><a class="selflink" id="section-3.2.6" href="#section-3.2.6">3.2.6</a>.  PKIX Certificate and CRL Profile</span>

   Signatures, certificates, and CRLs are verified according to the PKIX
   profile [<a href="#ref-PROFILE" title="&quot;Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile&quot;">PROFILE</a>].

   Name matching is performed according to the PKIX profile [<a href="#ref-PROFILE" title="&quot;Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile&quot;">PROFILE</a>].

   All distinguished name forms must follow the UTF8String convention
   noted in the PKIX profile [<a href="#ref-PROFILE" title="&quot;Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile&quot;">PROFILE</a>].

   A certificate per GL would be issued to the GLA.

   GL policy may mandate that the GL member's address be included in the
   GL member's certificate.






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

   There are a number of administrative messages that must be exchanged
   to manage a GL.  The following sections describe each request and
   response message combination in detail.  The procedures defined in
   this section are not prescriptive.

<span class="h3"><a class="selflink" id="section-4.1" href="#section-4.1">4.1</a>.  Assign KEK to GL</span>

   Prior to generating a group key, a GL needs to be set up and a shared
   KEK assigned to the GL.  Figure 3 depicts the protocol interactions
   to set up and assign a shared KEK.  Note that error messages are not
   depicted in Figure 3.  Additionally, behavior for the optional
   transactionId, senderNonce, and recipientNonce CMC control attributes
   is not addressed in these procedures.

    +-----+  1     2  +-----+
    | GLA | &lt;-------&gt; | GLO |
    +-----+           +-----+

   Figure 3 - Create Group List

   The process is as follows:

   1 - The GLO is the entity responsible for requesting the creation of
       the GL.  The GLO sends a
       SignedData.PKIData.controlSequence.glUseKEK request to the GLA (1
       in Figure 3).  The GLO MUST include glName, glAddress,
       glOwnerName, glOwnerAddress, and glAdministration.  The GLO MAY
       also include their preferences for the shared KEK in
       glKeyAttributes by indicating whether the GLO controls the rekey
       in rekeyControlledByGLO, whether separate glKey messages should
       be sent to each recipient in recipientsNotMutuallyAware, the
       requested algorithm to be used with the shared KEK in
       requestedAlgorithm, the duration of the shared KEK, and how many
       shared KEKs should be initially distributed in generationCounter.
       The GLO MUST also include the signingTime attribute with this
       request.

     1.a - If the GLO knows of members to be added to the GL, the
           glAddMember request(s) MAY be included in the same
           controlSequence as the glUseKEK request (see <a href="#section-3.2.2">Section 3.2.2</a>).
           The GLO indicates the same glName in the glAddMember request
           as in glUseKEK.glInfo.glName.  Further glAddMember procedures
           are covered in <a href="#section-4.3">Section 4.3</a>.






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<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


     1.b - The GLO can apply confidentiality to the request by
           encapsulating the SignedData.PKIData in an EnvelopedData (see
           <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

     1.c - The GLO can also optionally apply another SignedData over the
           EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   2 - Upon receipt of the request, the GLA checks the signingTime and
       verifies the signature on the innermost SignedData.PKIData.  If
       an additional SignedData and/or EnvelopedData encapsulates the
       request (see Sections <a href="#section-3.2.1.2">3.2.1.2</a> and <a href="#section-3.2.2">3.2.2</a>), the GLA verifies the
       outer signature(s) and/or decrypts the outer layer(s) prior to
       verifying the signature on the innermost SignedData.

     2.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLA MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.

     2.b - Else if signature processing continues and if the signatures
           do not verify, the GLA returns a cMCStatusInfoExt response
           indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.  Additionally, a
           signingTime attribute is included with the response.

     2.c - Else if the signatures do verify but the GLA does not have a
           valid certificate, the GLA returns a cMCStatusInfoExt with
           cMCStatus.failed and otherInfo.extendedFailInfo.SKDFailInfo
           value of noValidGLACertificate.  Additionally, a signingTime
           attribute is included with the response.  Instead of
           immediately returning the error code, the GLA attempts to get
           a certificate, possibly using [<a href="#ref-CMC" title="&quot;Certificate Management over CMS (CMC)&quot;">CMC</a>].

     2.d - Else the signatures are valid and the GLA does have a valid
           certificate, the GLA checks that one of the names in the
           certificate used to sign the request matches one of the names
           in glUseKEK.glOwnerInfo.glOwnerName.

       2.d.1 - If the names do not match, the GLA returns a response
               indicating cMCStatusInfoExt with cMCStatus.failed and
               otherInfo.extendedFailInfo.SKDFailInfo value of
               noGLONameMatch.  Additionally, a signingTime attribute is
               included with the response.








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<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


       2.d.2 - Else if the names all match, the GLA checks that the
               glName and glAddress are not already in use.  The GLA
               also checks any glAddMember included within the
               controlSequence with this glUseKEK.  Further processing
               of the glAddMember is covered in <a href="#section-4.3">Section 4.3</a>.

         2.d.2.a - If the glName is already in use, the GLA returns a
                   response indicating cMCStatusInfoExt with
                   cMCStatus.failed and
                   otherInfo.extendedFailInfo.SKDFailInfo value of
                   nameAlreadyInUse.  Additionally, a signingTime
                   attribute is included with the response.

         2.d.2.b - Else if the requestedAlgorithm is not supported, the
                   GLA returns a response indicating cMCStatusInfoExt
                   with cMCStatus.failed and
                   otherInfo.extendedFailInfo.SKDFailInfo value of
                   unsupportedAlgorithm.  Additionally, a signingTime
                   attribute is included with the response.

         2.d.2.c - Else if the duration cannot be supported, determining
                   this is beyond the scope of this document, the GLA
                   returns a response indicating cMCStatusInfoExt with
                   cMCStatus.failed and
                   otherInfo.extendedFailInfo.SKDFailInfo value of
                   unsupportedDuration.  Additionally, a signingTime
                   attribute is included with the response.

         2.d.2.d - Else if the GL cannot be supported for other reasons,
                   which the GLA does not wish to disclose, the GLA
                   returns a response indicating cMCStatusInfoExt with
                   cMCStatus.failed and
                   otherInfo.extendedFailInfo.SKDFailInfo value of
                   unspecified.  Additionally, a signingTime attribute
                   is included with the response.

         2.d.2.e - Else if the glName is not already in use, the
                   duration can be supported, and the requestedAlgorithm
                   is supported, the GLA MUST return a cMCStatusInfoExt
                   indicating cMCStatus.success and a signingTime
                   attribute. (2 in Figure 3).  The GLA also takes
                   administrative actions, which are beyond the scope of
                   this document, to store the glName, glAddress,
                   glKeyAttributes, glOwnerName, and glOwnerAddress.
                   The GLA also sends a glKey message as described in
                   <a href="#section-5">section 5</a>.





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<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


           2.d.2.e.1 - The GLA can apply confidentiality to the response
                       by encapsulating the SignedData.PKIResponse in an
                       EnvelopedData if the request was encapsulated in
                       an EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

           2.d.2.e.2 - The GLA can also optionally apply another
                       SignedData over the EnvelopedData (see <a href="#section-3.2.1.2">Section</a>
                       <a href="#section-3.2.1.2">3.2.1.2</a>).

   3 - Upon receipt of the cMCStatusInfoExt responses, the GLO checks
       the signingTime and verifies the GLA signature(s).  If an
       additional SignedData and/or EnvelopedData encapsulates the
       response (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GLO verifies the
       outer signature and/or decrypts the outer layer prior to
       verifying the signature on the innermost SignedData.

     3.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLO MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.

     3.b - Else if signature processing continues and if the signatures
           do verify, the GLO MUST check that one of the names in the
           certificate used to sign the response matches the name of the
           GL.

       3.b.1 - If the name of the GL does not match the name present in
               the certificate used to sign the message, the GLO should
               not believe the response.

       3.b.2 - Else if the name of the GL does match the name present in
               the certificate and:

         3.b.2.a - If the signatures do verify and the response was
                   cMCStatusInfoExt indicating cMCStatus.success, the
                   GLO has successfully created the GL.

         3.b.2.b - Else if the signatures are valid and the response is
                   cMCStatusInfoExt.cMCStatus.failed with any reason,
                   the GLO can reattempt to create the GL using the
                   information provided in the response.  The GLO can
                   also use the glaQueryRequest to determine the
                   algorithms and other characteristics supported by the
                   GLA (see <a href="#section-4.9">Section 4.9</a>).







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<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


<span class="h3"><a class="selflink" id="section-4.2" href="#section-4.2">4.2</a>.  Delete GL from GLA</span>

   From time to time, there are instances when a GL is no longer needed.
   In this case, the GLO deletes the GL.  Figure 4 depicts the protocol
   interactions to delete a GL.  Note that behavior for the optional
   transactionId, senderNonce, and recipientNonce CMC control attributes
   is not addressed in these procedures.

       +-----+   1    2  +-----+
       | GLA | &lt;-------&gt; | GLO |
       +-----+           +-----+

      Figure 4 - Delete Group List

   The process is as follows:

   1 - The GLO is responsible for requesting the deletion of the GL.
       The GLO sends a SignedData.PKIData.controlSequence.glDelete
       request to the GLA (1 in Figure 4).  The name of the GL to be
       deleted is included in GeneralName.  The GLO MUST also include
       the signingTime attribute and can also include a transactionId
       and senderNonce attributes.

     1.a - The GLO can optionally apply confidentiality to the request
           by encapsulating the SignedData.PKIData in an EnvelopedData
           (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

     1.b - The GLO MAY optionally apply another SignedData over the
           EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   2 - Upon receipt of the request, the GLA checks the signingTime and
       verifies the signature on the innermost SignedData.PKIData.  If
       an additional SignedData and/or EnvelopedData encapsulates the
       request (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GLA verifies the
       outer signature and/or decrypts the outer layer prior to
       verifying the signature on the innermost SignedData.

     2.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLA MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.

     2.b - Else if signature processing continues and if the signatures
           cannot be verified, the GLA returns a cMCStatusInfoExt
           response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.  Additionally, a
           signingTime attribute is included with the response.




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<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


     2.c - Else if the signatures verify, the GLA makes sure the GL is
           supported by checking the name of the GL matches a glName
           stored on the GLA.

       2.c.1 - If the glName is not supported by the GLA, the GLA
               returns a response indicating cMCStatusInfoExt with
               cMCStatus.failed and
               otherInfo.extendedFailInfo.SKDFailInfo value of
               invalidGLName.  Additionally, a signingTime attribute is
               included with the response.

       2.c.2 - Else if the glName is supported by the GLA, the GLA
               ensures that a registered GLO signed the glDelete request
               by checking if one of the names present in the digital
               signature certificate used to sign the glDelete request
               matches a registered GLO.

         2.c.2.a - If the names do not match, the GLA returns a response
                   indicating cMCStatusInfoExt with cMCStatus.failed and
                   otherInfo.extendedFailInfo.SKDFailInfo value of
                   noGLONameMatch.  Additionally, a signingTime
                   attribute is included with the response.

         2.c.2.b - Else if the names do match, but the GL cannot be
                   deleted for other reasons, which the GLA does not
                   wish to disclose, the GLA returns a response
                   indicating cMCStatusInfoExt with cMCStatus.failed and
                   otherInfo.extendedFailInfo.SKDFailInfo value of
                   unspecified.  Additionally, a signingTime attribute
                   is included with the response.  Actions beyond the
                   scope of this document must then be taken to delete
                   the GL from the GLA.

         2.c.2.c - Else if the names do match, the GLA returns a
                   cMCStatusInfoExt indicating cMCStatus.success and a
                   signingTime attribute (2 in Figure 4).  The GLA ought
                   not accept further requests for member additions,
                   member deletions, or group rekeys for this GL.

           2.c.2.c.1 - The GLA can apply confidentiality to the response
                       by encapsulating the SignedData.PKIResponse in an
                       EnvelopedData if the request was encapsulated in
                       an EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

           2.c.2.c.2 - The GLA MAY optionally apply another SignedData
                       over the EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).





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<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


   3 - Upon receipt of the cMCStatusInfoExt response, the GLO checks the
       signingTime and verifies the GLA signature(s).  If an additional
       SignedData and/or EnvelopedData encapsulates the response (see
       <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GLO verifies the outer signature
       and/or decrypts the outer layer prior to verifying the signature
       on the innermost SignedData.

     3.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLO MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.

     3.b - Else if signature processing continues and if the signatures
           verify, the GLO checks that one of the names in the
           certificate used to sign the response matches the name of the
           GL.

       3.b.1 - If the name of the GL does not match the name present in
               the certificate used to sign the message, the GLO should
               not believe the response.

       3.b.2 - Else if the name of the GL does match the name present in
               the certificate and:

         3.b.2.a - If the signatures verify and the response was
                   cMCStatusInfoExt indicating cMCStatus.success, the
                   GLO has successfully deleted the GL.

         3.b.2.b - Else if the signatures do verify and the response was
                   cMCStatusInfoExt.cMCStatus.failed with any reason,
                   the GLO can reattempt to delete the GL using the
                   information provided in the response.

<span class="h3"><a class="selflink" id="section-4.3" href="#section-4.3">4.3</a>.  Add Members to GL</span>

   To add members to GLs, either the GLO or prospective members use the
   glAddMember request.  The GLA processes GLO and prospective GL member
   requests differently though.  GLOs can submit the request at any time
   to add members to the GL, and the GLA, once it has verified the
   request came from a registered GLO, should process it.  If a
   prospective member sends the request, the GLA needs to determine how
   the GL is administered.  When the GLO initially configured the GL, it
   set the GL to be unmanaged, managed, or closed (see <a href="#section-3.1.1">Section 3.1.1</a>).
   In the unmanaged case, the GLA merely processes the member's request.
   In the managed case, the GLA forwards the requests from the
   prospective members to the GLO for review.  Where there are multiple
   GLOs for a GL, which GLO the request is forwarded to is beyond the
   scope of this document.  The GLO reviews the request and either



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<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


   rejects it or submits a reformed request to the GLA.  In the closed
   case, the GLA will not accept requests from prospective members.  The
   following sections describe the processing for the GLO(s), GLA, and
   prospective GL members depending on where the glAddMeber request
   originated, either from a GLO or from prospective members.  Figure 5
   depicts the protocol interactions for the three options.  Note that
   the error messages are not depicted.  Additionally, note that
   behavior for the optional transactionId, senderNonce, and
   recipientNonce CMC control attributes is not addressed in these
   procedures.

      +-----+  2,B{A}              3  +----------+
      | GLO | &lt;--------+    +-------&gt; | Member 1 |
      +-----+          |    |         +----------+
               1       |    |
      +-----+ &lt;--------+    |      3  +----------+
      | GLA |  A            +-------&gt; |   ...    |
      +-----+ &lt;-------------+         +----------+
                            |
                            |      3  +----------+
                            +-------&gt; | Member n |
                                      +----------+

         Figure 5 - Member Addition

   An important decision that needs to be made on a group-by-group basis
   is whether to rekey the group every time a new member is added.
   Typically, unmanaged GLs should not be rekeyed when a new member is
   added, as the overhead associated with rekeying the group becomes
   prohibitive, as the group becomes large.  However, managed and closed
   GLs can be rekeyed to maintain the confidentiality of the traffic
   sent by group members.  An option to rekeying managed or closed GLs
   when a member is added is to generate a new GL with a different group
   key.  Group rekeying is discussed in Sections <a href="#section-4.5">4.5</a> and <a href="#section-5">5</a>.

<span class="h4"><a class="selflink" id="section-4.3.1" href="#section-4.3.1">4.3.1</a>.  GLO Initiated Additions</span>

   The process for GLO initiated glAddMember requests is as follows:

   1 - The GLO collects the pertinent information for the member(s) to
       be added (this may be done through an out-of-bands means).  The
       GLO then sends a SignedData.PKIData.controlSequence with a
       separate glAddMember request for each member to the GLA (1 in
       Figure 5).  The GLO includes the GL name in glName, the member's
       name in glMember.glMemberName, the member's address in
       glMember.glMemberAddress, and the member's encryption certificate
       in glMember.certificates.pKC.  The GLO can also include any
       attribute certificates associated with the member's encryption



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<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


       certificate in glMember.certificates.aC, and the certification
       path associated with the member's encryption and attribute
       certificates in glMember.certificates.certPath.  The GLO MUST
       also include the signingTime attribute with this request.

     1.a - The GLO can optionally apply confidentiality to the request
           by encapsulating the SignedData.PKIData in an EnvelopedData
           (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

     1.b - The GLO can also optionally apply another SignedData over the
           EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   2 - Upon receipt of the request, the GLA checks the signingTime and
       verifies the signature on the innermost SignedData.PKIData.  If
       an additional SignedData and/or EnvelopedData encapsulates the
       request (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GLA verifies the
       outer signature and/or decrypts the outer layer prior to
       verifying the signature on the innermost SignedData.

     2.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLA MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.

     2.b - Else if signature processing continues and if the signatures
           cannot be verified, the GLA returns a cMCStatusInfoExt
           response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.  Additionally, a
           signingTime attribute is included with the response.

     2.c - Else if the signatures verify, the glAddMember request is
           included in a controlSequence with the glUseKEK request, and
           the processing in <a href="#section-4.1">Section 4.1</a> item 2.d is successfully
           completed, the GLA returns a cMCStatusInfoExt indicating
           cMCStatus.success and a signingTime attribute (2 in Figure
           5).

       2.c.1 - The GLA can apply confidentiality to the response by
               encapsulating the SignedData.PKIData in an EnvelopedData
               if the request was encapsulated in an EnvelopedData (see
               <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

       2.c.2 - The GLA can also optionally apply another SignedData over
               the EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).







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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-41" ></span>
<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


     2.d - Else if the signatures verify and the GLAddMember request is
           not included in a controlSequence with the GLCreate request,
           the GLA makes sure the GL is supported by checking that the
           glName matches a glName stored on the GLA.

       2.d.1 - If the glName is not supported by the GLA, the GLA
               returns a response indicating cMCStatusInfoExt with
               cMCStatus.failed and
               otherInfo.extendedFailInfo.SKDFailInfo value of
               invalidGLName.  Additionally, a signingTime attribute is
               included with the response.

       2.d.2 - Else if the glName is supported by the GLA, the GLA
               checks to see if the glMemberName is present on the GL.

         2.d.2.a - If the glMemberName is present on the GL, the GLA
                   returns a response indicating cMCStatusInfoExt with
                   cMCStatus.failed and
                   otherInfo.extendedFailInfo.SKDFailInfo value of
                   alreadyAMember.  Additionally, a signingTime
                   attribute is included with the response.

         2.d.2.b - Else if the glMemberName is not present on the GL,
                   the GLA checks how the GL is administered.

           2.d.2.b.1 - If the GL is closed, the GLA checks that a
                       registered GLO signed the request by checking
                       that one of the names in the digital signature
                       certificate used to sign the request matches a
                       registered GLO.

             2.d.2.b.1.a - If the names do not match, the GLA returns a
                           response indicating cMCStatusInfoExt with
                           cMCStatus.failed and
                           otherInfo.extendedFailInfo.SKDFailInfo value
                           of noGLONameMatch.  Additionally, a
                           signingTime attribute is included with the
                           response.

             2.d.2.b.1.b - Else if the names match, the GLA verifies the
                           member's encryption certificate.

               2.d.2.b.1.b.1 - If the member's encryption certificate
                               cannot be verified, the GLA can return a
                               response indicating cMCStatusInfoExt with
                               cMCStatus.failed and
                               otherInfo.extendedFailInfo.SKDFailInfo
                               value of invalidCert to the GLO.



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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-42" ></span>
<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


                               Additionally, a signingTime attribute is
                               included with the response.  If the GLA
                               does not return a
                               cMCStatusInfoExt.cMCStatus.failed
                               response, the GLA issues a glProvideCert
                               request (see <a href="#section-4.10">Section 4.10</a>).

               2.d.2.b.1.b.2 - Else if the member's certificate
                               verifies, the GLA returns a
                               cMCStatusInfoExt indicating
                               cMCStatus.success and a signingTime
                               attribute (2 in Figure 5).  The GLA also
                               takes administrative actions, which are
                               beyond the scope of this document, to add
                               the member to the GL stored on the GLA.
                               The GLA also distributes the shared KEK
                               to the member via the mechanism described
                               in <a href="#section-5">Section 5</a>.

                 2.d.2.b.1.b.2.a - The GLA applies confidentiality to
                                   the response by encapsulating the
                                   SignedData.PKIData in an
                                   EnvelopedData if the request was
                                   encapsulated in an EnvelopedData (see
                                   <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

                 2.d.2.b.1.b.2.b - The GLA can also optionally apply
                                   another SignedData over the
                                   EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

           2.d.2.b.2 - Else if the GL is managed, the GLA checks that
                       either a registered GLO or the prospective member
                       signed the request.  For GLOs, one of the names
                       in the certificate used to sign the request needs
                       to match a registered GLO.  For the prospective
                       member, the name in glMember.glMemberName needs
                       to match one of the names in the certificate used
                       to sign the request.

             2.d.2.b.2.a - If the signer is neither a registered GLO nor
                           the prospective GL member, the GLA returns a
                           response indicating cMCStatusInfoExt with
                           cMCStatus.failed and
                           otherInfo.extendedFailInfo.SKDFailInfo value
                           of noSpam.  Additionally, a signingTime
                           attribute is included with the response.





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<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


             2.d.2.b.2.b - Else if the signer is a registered GLO, the
                           GLA verifies the member's encryption
                           certificate.

               2.d.2.b.2.b.1 - If the member's certificate cannot be
                               verified, the GLA can return a response
                               indicating cMCStatusInfoExt with
                               cMCStatus.failed and
                               otherInfo.extendedFailInfo.SKDFailInfo
                               value of invalidCert.  Additionally, a
                               signingTime attribute is included with
                               the response.  If the GLA does not return
                               a cMCStatus.failed response, the GLA MUST
                               issue a glProvideCert request (see
                               <a href="#section-4.10">Section 4.10</a>).

               2.d.2.b.2.b.2 - Else if the member's certificate
                               verifies, the GLA MUST return a
                               cMCStatusInfoExt indicating
                               cMCStatus.success and a signingTime
                               attribute to the GLO (2 in Figure 5).
                               The GLA also takes administrative
                               actions, which are beyond the scope of
                               this document, to add the member to the
                               GL stored on the GLA.  The GLA also
                               distributes the shared KEK to the member
                               via the mechanism described in <a href="#section-5">Section 5</a>.
                               The GL policy may mandate that the GL
                               member's address be included in the GL
                               member's certificate.

                 2.d.2.b.2.b.2.a - The GLA applies confidentiality to
                                   the response by encapsulating the
                                   SignedData.PKIData in an
                                   EnvelopedData if the request was
                                   encapsulated in an EnvelopedData (see
                                   <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

                 2.d.2.b.2.b.2.b - The GLA can also optionally apply
                                   another SignedData over the
                                   EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

             2.d.2.b.2.c - Else if the signer is the prospective member,
                           the GLA forwards the glAddMember request (see
                           <a href="#section-3.2.3">Section 3.2.3</a>) to a registered GLO (B{A} in
                           Figure 5).  If there is more than one
                           registered GLO, the GLO to which the request
                           is forwarded is beyond the scope of this



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                           document.  Further processing of the
                           forwarded request by GLOs is addressed in 3
                           of <a href="#section-4.3.2">Section 4.3.2</a>.

               2.d.2.b.2.c.1 - The GLA applies confidentiality to the
                               forwarded request by encapsulating the
                               SignedData.PKIData in an EnvelopedData if
                               the original request was encapsulated in
                               an EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

               2.d.2.b.2.c.2 - The GLA can also optionally apply another
                               SignedData over the EnvelopedData (see
                               <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

           2.d.2.b.3 - Else if the GL is unmanaged, the GLA checks that
                       either a registered GLO or the prospective member
                       signed the request.  For GLOs, one of the names
                       in the certificate used to sign the request needs
                       to match the name of a registered GLO.  For the
                       prospective member, the name in
                       glMember.glMemberName needs to match one of the
                       names in the certificate used to sign the
                       request.

             2.d.2.b.3.a - If the signer is neither a registered GLO nor
                           the prospective member, the GLA returns a
                           response indicating cMCStatusInfoExt with
                           cMCStatus.failed and
                           otherInfo.extendedFailInfo.SKDFailInfo value
                           of noSpam.  Additionally, a signingTime
                           attribute is included with the response.

             2.d.2.b.3.b - Else if the signer is either a registered GLO
                           or the prospective member, the GLA verifies
                           the member's encryption certificate.

               2.d.2.b.3.b.1 - If the member's certificate cannot be
                               verified, the GLA can return a response
                               indicating cMCStatusInfoExt with
                               cMCStatus.failed and
                               otherInfo.extendedFailInfo.SKDFailInfo
                               value of invalidCert and a signingTime
                               attribute to either the GLO or the
                               prospective member depending on where the
                               request originated.  If the GLA does not
                               return a cMCStatus.failed response, the
                               GLA issues a glProvideCert request (see




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                               <a href="#section-4.10">Section 4.10</a>) to either the GLO or
                               prospective member depending on where the
                               request originated.

               2.d.2.b.3.b.2 - Else if the member's certificate
                               verifies, the GLA returns a
                               cMCStatusInfoExt indicating
                               cMCStatus.success and a signingTime
                               attribute to the GLO (2 in Figure 5) if
                               the GLO signed the request and to the GL
                               member (3 in Figure 5) if the GL member
                               signed the request.  The GLA also takes
                               administrative actions, which are beyond
                               the scope of this document, to add the
                               member to the GL stored on the GLA.  The
                               GLA also distributes the shared KEK to
                               the member via the mechanism described in
                               <a href="#section-5">Section 5</a>.

                 2.d.2.b.3.b.2.a - The GLA applies confidentiality to
                                   the response by encapsulating the
                                   SignedData.PKIData in an
                                   EnvelopedData if the request was
                                   encapsulated in an EnvelopedData (see
                                   <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

                 2.d.2.b.3.b.2.b - The GLA can also optionally apply
                                   another SignedData over the
                                   EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   3 - Upon receipt of the cMCStatusInfoExt response, the GLO checks the
       signingTime and verifies the GLA signature(s).  If an additional
       SignedData and/or EnvelopedData encapsulates the response (see
       <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GLO verifies the outer signature
       and/or decrypts the outer layer prior to verifying the signature
       on the innermost SignedData.

     3.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLO MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.

     3.b - Else if signature processing continues and if the signatures
           verify, the GLO checks that one of the names in the
           certificate used to sign the response matches the name of the
           GL.





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       3.b.1 - If the name of the GL does not match the name present in
               the certificate used to sign the message, the GLO should
               not believe the response.

       3.b.2 - Else if the name of the GL matches the name present in
               the certificate and:

         3.b.2.a - If the signatures verify and the response is
                   cMCStatusInfoExt indicating cMCStatus.success, the
                   GLA has added the member to the GL.  If the member
                   was added to a managed list and the original request
                   was signed by the member, the GLO sends a
                   cMCStatusInfoExt.cMCStatus.success and a signingTime
                   attribute to the GL member.

         3.b.2.b - Else if the GLO received a
                   cMCStatusInfoExt.cMCStatus.failed with any reason,
                   the GLO can reattempt to add the member to the GL
                   using the information provided in the response.

   4 - Upon receipt of the cMCStatusInfoExt response, the prospective
       member checks the signingTime and verifies the GLA signatures or
       GLO signatures.  If an additional SignedData and/or EnvelopedData
       encapsulates the response (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GLO
       verifies the outer signature and/or decrypts the outer layer
       prior to verifying the signature on the innermost SignedData.

     4.a - If the signingTime attribute value is not within the locally
           accepted time window, the prospective member MAY return a
           response indicating cMCStatus.failed and
           otherInfo.failInfo.badTime and a signingTime attribute.

     4.b - Else if signature processing continues and if the signatures
           verify, the GL member checks that one of the names in the
           certificate used to sign the response matches the name of the
           GL.

       4.b.1 - If the name of the GL does not match the name present in
               the certificate used to sign the message, the GL member
               should not believe the response.

     4.b.2 - Else if the name of the GL matches the name present in the
               certificate and:

         4.b.2.a - If the signatures verify, the prospective member has
                   been added to the GL.





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         4.b.2.b - Else if the prospective member received a
                   cMCStatusInfoExt.cMCStatus.failed, for any reason,
                   the prospective member MAY reattempt to add itself to
                   the GL using the information provided in the
                   response.

<span class="h4"><a class="selflink" id="section-4.3.2" href="#section-4.3.2">4.3.2</a>.  Prospective Member Initiated Additions</span>

   The process for prospective member initiated glAddMember requests is
   as follows:

   1 - The prospective GL member sends a
       SignedData.PKIData.controlSequence.glAddMember request to the GLA
       (A in Figure 5).  The prospective GL member includes: the GL name
       in glName, their name in glMember.glMemberName, their address in
       glMember.glMemberAddress, and their encryption certificate in
       glMember.certificates.pKC.  The prospective GL member can also
       include any attribute certificates associated with their
       encryption certificate in glMember.certificates.aC, and the
       certification path associated with their encryption and attribute
       certificates in glMember.certificates.certPath.  The prospective
       member MUST also include the signingTime attribute with this
       request.

     1.a - The prospective GL member can optionally apply
           confidentiality to the request by encapsulating the
           SignedData.PKIData in an EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

     1.b - The prospective GL member MAY optionally apply another
           SignedData over the EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   2 - Upon receipt of the request, the GLA verifies the request as per
       2 in <a href="#section-4.3.1">Section 4.3.1</a>.

   3 - Upon receipt of the forwarded request, the GLO checks the
       signingTime and verifies the prospective GL member signature on
       the innermost SignedData.PKIData and the GLA signature on the
       outer layer.  If an EnvelopedData encapsulates the innermost
       layer (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GLO decrypts the outer
       layer prior to verifying the signature on the innermost
       SignedData.

       Note: For cases where the GL is closed and either a) a
       prospective member sends directly to the GLO or b) the GLA has
       mistakenly forwarded the request to the GLO, the GLO should first
       determine whether to honor the request.





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     3.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLO MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime.

     3.b - Else if signature processing continues and if the signatures
           verify, the GLO checks to make sure one of the names in the
           certificate used to sign the request matches the name in
           glMember.glMemberName.

       3.b.1 - If the names do not match, the GLO sends a
               SignedData.PKIResponse.controlSequence message back to
               the prospective member with
               cMCStatusInfoExt.cMCStatus.failed indicating why the
               prospective member was denied in
               cMCStausInfo.statusString.  This stops people from adding
               people to GLs without their permission.  Additionally, a
               signingTime attribute is included with the response.

       3.b.2 - Else if the names match, the GLO determines whether the
               prospective member is allowed to be added.  The mechanism
               is beyond the scope of this document; however, the GLO
               should check to see that the glMember.glMemberName is not
               already on the GL.

         3.b.2.a - If the GLO determines the prospective member is not
                   allowed to join the GL, the GLO can return a
                   SignedData.PKIResponse.controlSequence message back
                   to the prospective member with
                   cMCStatusInfoExt.cMCtatus.failed indicating why the
                   prospective member was denied in
                   cMCStatus.statusString.  Additionally, a signingTime
                   attribute is included with the response.

         3.b.2.b - Else if the GLO determines the prospective member is
                   allowed to join the GL, the GLO verifies the member's
                   encryption certificate.

           3.b.2.b.1 - If the member's certificate cannot be verified,
                       the GLO returns a
                       SignedData.PKIResponse.controlSequence back to
                       the prospective member with
                       cMCStatusInfoExt.cMCtatus.failed indicating that
                       the member's encryption certificate did not
                       verify in cMCStatus.statusString.  Additionally,
                       a signingTime attribute is included with the
                       response.  If the GLO does not return a
                       cMCStatusInfoExt response, the GLO sends a




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                       SignedData.PKIData.controlSequence.glProvideCert
                       message to the prospective member requesting a
                       new encryption certificate (see <a href="#section-4.10">Section 4.10</a>).

           3.b.2.b.2 - Else if the member's certificate verifies, the
                       GLO resubmits the glAddMember request (see
                       <a href="#section-3.2.5">Section 3.2.5</a>) to the GLA (1 in Figure 5).

             3.b.2.b.2.a - The GLO applies confidentiality to the new
                           GLAddMember request by encapsulating the
                           SignedData.PKIData in an EnvelopedData if the
                           initial request was encapsulated in an
                           EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

             3.b.2.b.2.b - The GLO can also optionally apply another
                           SignedData over the EnvelopedData (see
                           <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   4 - Processing continues as in 2 of <a href="#section-4.3.1">Section 4.3.1</a>.

<span class="h3"><a class="selflink" id="section-4.4" href="#section-4.4">4.4</a>.  Delete Members from GL</span>

   To delete members from GLs, either the GLO or members to be removed
   use the glDeleteMember request.  The GLA processes the GLO, and
   members requesting their own removal make requests differently.  The
   GLO can submit the request at any time to delete members from the GL,
   and the GLA, once it has verified the request came from a registered
   GLO, should delete the member.  If a member sends the request, the
   GLA needs to determine how the GL is administered.  When the GLO
   initially configured the GL, it set the GL to be unmanaged, managed,
   or closed (see <a href="#section-3.1.1">Section 3.1.1</a>).  In the unmanaged case, the GLA merely
   processes the member's request.  In the managed case, the GLA
   forwards the requests from the member to the GLO for review.  Where
   there are multiple GLOs for a GL, which GLO the request is forwarded
   to is beyond the scope of this document.  The GLO reviews the request
   and either rejects it or submits a reformed request to the GLA.  In
   the closed case, the GLA will not accept requests from members.  The
   following sections describe the processing for the GLO(s), GLA, and
   GL members depending on where the request originated, either from a
   GLO or from members wanting to be removed.  Figure 6 depicts the
   protocol interactions for the three options.  Note that the error
   messages are not depicted.  Additionally, behavior for the optional
   transactionId, senderNonce, and recipientNonce CMC control attributes
   is not addressed in these procedures.







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   +-----+  2,B{A}              3  +----------+
   | GLO | &lt;--------+    +-------&gt; | Member 1 |
   +-----+          |    |         +----------+
            1       |    |
   +-----+ &lt;--------+    |      3  +----------+
   | GLA |  A            +-------&gt; |   ...    |
   +-----+ &lt;-------------+         +----------+
                         |
                         |      3  +----------+
                         +-------&gt; | Member n |
                                   +----------+

       Figure 6 - Member Deletion

   If the member is not removed from the GL, it will continue to receive
   and be able to decrypt data protected with the shared KEK and will
   continue to receive rekeys.  For unmanaged lists, there is no point
   to a group rekey because there is no guarantee that the member
   requesting to be removed has not already added itself back on the GL
   under a different name.  For managed and closed GLs, the GLO needs to
   take steps to ensure that the member being deleted is not on the GL
   twice.  After ensuring this, managed and closed GLs can be rekeyed to
   maintain the confidentiality of the traffic sent by group members.
   If the GLO is sure the member has been deleted, the group rekey
   mechanism can be used to distribute the new key (see Sections <a href="#section-4.5">4.5</a> and
   5).

<span class="h4"><a class="selflink" id="section-4.4.1" href="#section-4.4.1">4.4.1</a>.  GLO Initiated Deletions</span>

   The process for GLO initiated glDeleteMember requests is as follows:

   1 - The GLO collects the pertinent information for the member(s) to
       be deleted (this can be done through an out-of-band means).  The
       GLO then sends a SignedData.PKIData.controlSequence with a
       separate glDeleteMember request for each member to the GLA (1 in
       Figure 6).  The GLO MUST include the GL name in glName and the
       member's name in glMemberToDelete.  If the GL from which the
       member is being deleted is a closed or managed GL, the GLO MUST
       also generate a glRekey request and include it with the
       glDeletemember request (see <a href="#section-4.5">Section 4.5</a>).  The GLO MUST also
       include the signingTime attribute with this request.

     1.a - The GLO can optionally apply confidentiality to the request
           by encapsulating the SignedData.PKIData in an EnvelopedData
           (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

     1.b - The GLO can also optionally apply another SignedData over the
           EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).



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   2 - Upon receipt of the request, the GLA checks the signingTime
       attribute and verifies the signature on the innermost
       SignedData.PKIData.  If an additional SignedData and/or
       EnvelopedData encapsulates the request (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or
       3.2.2), the GLA verifies the outer signature and/or decrypts the
       outer layer prior to verifying the signature on the innermost
       SignedData.

     2.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLA MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.

     2.b - Else if signature processing continues and if the signatures
           cannot be verified, the GLA returns a cMCStatusInfoExt
           response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.  Additionally, a
           signingTime attribute is included with the response.

     2.c - Else if the signatures verify, the GLA makes sure the GL is
           supported by the GLA by checking that the glName matches a
           glName stored on the GLA.

       2.c.1 - If the glName is not supported by the GLA, the GLA
               returns a response indicating cMCStatusInfoExt with
               cMCStatus.failed and
               otherInfo.extendedFailInfo.SKDFailInfo value of
               invalidGLName.  Additionally, a signingTime attribute is
               included with the response.

       2.c.2 - Else if the glName is supported by the GLA, the GLA
               checks to see if the glMemberName is present on the GL.

         2.c.2.a - If the glMemberName is not present on the GL, the GLA
                   returns a response indicating cMCStatusInfoExt with
                   cMCStatus.failed and
                   otherInfo.extendedFailInfo.SKDFailInfo value of
                   notAMember.  Additionally, a signingTime attribute is
                   included with the response.

         2.c.2.b - Else if the glMemberName is already on the GL, the
                   GLA checks how the GL is administered.

           2.c.2.b.1 - If the GL is closed, the GLA checks that the
                       registered GLO signed the request by checking
                       that one of the names in the digital signature
                       certificate used to sign the request matches the
                       registered GLO.



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             2.c.2.b.1.a - If the names do not match, the GLA returns a
                           response indicating cMCStatusInfoExt with
                           cMCStatus.failed and
                           otherInfo.extendedFailInfo.SKDFailInfo value
                           of closedGL.  Additionally, a signingTime
                           attribute is included with the response.

             2.c.2.b.1.b - Else if the names do match, the GLA returns a
                           cMCStatusInfoExt.cMCStatus.success and a
                           signingTime attribute (2 in Figure 5).  The
                           GLA also takes administrative actions, which
                           are beyond the scope of this document, to
                           delete the member with the GL stored on the
                           GLA.  Note that the GL also needs to be
                           rekeyed as described in <a href="#section-5">Section 5</a>.

               2.c.2.b.1.b.1 - The GLA applies confidentiality to the
                               response by encapsulating the
                               SignedData.PKIData in an EnvelopedData if
                               the request was encapsulated in an
                               EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

               2.c.2.b.1.b.2 - The GLA can also optionally apply another
                               SignedData over the EnvelopedData (see
                               <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

           2.c.2.b.2 - Else if the GL is managed, the GLA checks that
                       either a registered GLO or the prospective member
                       signed the request.  For GLOs, one of the names
                       in the certificate used to sign the request needs
                       to match a registered GLO.  For the prospective
                       member, the name in glMember.glMemberName needs
                       to match one of the names in the certificate used
                       to sign the request.

             2.c.2.b.2.a - If the signer is neither a registered GLO nor
                           the prospective GL member, the GLA returns a
                           response indicating cMCStatusInfoExt with
                           cMCStatus.failed and
                           otherInfo.extendedFailInfo.SKDFailInfo value
                           of noSpam.  Additionally, a signingTime
                           attribute is included with the response.

             2.c.2.b.2.b - Else if the signer is a registered GLO, the
                           GLA returns a
                           cMCStatusInfoExt.cMCStatus.success and a
                           signingTime attribute(2 in Figure 6).  The
                           GLA also takes administrative actions, which



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                           are beyond the scope of this document, to
                           delete the member with the GL stored on the
                           GLA.  Note that the GL will also be rekeyed
                           as described in <a href="#section-5">Section 5</a>.

               2.c.2.b.2.b.1 - The GLA applies confidentiality to the
                               response by encapsulating the
                               SignedData.PKIData in an EnvelopedData if
                               the request was encapsulated in an
                               EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

               2.c.2.b.2.b.2 - The GLA can also optionally apply another
                               SignedData over the EnvelopedData (see
                               <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

             2.c.2.b.2.c - Else if the signer is the prospective member,
                           the GLA forwards the glDeleteMember request
                           (see <a href="#section-3.2.3">Section 3.2.3</a>) to the GLO (B{A} in
                           Figure 6).  If there is more than one
                           registered GLO, the GLO to which the request
                           is forwarded to is beyond the scope of this
                           document.  Further processing of the
                           forwarded request by GLOs is addressed in 3
                           of <a href="#section-4.4.2">Section 4.4.2</a>.

               2.c.2.b.2.c.1 - The GLA applies confidentiality to the
                               forwarded request by encapsulating the
                               SignedData.PKIData in an EnvelopedData if
                               the request was encapsulated in an
                               EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

               2.c.2.b.2.c.2 - The GLA can also optionally apply another
                               SignedData over the EnvelopedData (see
                               <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

           2.c.2.b.3 - Else if the GL is unmanaged, the GLA checks that
                       either a registered GLO or the prospective member
                       signed the request.  For GLOs, one of the names
                       in the certificate used to sign the request needs
                       to match the name of a registered GLO.  For the
                       prospective member, the name in
                       glMember.glMemberName needs to match one of the
                       names in the certificate used to sign the
                       request.







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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-54" ></span>
<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


             2.c.2.b.3.a - If the signer is neither the GLO nor the
                           prospective member, the GLA returns a
                           response indicating cMCStatusInfoExt with
                           cMCStatus.failed and
                           otherInfo.extendedFailInfo.SKDFailInfo value
                           of noSpam.  Additionally, a signingTime
                           attribute is included with the response.

             2.c.2.b.3.b - Else if the signer is either a registered GLO
                           or the member, the GLA returns a
                           cMCStatusInfoExt.cMCStatus.success and a
                           signingTime attribute to the GLO (2 in Figure
                           6) if the GLO signed the request and to the
                           GL member (3 in Figure 6) if the GL member
                           signed the request.  The GLA also takes
                           administrative actions, which are beyond the
                           scope of this document, to delete the member
                           with the GL stored on the GLA.

               2.c.2.b.3.b.1 - The GLA applies confidentiality to the
                               response by encapsulating the
                               SignedData.PKIData in an EnvelopedData if
                               the request was encapsulated in an
                               EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

               2.c.2.b.3.b.2 - The GLA can also optionally apply another
                               SignedData over the EnvelopedData (see
                               <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   3 - Upon receipt of the cMCStatusInfoExt response, the GLO checks the
       signingTime and verifies the GLA signatures.  If an additional
       SignedData and/or EnvelopedData encapsulates the response (see
       <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GLO verifies the outer signature
       and/or decrypts the outer layer prior to verifying the signature
       on the innermost SignedData.

     3.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLO MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.

     3.b - Else if signature processing continues and if the signatures
           do verify, the GLO checks that one of the names in the
           certificate used to sign the response matches the name of the
           GL.






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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-55" ></span>
<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


       3.b.1 - If the name of the GL does not match the name present in
               the certificate used to sign the message, the GLO should
               not believe the response.

       3.b.2 - Else if the name of the GL matches the name present in
               the certificate and:

         3.b.2.a - If the signatures verify and the response is
                   cMCStatusInfoExt.cMCStatus.success, the GLO has
                   deleted the member from the GL.  If member was
                   deleted from a managed list and the original request
                   was signed by the member, the GLO sends a
                   cMCStatusInfoExt.cMCStatus.success and a signingTime
                   attribute to the GL member.

         3.b.2.b - Else if the GLO received a
                   cMCStatusInfoExt.cMCStatus.failed with any reason,
                   the GLO may reattempt to delete the member from the
                   GL using the information provided in the response.

   4 - Upon receipt of the cMCStatusInfoExt response, the member checks
       the signingTime and verifies the GLA signature(s) or GLO
       signature(s).  If an additional SignedData and/or EnvelopedData
       encapsulates the response (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GLO
       verifies the outer signature and/or decrypts the outer layer
       prior to verifying the signature on the innermost SignedData.

     4.a - If the signingTime attribute value is not within the locally
           accepted time window, the prospective member MAY return a
           response indicating cMCStatus.failed and
           otherInfo.failInfo.badTime and a signingTime attribute.

     4.b - Else if signature processing continues and if the signatures
           verify, the GL member checks that one of the names in the
           certificate used to sign the response matches the name of the
           GL.

       4.b.1 - If the name of the GL does not match the name present in
               the certificate used to sign the message, the GL member
               should not believe the response.

       4.b.2 - Else if the name of the GL matches the name present in
               the certificate and:

         4.b.2.a - If the signature(s) verify, the member has been
                   deleted from the GL.





<span class="grey">Turner                      Standards Track                    [Page 55]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-56" ></span>
<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


         4.b.2.b - Else if the member received a
                   cMCStatusInfoExt.cMCStatus.failed with any reason,
                   the member can reattempt to delete itself from the GL
                   using the information provided in the response.

<span class="h4"><a class="selflink" id="section-4.4.2" href="#section-4.4.2">4.4.2</a>.  Member Initiated Deletions</span>

   The process for member initiated deletion of its own membership using
   the glDeleteMember requests is as follows:

   1 - The member sends a
       SignedData.PKIData.controlSequence.glDeleteMember request to the
       GLA (A in Figure 6).  The member includes the name of the GL in
       glName and the member's own name in glMemberToDelete.  The GL
       member MUST also include the signingTime attribute with this
       request.

     1.a - The member can optionally apply confidentiality to the
           request by encapsulating the SignedData.PKIData in an
           EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

     1.b - The member can also optionally apply another SignedData over
           the EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   2 - Upon receipt of the request, the GLA verifies the request as per
       2 in <a href="#section-4.4.1">Section 4.4.1</a>.

   3 - Upon receipt of the forwarded request, the GLO checks the
       signingTime and verifies the member signature on the innermost
       SignedData.PKIData and the GLA signature on the outer layer.  If
       an EnvelopedData encapsulates the innermost layer (see <a href="#section-3.2.1.2">Section</a>
       <a href="#section-3.2.1.2">3.2.1.2</a> or 3.2.2), the GLO decrypts the outer layer prior to
       verifying the signature on the innermost SignedData.

       Note: For cases where the GL is closed and either (a) a
       prospective member sends directly to the GLO or (b) the GLA has
       mistakenly forwarded the request to the GLO, the GLO should first
       determine whether to honor the request.

     3.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLO MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.








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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-57" ></span>
<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


     3.b - Else if signature processing continues if the signatures
           cannot be verified, the GLO returns a cMCStatusInfoExt
           response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck and a signingTime
           attribute.

     3.c - Else if the signatures verify, the GLO checks to make sure
           one of the names in the certificates used to sign the request
           matches the name in glMemberToDelete.

       3.c.1 - If the names do not match, the GLO sends a
               SignedData.PKIResponse.controlSequence message back to
               the prospective member with
               cMCStatusInfoExt.cMCtatus.failed indicating why the
               prospective member was denied in
               cMCStatusInfoExt.statusString.  This stops people from
               adding people to GLs without their permission.
               Additionally, a signingTime attribute is included with
               the response.

       3.c.2 - Else if the names match, the GLO resubmits the
               glDeleteMember request (see <a href="#section-3.2.5">Section 3.2.5</a>) to the GLA (1
               in Figure 6).  The GLO makes sure the glMemberName is
               already on the GL.  The GLO also generates a glRekey
               request and include it with the GLDeleteMember request
               (see <a href="#section-4.5">Section 4.5</a>).

         3.c.2.a - The GLO applies confidentiality to the new
                   GLDeleteMember request by encapsulating the
                   SignedData.PKIData in an EnvelopedData if the initial
                   request was encapsulated in an EnvelopedData (see
                   <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

         3.c.2.b - The GLO can also optionally apply another SignedData
                   over the EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   4 - Further processing is as in 2 of <a href="#section-4.4.1">Section 4.4.1</a>.

<span class="h3"><a class="selflink" id="section-4.5" href="#section-4.5">4.5</a>.  Request Rekey of GL</span>

   From time to time, the GL will need to be rekeyed.  Some situations
   follow:

     - When a member is removed from a closed or managed GL.  In this
       case, the PKIData.controlSequence containing the glDeleteMember
       ought to contain a glRekey request.





<span class="grey">Turner                      Standards Track                    [Page 57]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-58" ></span>
<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


     - Depending on policy, when a member is removed from an unmanaged
       GL.  If the policy is to rekey the GL, the
       PKIData.controlSequence containing the glDeleteMember could also
       contain a glRekey request or an out-of-bands means could be used
       to tell the GLA to rekey the GL.  Rekeying of unmanaged GLs when
       members are deleted is not advised.

     - When the current shared KEK has been compromised.

     - When the current shared KEK is about to expire.  Consider two
       cases:

        -- If the GLO controls the GL rekey, the GLA should not assume
           that a new shared KEK should be distributed, but instead wait
           for the glRekey message.

        -- If the GLA controls the GL rekey, the GLA should initiate a
           glKey message as specified in <a href="#section-5">Section 5</a>.

   If the generationCounter (see <a href="#section-3.1.1">Section 3.1.1</a>) is set to a value
   greater than one (1) and the GLO controls the GL rekey, the GLO may
   generate a glRekey any time before the last shared KEK has expired.
   To be on the safe side, the GLO ought to request a rekey one (1)
   duration before the last shared KEK expires.

   The GLA and GLO are the only entities allowed to initiate a GL rekey.
   The GLO indicated whether they are going to control rekeys or whether
   the GLA is going to control rekeys when they assigned the shared KEK
   to GL (see <a href="#section-3.1.1">Section 3.1.1</a>).  The GLO initiates a GL rekey at any time.
   The GLA can be configured to automatically rekey the GL prior to the
   expiration of the shared KEK (the length of time before the
   expiration is an implementation decision).  The GLA can also
   automatically rekey GLs that have been compromised, but this is
   covered in <a href="#section-5">Section 5</a>.  Figure 7 depicts the protocol interactions to
   request a GL rekey.  Note that error messages are not depicted.
   Additionally, behavior for the optional transactionId, senderNonce,
   and recipientNonce CMC control attributes is not addressed in these
   procedures.

   +-----+  1   2,A  +-----+
   | GLA | &lt;-------&gt; | GLO |
   +-----+           +-----+

   Figure 7 - GL Rekey Request







<span class="grey">Turner                      Standards Track                    [Page 58]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-59" ></span>
<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


<span class="h4"><a class="selflink" id="section-4.5.1" href="#section-4.5.1">4.5.1</a>.  GLO Initiated Rekey Requests</span>

   The process for GLO initiated glRekey requests is as follows:

   1 - The GLO sends a SignedData.PKIData.controlSequence.glRekey
       request to the GLA (1 in Figure 7).  The GLO includes the glName.
       If glAdministration and glKeyNewAttributes are omitted then there
       is no change from the previously registered GL values for these
       fields.  If the GLO wants to force a rekey for all outstanding
       shared KEKs, it includes the glRekeyAllGLKeys set to TRUE.  The
       GLO MUST also include a signingTime attribute with this request.

     1.a - The GLO can optionally apply confidentiality to the request
           by encapsulating the SignedData.PKIData in an EnvelopedData
           (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

     1.b - The GLO can also optionally apply another SignedData over the
           EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   2 - Upon receipt of the request, the GLA checks the signingTime and
       verifies the signature on the innermost SignedData.PKIData.  If
       an additional SignedData and/or EnvelopedData encapsulates the
       request (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GLA verifies the
       outer signature and/or decrypts the outer layer prior to
       verifying the signature on the innermost SignedData.

     2.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLA MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.

     2.b - Else if signature processing continues and if the signatures
           do not verify, the GLA returns a cMCStatusInfoExt response
           indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.  Additionally, a
           signingTime attribute is included with the response.

     2.c - Else if the signatures do verify, the GLA makes sure the GL
           is supported by the GLA by checking that the glName matches a
           glName stored on the GLA.

       2.c.1 - If the glName present does not match a GL stored on the
               GLA, the GLA returns a response indicating
               cMCStatusInfoExt with cMCStatus.failed and
               otherInfo.extendedFailInfo.SKDFailInfo value of
               invalidGLName.  Additionally, a signingTime attribute is
               included with the response.




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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-60" ></span>
<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


       2.c.2 - Else if the glName present matches a GL stored on the
               GLA, the GLA checks that a registered GLO signed the
               request by checking that one of the names in the
               certificate used to sign the request is a registered GLO.

         2.c.2.a - If the names do not match, the GLA returns a response
                   indicating cMCStatusInfoExt with cMCStatus.failed and
                   otherInfo.extendedFailInfo.SKDFailInfo value of
                   noGLONameMatch.  Additionally, a signingTime
                   attribute is included with the response.

         2.c.2.b - Else if the names match, the GLA checks the
                   glNewKeyAttribute values.

           2.c.2.b.1 - If the new value for requestedAlgorithm is not
                       supported, the GLA returns a response indicating
                       cMCStatusInfoExt with cMCStatus.failed and
                       otherInfo.extendedFailInfo.SKDFailInfo value of
                       unsupportedAlgorithm.  Additionally, a
                       signingTime attribute is included with the
                       response.

           2.c.2.b.2 - Else if the new value duration is not supportable
                       (determining this is beyond the scope of this
                       document), the GLA returns a response indicating
                       cMCStatusInfoExt with cMCStatus.failed and
                       otherInfo.extendedFailInfo.SKDFailInfo value of
                       unsupportedDuration.  Additionally, a signingTime
                       attribute is included with the response.

           2.c.2.b.3 - Else if the GL is not supportable for other
                       reasons that the GLA does not wish to disclose,
                       the GLA returns a response indicating
                       cMCStatusInfoExt with cMCStatus.failed and
                       otherInfo.extendedFailInfo.SKDFailInfo value of
                       unspecified.  Additionally, a signingTime
                       attribute is included with the response.

           2.c.2.b.4 - Else if the new requestedAlgorithm and duration
                       are supportable or the glNewKeyAttributes was
                       omitted, the GLA returns a
                       cMCStatusInfoExt.cMCStatus.success and a
                       sigingTime attribute (2 in Figure 7).  The GLA
                       also uses the glKey message to distribute the
                       rekey shared KEK (see <a href="#section-5">Section 5</a>).






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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-61" ></span>
<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


             2.c.2.b.4.a - The GLA applies confidentiality to response
                           by encapsulating the SignedData.PKIData in an
                           EnvelopedData if the request was encapsulated
                           in an EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

             2.c.2.b.4.b - The GLA can also optionally apply another
                           SignedData over the EnvelopedData (see
                           <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   3 - Upon receipt of the cMCStatusInfoExt response, the GLO checks the
       signingTime and verifies the GLA signature(s).  If an additional
       SignedData and/or EnvelopedData encapsulates the forwarded
       response (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GLO verifies the
       outer signature and/or decrypts the forwarded response prior to
       verifying the signature on the innermost SignedData.

     3.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLA MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.

     3.b - Else if signature processing continues and if the signatures
           verify, the GLO checks that one of the names in the
           certificate used to sign the response matches the name of the
           GL.

       3.b.1 - If the name of the GL does not match the name present in
               the certificate used to sign the message, the GLO should
               not believe the response.

       3.b.2 - Else if the name of the GL matches the name present in
               the certificate and:

         3.b.2.a - If the signatures verify and the response is
                   cMCStatusInfoExt.cMCStatus.success, the GLO has
                   successfully rekeyed the GL.

         3.b.2.b - Else if the GLO received a
                   cMCStatusInfoExt.cMCStatus.failed with any reason,
                   the GLO can reattempt to rekey the GL using the
                   information provided in the response.










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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-62" ></span>
<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


<span class="h4"><a class="selflink" id="section-4.5.2" href="#section-4.5.2">4.5.2</a>.  GLA Initiated Rekey Requests</span>

   If the GLA is in charge of rekeying the GL the GLA will automatically
   issue a glKey message (see <a href="#section-5">Section 5</a>).  In addition the GLA will
   generate a cMCStatusInfoExt to indicate to the GL that a successful
   rekey has occurred.  The process for GLA initiated rekey is as
   follows:

   1 - The GLA generates for all GLOs a
       SignedData.PKIData.controlSequence.cMCStatusInfoExt.cMCStatus
       success and includes a signingTime attribute (A in Figure 7).

     1.a - The GLA can optionally apply confidentiality to the request
           by encapsulating the SignedData.PKIData in an EnvelopedData
           (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

     1.b - The GLA can also optionally apply another SignedData over the
           EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   2 - Upon receipt of the cMCStatusInfoExt.cMCStatus.success response,
       the GLO checks the signingTime and verifies the GLA signature(s).
       If an additional SignedData and/or EnvelopedData encapsulates the
       forwarded response (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GLO MUST
       verify the outer signature and/or decrypt the outer layer prior
       to verifying the signature on the innermost SignedData.

     2.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLO MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.

     2.b - Else if signature processing continues and if the signatures
           verify, the GLO checks that one of the names in the
           certificate used to sign the response matches the name of the
           GL.

       2.b.1 - If the name of the GL does not match the name present in
               the certificate used to sign the message, the GLO ought
               not believe the response.

       2.b.2 - Else if the name of the GL does match the name present in
               the certificate and the response is
               cMCStatusInfoExt.cMCStatus.success, the GLO knows the GLA
               has successfully rekeyed the GL.







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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-63" ></span>
<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


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

   Management of managed and closed GLs can become difficult for one GLO
   if the GL membership grows large.  To support distributing the
   workload, GLAs support having GLs be managed by multiple GLOs.  The
   glAddOwner and glRemoveOwner messages are designed to support adding
   and removing registered GLOs.  Figure 8 depicts the protocol
   interactions to send glAddOwner and glRemoveOwner messages and the
   resulting response messages.  Note that error messages are not shown.
   Additionally, behavior for the optional transactionId, senderNonce,
   and recipientNonce CMC control attributes is not addressed in these
   procedures.

        +-----+   1    2  +-----+
        | GLA | &lt;-------&gt; | GLO |
        +-----+           +-----+

   Figure 8 - GLO Add and Delete Owners

   The process for glAddOwner and glDeleteOwner is as follows:

   1 - The GLO sends a SignedData.PKIData.controlSequence.glAddOwner or
       glRemoveOwner request to the GLA (1 in Figure 8).  The GLO
       includes the GL name in glName, and the name and address of the
       GLO in glOwnerName and glOwnerAddress, respectively.  The GLO
       MUST also include the signingTime attribute with this request.

     1.a - The GLO can optionally apply confidentiality to the request
           by encapsulating the SignedData.PKIData in an EnvelopedData
           (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

     1.b - The GLO can also optionally apply another SignedData over the
           EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   2 - Upon receipt of the glAddOwner or glRemoveOwner request, the GLA
       checks the signingTime and verifies the GLO signature(s).  If an
       additional SignedData and/or EnvelopedData encapsulates the
       request (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GLA verifies the
       outer signature and/or decrypts the outer layer prior to
       verifying the signature on the innermost SignedData.

     2.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLA MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.






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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-64" ></span>
<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


     2.b - Else if signature processing continues and if the signatures
           cannot be verified, the GLA returns a cMCStatusInfoExt
           response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.  Additionally, a
           signingTime attribute is included with the response.

     2.c - Else if the signatures verify, the GLA makes sure the GL is
           supported by checking that the glName matches a glName stored
           on the GLA.

       2.c.1 - If the glName is not supported by the GLA, the GLA
               returns a response indicating cMCStatusInfoExt with
               cMCStatus.failed and
               otherInfo.extendedFailInfo.SKDFailInfo value of
               invalidGLName.  Additionally, a signingTime attribute is
               included with the response.

       2.c.2 - Else if the glName is supported by the GLA, the GLA
               ensures that a registered GLO signed the glAddOwner or
               glRemoveOwner request by checking that one of the names
               present in the digital signature certificate used to sign
               the glAddOwner or glDeleteOwner request matches the name
               of a registered GLO.

         2.c.2.a - If the names do not match, the GLA returns a response
                   indicating cMCStatusInfoExt with cMCStatus.failed and
                   otherInfo.extendedFailInfo.SKDFailInfo value of
                   noGLONameMatch.  Additionally, a signingTime
                   attribute is included with the response.

         2.c.2.b - Else if the names match, the GLA returns a
                   cMCStatusInfoExt.cMCStatus.success and a signingTime
                   attribute (2 in Figure 4).  The GLA also takes
                   administrative actions to associate the new
                   glOwnerName with the GL in the case of glAddOwner or
                   to disassociate the old glOwnerName with the GL in
                   the cased of glRemoveOwner.

           2.c.2.b.1 - The GLA applies confidentiality to the response
                       by encapsulating the SignedData.PKIResponse in an
                       EnvelopedData if the request was encapsulated in
                       an EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

           2.c.2.b.2 - The GLA can also optionally apply another
                       SignedData over the EnvelopedData (see <a href="#section-3.2.1.2">Section</a>
                       <a href="#section-3.2.1.2">3.2.1.2</a>).





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<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


   3 - Upon receipt of the cMCStatusInfoExt response, the GLO checks the
       signingTime and verifies the GLA's signature(s).  If an
       additional SignedData and/or EnvelopedData encapsulates the
       response (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GLO verifies the
       outer signature and/or decrypts the outer layer prior to
       verifying the signature on the innermost SignedData.

     3.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLO MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.

     3.b - Else if signature processing continues and if the signatures
           verify, the GLO checks that one of the names in the
           certificate used to sign the response matches the name of the
           GL.

       3.b.1 - If the name of the GL does not match the name present in
               the certificate used to sign the message, the GLO should
               not believe the response.

       3.b.2 - Else if the name of the GL does match the name present in
               the certificate and:

         3.b.2.a - If the signatures verify and the response was
                   cMCStatusInfoExt.cMCStatus.success, the GLO has
                   successfully added or removed the GLO.

         3.b.2.b - Else if the signatures verify and the response was
                   cMCStatusInfoExt.cMCStatus.failed with any reason,
                   the GLO can reattempt to add or delete the GLO using
                   the information provided in the response.

<span class="h3"><a class="selflink" id="section-4.7" href="#section-4.7">4.7</a>.  Indicate KEK Compromise</span>

   There will be times when the shared KEK is compromised.  GL members
   and GLOs use glkCompromise to tell the GLA that the shared KEK has
   been compromised.  Figure 9 depicts the protocol interactions for GL
   Key Compromise.  Note that error messages are not shown.
   Additionally, behavior for the optional transactionId, senderNonce,
   and recipientNonce CMC control attributes is not addressed in these
   procedures.









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   +-----+  2{1}                  4  +----------+
   | GLO | &lt;----------+    +-------&gt; | Member 1 |
   +-----+  5,3{1}    |    |         +----------+
   +-----+ &lt;----------+    |      4  +----------+
   | GLA |  1              +-------&gt; |   ...    |
   +-----+ &lt;---------------+         +----------+
                           |      4  +----------+
                           +-------&gt; | Member n |
                                     +----------+

   Figure 9 - GL Key Compromise

<span class="h4"><a class="selflink" id="section-4.7.1" href="#section-4.7.1">4.7.1</a>.  GL Member Initiated KEK Compromise Message</span>

   The process for GL member initiated glkCompromise messages is as
   follows:

   1 - The GL member sends a
       SignedData.PKIData.controlSequence.glkCompromise request to the
       GLA (1 in Figure 9).  The GL member includes the name of the GL
       in GeneralName.  The GL member MUST also include the signingTime
       attribute with this request.

     1.a - The GL member can optionally apply confidentiality to the
           request by encapsulating the SignedData.PKIData in an
           EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).  The glkCompromise can
           be included in an EnvelopedData generated with the
           compromised shared KEK.

     1.b - The GL member can also optionally apply another SignedData
           over the EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   2 - Upon receipt of the glkCompromise request, the GLA checks the
       signingTime and verifies the GL member signature(s).  If an
       additional SignedData and/or EnvelopedData encapsulates the
       request (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GLA verifies the
       outer signature and/or decrypts the outer layer prior to
       verifying the signature on the innermost SignedData.

     2.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLA MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.








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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-67" ></span>
<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


     2.b - Else if signature processing continues and if the signatures
           cannot be verified, the GLA returns a cMCStatusInfoExt
           response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.  Additionally, a
           signingTime attribute is included with the response.

     2.c - Else if the signatures verify, the GLA makes sure the GL is
           supported by checking that the indicated GL name matches a
           glName stored on the GLA.

       2.c.1 - If the glName is not supported by the GLA, the GLA
               returns a response indicating cMCStatusInfoExt with
               cMCStatus.failed and
               otherInfo.extendedFailInfo.SKDFailInfo value of
               invalidGLName.  Additionally, a signingTime attribute is
               included with the response.

       2.c.2 - Else if the glName is supported by the GLA, the GLA
               checks who signed the request.  For GLOs, one of the
               names in the certificate used to sign the request needs
               to match a registered GLO.  For the member, the name in
               glMember.glMemberName needs to match one of the names in
               the certificate used to sign the request.

         2.c.2.a - If the GLO signed the request, the GLA generates a
                   glKey message as described in <a href="#section-5">Section 5</a> to rekey the
                   GL (4 in Figure 9).

         2.c.2.b - Else if someone other than the GLO signed the
                   request, the GLA forwards the glkCompromise message
                   (see <a href="#section-3.2.3">Section 3.2.3</a>) to the GLO (2{1} in Figure 9).
                   If there is more than one GLO, to which GLO the
                   request is forwarded is beyond the scope of this
                   document.  Further processing by the GLO is discussed
                   in <a href="#section-4.7.2">Section 4.7.2</a>.

<span class="h4"><a class="selflink" id="section-4.7.2" href="#section-4.7.2">4.7.2</a>.  GLO Initiated KEK Compromise Message</span>

   The process for GLO initiated glkCompromise messages is as follows:

   1 - The GLO either:

     1.a - Generates the glkCompromise message itself by sending a
           SignedData.PKIData.controlSequence.glkCompromise request to
           the GLA (5 in Figure 9).  The GLO includes the name of the GL
           in GeneralName.  The GLO MUST also include a signingTime
           attribute with this request.




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<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


       1.a.1 - The GLO can optionally apply confidentiality to the
               request by encapsulating the SignedData.PKIData in an
               EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).  The glkCompromise
               can be included in an EnvelopedData generated with the
               compromised shared KEK.

       1.a.2 - The GLO can also optionally apply another SignedData over
               the EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

     1.b - Otherwise, checks the signingTime and verifies the GLA and GL
           member signatures on the forwarded glkCompromise message.  If
           an additional SignedData and/or EnvelopedData encapsulates
           the request (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GLO verifies
           the outer signature and/or decrypts the outer layer prior to
           verifying the signature on the innermost SignedData.

       1.b.1 - If the signingTime attribute value is not within the
               locally accepted time window, the GLO MAY return a
               response indicating cMCStatus.failed and
               otherInfo.failInfo.badTime and a signingTime attribute.

       1.b.2 - Else if signature processing continues and if the
               signatures cannot be verified, the GLO returns a
               cMCStatusInfoExt response indicating cMCStatus.failed and
               otherInfo.failInfo.badMessageCheck.  Additionally, a
               signingTime attribute is included with the response.

         1.b.2.a - If the signatures verify, the GLO checks that the
                   names in the certificate match the name of the signer
                   (i.e., the name in the certificate used to sign the
                   GL member's request is the GL member).

           1.b.2.a.1 - If either name does not match, the GLO ought not
                       trust the signer and it ought not forward the
                       message to the GLA.

           1.b.2.a.2 - Else if the names match and the signatures
                       verify, the GLO determines whether to forward the
                       glkCompromise message back to the GLA (3{1} in
                       Figure 9).  Further processing by the GLA is in 2
                       of <a href="#section-4.7.1">Section 4.7.1</a>.  The GLO can also return a
                       response to the prospective member with
                       cMCStatusInfoExt.cMCtatus.success indicating that
                       the glkCompromise message was successfully
                       received.






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<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


<span class="h3"><a class="selflink" id="section-4.8" href="#section-4.8">4.8</a>.  Request KEK Refresh</span>

   There will be times when GL members have irrecoverably lost their
   shared KEK.  The shared KEK is not compromised and a rekey of the
   entire GL is not necessary.  GL members use the glkRefresh message to
   request that the shared KEK(s) be redistributed to them.  Figure 10
   depicts the protocol interactions for GL Key Refresh.  Note that
   error messages are not shown.  Additionally, behavior for the
   optional transactionId, senderNonce, and recipientNonce CMC control
   attributes is not addressed in these procedures.

   +-----+   1       2   +----------+
   | GLA | &lt;-----------&gt; |  Member  |
   +-----+               +----------+

      Figure 10 - GL KEK Refresh

   The process for glkRefresh is as follows:

   1 - The GL member sends a
       SignedData.PKIData.controlSequence.glkRefresh request to the GLA
       (1 in Figure 10).  The GL member includes name of the GL in
       GeneralName.  The GL member MUST also include a signingTime
       attribute with this request.

     1.a - The GL member can optionally apply confidentiality to the
           request by encapsulating the SignedData.PKIData in an
           EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

     1.b - The GL member can also optionally apply another SignedData
           over the EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   2 - Upon receipt of the glkRefresh request, the GLA checks the
       signingTime and verifies the GL member signature(s).  If an
       additional SignedData and/or EnvelopedData encapsulates the
       request (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GLA verifies the
       outer signature and/or decrypt the outer layer prior to verifying
       the signature on the innermost SignedData.

     2.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLA MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.








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<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


     2.b - Else if signature processing continues and if the signatures
           cannot be verified, the GLA returns a cMCStatusInfoExt
           response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.  Additionally, a
           signingTime attribute is included with the response.

     2.c - Else if the signatures verify, the GLA makes sure the GL is
           supported by checking that the GLGeneralName matches a glName
           stored on the GLA.

       2.c.1 - If the name of the GL is not supported by the GLA, the
               GLA returns a response indicating cMCStatusInfoExt with
               cMCStatus.failed and
               otherInfo.extendedFailInfo.SKDFailInfo value of
               invalidGLName.  Additionally, a signingTime attribute is
               included with the response.

       2.c.2 - Else if the glName is supported by the GLA, the GLA
               ensures that the GL member is on the GL.

         2.c.2.a - If the glMemberName is not present on the GL, the GLA
                   returns a response indicating cMCStatusInfoExt with
                   cMCStatus.failed and
                   otherInfo.extendedFailInfo.SKDFailInfo value of
                   noSpam.  Additionally, a signingTime attribute is
                   included with the response.

         2.c.2.b - Else if the glMemberName is present on the GL, the
                   GLA returns a cMCStatusInfoExt.cMCStatus.success, a
                   signingTime attribute, and a glKey message (2 in
                   Figure 10) as described in <a href="#section-5">Section 5</a>.

<span class="h3"><a class="selflink" id="section-4.9" href="#section-4.9">4.9</a>.  GLA Query Request and Response</span>

   There will be certain times when a GLO is having trouble setting up a
   GL because it does not know the algorithm(s) or some other
   characteristic that the GLA supports.  There can also be times when
   prospective GL members or GL members need to know something about the
   GLA (these requests are not defined in the document).  The
   glaQueryRequest and glaQueryResponse messages have been defined to
   support determining this information.  Figure 11 depicts the protocol
   interactions for glaQueryRequest and glaQueryResponse.  Note that
   error messages are not shown.  Additionally, behavior for the
   optional transactionId, senderNonce, and recipientNonce CMC control
   attributes is not addressed in these procedures.






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<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


         +-----+   1    2  +------------------+
         | GLA | &lt;-------&gt; | GLO or GL Member |
         +-----+           +------------------+

   Figure 11 - GLA Query Request and Response

   The process for glaQueryRequest and glaQueryResponse is as follows:

   1 - The GLO, GL member, or prospective GL member sends a
       SignedData.PKIData.controlSequence.glaQueryRequest request to the
       GLA (1 in Figure 11).  The GLO, GL member, or prospective GL
       member indicates the information it is interested in receiving
       from the GLA.  Additionally, a signingTime attribute is included
       with this request.

     1.a - The GLO, GL member, or prospective GL member can optionally
           apply confidentiality to the request by encapsulating the
           SignedData.PKIData in an EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

     1.b - The GLO, GL member, or prospective GL member can also
           optionally apply another SignedData over the EnvelopedData
           (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   2 - Upon receipt of the glaQueryRequest, the GLA determines if it
       accepts glaQueryRequest messages.

     2.a - If the GLA does not accept glaQueryRequest messages, the GLA
           returns a cMCStatusInfoExt response indicating
           cMCStatus.noSupport and any other information in
           statusString.

     2.b - Else if the GLA does accept GLAQueryRequests, the GLA checks
           the signingTime and verifies the GLO, GL member, or
           prospective GL member signature(s).  If an additional
           SignedData and/or EnvelopedData encapsulates the request (see
           <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GLA verifies the outer
           signature and/or decrypts the outer layer prior to verifying
           the signature on the innermost SignedData.

       2.b.1 - If the signingTime attribute value is not within the
               locally accepted time window, the GLA MAY return a
               response indicating cMCStatus.failed and
               otherInfo.failInfo.badTime and a signingTime attribute.








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<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


       2.b.2 - Else if the signature processing continues and if the
               signatures cannot be verified, the GLA returns a
               cMCStatusInfoExt response indicating cMCStatus.failed and
               otherInfo.failInfo.badMessageCheck.  Additionally, a
               signingTime attribute is included with the response.

       2.b.3 - Else if the signatures verify, the GLA returns a
               glaQueryResponse (2 in Figure 11) with the correct
               response if the glaRequestType is supported or returns a
               cMCStatusInfoExt response indicating cMCStatus.noSupport
               if the glaRequestType is not supported.  Additionally, a
               signingTime attribute is included with the response.

         2.b.3.a - The GLA applies confidentiality to the response by
                   encapsulating the SignedData.PKIResponse in an
                   EnvelopedData if the request was encapsulated in an
                   EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

         2.b.3.b - The GLA can also optionally apply another SignedData
                   over the EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   3 - Upon receipt of the glaQueryResponse, the GLO, GL member, or
       prospective GL member checks the signingTime and verifies the GLA
       signature(s).  If an additional SignedData and/or EnvelopedData
       encapsulates the response (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the
       GLO, GL member, or prospective GL member verifies the outer
       signature and/or decrypts the outer layer prior to verifying the
       signature on the innermost SignedData.

     3.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLO, GL member, or prospective GL
           member MAY return a response indicating cMCStatus.failed and
           otherInfo.failInfo.badTime and a signingTime attribute.

     3.b - Else if signature processing continues and if the signatures
           do not verify, the GLO, GL member, or prospective GL member
           returns a cMCStatusInfoExt response indicating
           cMCStatus.failed and otherInfo.failInfo.badMessageCheck.
           Additionally, a signingTime attribute is included with the
           response.

     3.c - Else if the signatures verify, then the GLO, GL member, or
           prospective GL member checks that one of the names in the
           certificate used to sign the response matches the name of the
           GL.






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<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


       3.c.1 - If the name of the GL does not match the name present in
               the certificate used to sign the message, the GLO ought
               not believe the response.

       3.c.2 - Else if the name of the GL matches the name present in
               the certificate and the response was glaQueryResponse,
               then the GLO, GL member, or prospective GL member may use
               the information contained therein.

<span class="h3"><a class="selflink" id="section-4.10" href="#section-4.10">4.10</a>.  Update Member Certificate</span>

   When the GLO generates a glAddMember request, when the GLA generates
   a glKey message, or when the GLA processes a glAddMember, there can
   be instances when the GL member's certificate has expired or is
   invalid.  In these instances, the GLO or GLA may request that the GL
   member provide a new certificate to avoid the GLA from being unable
   to generate a glKey message for the GL member.  There might also be
   times when the GL member knows that its certificate is about to
   expire or has been revoked, and GL member will not be able to receive
   GL rekeys.  Behavior for the optional transactionId, senderNonce, and
   recipientNonce CMC control attributes is not addressed in these
   procedures.

<span class="h4"><a class="selflink" id="section-4.10.1" href="#section-4.10.1">4.10.1</a>.  GLO and GLA Initiated Update Member Certificate</span>

   The process for GLO initiated glUpdateCert is as follows:

   1 - The GLO or GLA sends a
       SignedData.PKIData.controlSequence.glProvideCert request to the
       GL member.  The GLO or GLA indicates the GL name in glName and
       the GL member name in glMemberName.  Additionally, a signingTime
       attribute is included with this request.

     1.a - The GLO or GLA can optionally apply confidentiality to the
           request by encapsulating the SignedData.PKIData in an
           EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).  If the GL member's PKC
           has been revoked, the GLO or GLA ought not use it to generate
           the EnvelopedData that encapsulates the glProvideCert
           request.

     1.b - The GLO or GLA can also optionally apply another SignedData
           over the EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).









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   2 - Upon receipt of the glProvideCert message, the GL member checks
       the signingTime and verifies the GLO or GLA signature(s).  If an
       additional SignedData and/or EnvelopedData encapsulates the
       response (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GL member verifies
       the outer signature and/or decrypts the outer layer prior to
       verifying the signature on the innermost SignedData.

     2.a - If the signingTime attribute value is not within the locally
           accepted time window, the GL member MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.

     2.b - Else if signature processing continues and if the signatures
           cannot be verified, the GL member returns a cMCStatusInfoExt
           response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.  Additionally, a
           signingTime attribute is included with the response.

     2.c - Else if the signatures verify, the GL member generates a
           Signed.PKIResponse.controlSequence.glUpdateCert that includes
           the GL name in glName, the member's name in
           glMember.glMemberName, the member's encryption certificate in
           glMember.certificates.pKC.  The GL member can also include
           any attribute certificates associated with the member's
           encryption certificate in glMember.certificates.aC, and the
           certification path associated with the member's encryption
           and attribute certificates in glMember.certificates.certPath.
           Additionally, a signingTime attribute is included with the
           response.

       2.c.1 - The GL member can optionally apply confidentiality to the
               request by encapsulating the SignedData.PKIResponse in an
               EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).  If the GL member's
               PKC has been revoked, the GL member ought not use it to
               generate the EnvelopedData that encapsulates the
               glProvideCert request.

       2.c.2 - The GL member can also optionally apply another
               SignedData over the EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   3 - Upon receipt of the glUpdateCert message, the GLO or GLA checks
       the signingTime and verifies the GL member signature(s).  If an
       additional SignedData and/or EnvelopedData encapsulates the
       response (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GL member verifies
       the outer signature and/or decrypts the outer layer prior to
       verifying the signature on the innermost SignedData.





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<span class="grey"><a href="./rfc5275">RFC 5275</a>                     CMS SymKeyDist                    June 2008</span>


     3.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLO or GLA MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.

     3.b - Else if signature processing continues and if the signatures
           cannot be verified, the GLO or GLA returns a cMCStatusInfoExt
           response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.  Additionally, a
           signingTime attribute is included with the response.

     3.c - Else if the signatures verify, the GLO or GLA verifies the
           member's encryption certificate.

       3.c.1 - If the member's encryption certificate cannot be
               verified, the GLO returns either another glProvideCert
               request or a cMCStatusInfoExt with cMCStatus.failed and
               the reason why in cMCStatus.statusString. glProvideCert
               should be returned only a certain number of times is
               because if the GL member does not have a valid
               certificate it will never be able to return one.
               Additionally, a signingTime attribute is included with
               either response.

       3.c.2 - Else if the member's encryption certificate cannot be
               verified, the GLA returns another glProvideCert request
               to the GL member or a cMCStatusInfoExt with
               cMCStatus.failed and the reason why in
               cMCStatus.statusString to the GLO. glProvideCert should
               be returned only a certain number of times because if the
               GL member does not have a valid certificate it will never
               be able to return one.  Additionally, a signingTime
               attribute is included with the response.

       3.c.3 - Else if the member's encryption certificate verifies, the
               GLO or GLA will use it in subsequent glAddMember requests
               and glKey messages associated with the GL member.

<span class="h4"><a class="selflink" id="section-4.10.2" href="#section-4.10.2">4.10.2</a>.  GL Member Initiated Update Member Certificate</span>

   The process for an unsolicited GL member glUpdateCert is as follows:

   1 - The GL member sends a Signed.PKIData.controlSequence.glUpdateCert
       that includes the GL name in glName, the member's name in
       glMember.glMemberName, the member's encryption certificate in
       glMember.certificates.pKC.  The GL member can also include any
       attribute certificates associated with the member's encryption
       certificate in glMember.certificates.aC, and the certification



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       path associated with the member's encryption and attribute
       certificates in glMember.certificates.certPath.  The GL member
       MUST also include a signingTime attribute with this request.

     1.a - The GL member can optionally apply confidentiality to the
           request by encapsulating the SignedData.PKIData in an
           EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).  If the GL member's PKC
           has been revoked, the GLO or GLA ought not use it to generate
           the EnvelopedData that encapsulates the glProvideCert
           request.

     1.b - The GL member can also optionally apply another SignedData
           over the EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   2 - Upon receipt of the glUpdateCert message, the GLA checks the
       signingTime and verifies the GL member signature(s).  If an
       additional SignedData and/or EnvelopedData encapsulates the
       response (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or 3.2.2), the GLA verifies the
       outer signature and/or decrypts the outer layer prior to
       verifying the signature on the innermost SignedData.

     2.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLA MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.

     2.b - Else if signature processing continues and if the signatures
           cannot be verified, the GLA returns a cMCStatusInfoExt
           response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.

     2.c - Else if the signatures verify, the GLA verifies the member's
           encryption certificate.

       2.c.1 - If the member's encryption certificate cannot be
               verified, the GLA returns another glProvideCert request
               to the GL member or a cMCStatusInfoExt with
               cMCStatus.failed and the reason why in
               cMCStatus.statusString to the GLO. glProvideCert ought
               not be returned indefinitely;  if the GL member does not
               have a valid certificate it will never be able to return
               one.  Additionally, a signingTime attribute is included
               with the response.

       2.c.2 - Else if the member's encryption certificate verifies, the
               GLA will use it in subsequent glAddMember requests and
               glKey messages associated with the GL member.  The GLA
               also forwards the glUpdateCert message to the GLO.



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<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>.  Distribution Message</span>

   The GLA uses the glKey message to distribute new, shared KEK(s) after
   receiving glAddMember, glDeleteMember (for closed and managed GLs),
   glRekey, glkCompromise, or glkRefresh requests and returning a
   cMCStatusInfoExt response for the respective request.  Figure 12
   depicts the protocol interactions to send out glKey messages.  Unlike
   the procedures defined for the administrative messages, the
   procedures defined in this section MUST be implemented by GLAs for
   origination and by GL members on reception.  Note that error messages
   are not shown.  Additionally, behavior for the optional
   transactionId, senderNonce, and recipientNonce CMC control attributes
   is not addressed in these procedures.

                     1   +----------+
               +-------&gt; | Member 1 |
               |         +----------+
   +-----+     |     1   +----------+
   | GLA | ----+-------&gt; |   ...    |
   +-----+     |         +----------+
               |     1   +----------+
               +-------&gt; | Member n |
                         +----------+

   Figure 12 - GL Key Distribution

   If the GL was set up with GLKeyAttributes.recipientsNotMutuallyAware
   set to TRUE, a separate glKey message MUST be sent to each GL member
   so as not to divulge information about the other GL members.

   When the glKey message is generated as a result of a:

     - glAddMember request,

     - glkComrpomise indication,

     - glkRefresh request,

     - glDeleteMember request with the GL's glAdministration set to
       managed or closed, and

     - glRekey request with generationCounter set to zero (0).

   The GLA MUST use either the kari (see Section 12.3.2 of [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>]) or
   ktri (see Section 12.3.1 of [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>]) choice in
   glKey.glkWrapped.RecipientInfo to ensure that only the intended
   recipients receive the shared KEK.  The GLA MUST support the ktri
   choice.



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   When the glKey message is generated as a result of a glRekey request
   with generationCounter greater than zero (0) or when the GLA controls
   rekeys, the GLA MAY use the kari, ktri, or kekri (see Section 12.3.3
   of [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>]) in glKey.glkWrapped.RecipientInfo to ensure that only the
   intended recipients receive the shared KEK.  The GLA MUST support the
   RecipientInfo.ktri choice.

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

   When a glKey message is generated, the process is as follows:

   1 - The GLA MUST send a SignedData.PKIData.controlSequence.glKey to
       each member by including glName, glIdentifier, glkWrapped,
       glkAlgorithm, glkNotBefore, and glkNotAfter.  If the GLA cannot
       generate a glKey message for the GL member because the GL
       member's PKC has expired or is otherwise invalid, the GLA MAY
       send a glUpdateCert to the GL member requesting a new certificate
       be provided (see <a href="#section-4.10">Section 4.10</a>).  The number of glKey messages
       generated for the GL is described in <a href="#section-3.1.13">Section 3.1.13</a>.
       Additionally, a signingTime attribute is included with the
       distribution message(s).

     1.a - The GLA MAY optionally apply another confidentiality layer to
           the message by encapsulating the SignedData.PKIData in
           another EnvelopedData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

     1.b - The GLA MAY also optionally apply another SignedData over the
           EnvelopedData.SignedData.PKIData (see <a href="#section-3.2.1.2">Section 3.2.1.2</a>).

   2 - Upon receipt of the glKey message, the GL members MUST check the
       signingTime and verify the signature over the innermost
       SignedData.PKIData.  If an additional SignedData and/or
       EnvelopedData encapsulates the message (see <a href="#section-3.2.1.2">Section 3.2.1.2</a> or
       3.2.2), the GL member MUST verify the outer signature and/or
       decrypt the outer layer prior to verifying the signature on the
       SignedData.PKIData.controlSequence.glKey.

     2.a - If the signingTime attribute value is not within the locally
           accepted time window, the GLA MAY return a response
           indicating cMCStatus.failed and otherInfo.failInfo.badTime
           and a signingTime attribute.

     2.b - Else if signature processing continues and if the signatures
           cannot be verified, the GL member MUST return a
           cMCStatusInfoExt response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.  Additionally, a
           signingTime attribute is included with the response.




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     2.c - Else if the signatures verify, the GL member processes the
           RecipientInfos according to [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>].  Once unwrapped, the GL
           member should store the shared KEK in a safe place.  When
           stored, the glName, glIdentifier, and shared KEK should be
           associated.  Additionally, the GL member MUST return a
           cMCStatusInfoExt indicating cMCStatus.success to tell the GLA
           the KEK was received.

<span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a>.  Algorithms</span>

   This section lists the algorithms that MUST be implemented.
   Additional algorithms that SHOULD be implemented are also included.
   Further algorithms MAY also be implemented.

<span class="h3"><a class="selflink" id="section-6.1" href="#section-6.1">6.1</a>.  KEK Generation Algorithm</span>

   Implementations MUST randomly generate content-encryption keys,
   message-authentication keys, initialization vectors (IVs), and
   padding.  Also, the generation of public/private key pairs relies on
   a random numbers.  The use of inadequate pseudo-random number
   generators (PRNGs) to generate cryptographic keys can result in
   little or no security.  An attacker may find it much easier to
   reproduce the PRNG environment that produced the keys, searching the
   resulting small set of possibilities, rather than brute force
   searching the whole key space.  The generation of quality random
   numbers is difficult.  <a href="./rfc4086">RFC 4086</a> [<a href="#ref-RANDOM" title="&quot;Randomness Requirements for Security&quot;">RANDOM</a>] offers important guidance in
   this area, and Appendix 3 of FIPS Pub 186 [<a href="#ref-FIPS" title="FIPS Pub 186-2: Digital Signature Standard">FIPS</a>] provides one quality
   PRNG technique.

<span class="h3"><a class="selflink" id="section-6.2" href="#section-6.2">6.2</a>.  Shared KEK Wrap Algorithm</span>

   In the mechanisms described in <a href="#section-5">Section 5</a>, the shared KEK being
   distributed in glkWrapped MUST be protected by a key of equal or
   greater length (e.g., if an AES 128-bit key is being distributed, a
   key of 128 bits or greater must be used to protect the key).

   The algorithm object identifiers included in glkWrapped are as
   specified in [<a href="#ref-CMSALG" title="&quot;Cryptographic Message Syntax (CMS) Algorithms&quot;">CMSALG</a>] and [<a href="#ref-CMSAES" title="&quot;Use of the Advanced Encryption Standard (AES) Encryption Algorithm in Cryptographic Message Syntax (CMS)&quot;">CMSAES</a>].

<span class="h3"><a class="selflink" id="section-6.3" href="#section-6.3">6.3</a>.  Shared KEK Algorithm</span>

   The shared KEK distributed and indicated in glkAlgorithm MUST support
   the symmetric key-encryption algorithms as specified in [<a href="#ref-CMSALG" title="&quot;Cryptographic Message Syntax (CMS) Algorithms&quot;">CMSALG</a>] and
   [<a href="#ref-CMSAES" title="&quot;Use of the Advanced Encryption Standard (AES) Encryption Algorithm in Cryptographic Message Syntax (CMS)&quot;">CMSAES</a>].







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<span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a>.  Message Transport</span>

   SMTP [<a href="#ref-SMTP" title="&quot;Simple Mail Transfer Protocol&quot;">SMTP</a>] MUST be supported.  Other transport mechanisms MAY also
   be supported.

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

   As GLOs control setting up and tearing down the GL and rekeying the
   GL, and can control member additions and deletions, GLOs play an
   important role in the management of the GL, and only "trusted" GLOs
   should be used.

   If a member is deleted or removed from a closed or a managed GL, the
   GL needs to be rekeyed.  If the GL is not rekeyed after a member is
   removed or deleted, the member still possesses the group key and will
   be able to continue to decrypt any messages that can be obtained.

   Members who store KEKs MUST associate the name of the GLA that
   distributed the key so that the members can make sure subsequent
   rekeys are originated from the same entity.

   When generating keys, care should be taken to ensure that the key
   size is not too small and duration too long because attackers will
   have more time to attack the key.  Key size should be selected to
   adequately protect sensitive business communications.

   GLOs and GLAs need to make sure that the generationCounter and
   duration are not too large.  For example, if the GLO indicates that
   the generationCounter is 14 and the duration is one year, then 14
   keys are generated each with a validity period of a year.  An
   attacker will have at least 13 years to attack the final key.

   Assume that two or more parties have a shared KEK, and the shared KEK
   is used to encrypt a second KEK for confidential distribution to
   those parties.  The second KEK might be used to encrypt a third KEK,
   the third KEK might be used to encrypt a fourth KEK, and so on.  If
   any of the KEKs in such a chain is compromised, all of the subsequent
   KEKs in the chain MUST also be considered compromised.

   An attacker can attack the group's shared KEK by attacking one
   member's copy of the shared KEK or attacking multiple members' copies
   of the shared KEK.  For the attacker, it may be easier to either
   attack the group member with the weakest security protecting its copy
   of the shared KEK or attack multiple group members.







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   An aggregation of the information gathered during the attack(s) may
   lead to the compromise of the group's shared KEK.  Mechanisms to
   protect the shared KEK should be commensurate with value of the data
   being protected.

   The nonce and signingTime attributes are used to protect against
   replay attacks.  However, these provisions are only helpful if
   entities maintain state information about the messages they have sent
   or received for comparison.  If sufficient information is not
   maintained on each exchange, nonces and signingTime are not helpful.
   Local policy determines the amount and duration of state information
   that is maintained.  Additionally, without a unified time source,
   there is the possibility of clocks drifting.  Local policy determines
   the acceptable difference between the local time and signingTime,
   which must compensate for unsynchronized clocks.  Implementations
   MUST handle messages with siginingTime attributes that indicate they
   were created in the future.

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

   Thanks to Russ Housley and Jim Schaad for providing much of the
   background and review required to write this document.

<span class="h2"><a class="selflink" id="section-10" href="#section-10">10</a>.  References</span>

<span class="h3"><a class="selflink" id="section-10.1" href="#section-10.1">10.1</a>.  Normative References</span>

   [<a id="ref-RFC2119">RFC2119</a>]    Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", <a href="https://www.rfc-editor.org/bcp/bcp14">BCP 14</a>, <a href="./rfc2119">RFC 2119</a>, March 1997.

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

   [<a id="ref-CMC">CMC</a>]        Schaad, J. and M. Myers, "Certificate Management over
                CMS (CMC)", <a href="./rfc5272">RFC 5272</a>, June 2008.

   [<a id="ref-PROFILE">PROFILE</a>]    Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
                Housley, R., and W. Polk, "Internet X.509 Public Key
                Infrastructure Certificate and Certificate Revocation
                List (CRL) Profile", <a href="./rfc5280">RFC 5280</a>, May 2008.

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







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

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

   [<a id="ref-CMSAES">CMSAES</a>]     Schaad, J., "Use of the Advanced Encryption Standard
                (AES) Encryption Algorithm in Cryptographic Message
                Syntax (CMS)", <a href="./rfc3565">RFC 3565</a>, July 2003.

   [<a id="ref-SMTP">SMTP</a>]       Klensin, J., Ed., "Simple Mail Transfer Protocol", <a href="./rfc2821">RFC</a>
                <a href="./rfc2821">2821</a>, April 2001.

<span class="h3"><a class="selflink" id="section-10.2" href="#section-10.2">10.2</a>.  Informative References</span>

   [<a id="ref-X400TRANS">X400TRANS</a>]  Hoffman, P. and C. Bonatti, "Transporting
                Secure/Multipurpose Internet Mail Extensions (S/MIME)
                Objects in X.400", <a href="./rfc3855">RFC 3855</a>, July 2004.

   [<a id="ref-RANDOM">RANDOM</a>]     Eastlake, D., 3rd, Schiller, J., and S. Crocker,
                "Randomness Requirements for Security", <a href="https://www.rfc-editor.org/bcp/bcp106">BCP 106</a>, <a href="./rfc4086">RFC</a>
                <a href="./rfc4086">4086</a>, June 2005.

   [<a id="ref-FIPS">FIPS</a>]       National Institute of Standards and Technology, FIPS Pub
                186-2: Digital Signature Standard, January 2000.






















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<span class="h2"><a class="selflink" id="appendix-A" href="#appendix-A">Appendix A</a>.  ASN.1 Module</span>

   SMIMESymmetricKeyDistribution
     { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
       pkcs-9(9) smime(16) modules(0) symkeydist(12) }

   DEFINITIONS IMPLICIT TAGS ::=
   BEGIN

   -- EXPORTS All --
   -- The types and values defined in this module are exported for use
   -- in the other ASN.1 modules.  Other applications may use them for
   -- their own purposes.

   IMPORTS

   -- PKIX Part 1 - Implicit [<a href="#ref-PROFILE" title="&quot;Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile&quot;">PROFILE</a>]
      GeneralName
        FROM PKIX1Implicit88 { iso(1) identified-organization(3) dod(6)
             internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
             id-pkix1-implicit(19) }

   -- PKIX Part 1 - Explicit [<a href="#ref-PROFILE" title="&quot;Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile&quot;">PROFILE</a>]
      AlgorithmIdentifier, Certificate
        FROM PKIX1Explicit88 { iso(1) identified-organization(3) dod(6)
             internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
             id-pkix1-explicit(18) }

   -- Cryptographic Message Syntax [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>]
      RecipientInfos, KEKIdentifier, CertificateSet
        FROM CryptographicMessageSyntax2004 {iso(1) member-body(2)
          us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) modules(0)
          cms-2004(24) }

   -- Advanced Encryption Standard (AES) with CMS [<a href="#ref-CMSAES" title="&quot;Use of the Advanced Encryption Standard (AES) Encryption Algorithm in Cryptographic Message Syntax (CMS)&quot;">CMSAES</a>]
      id-aes128-wrap
        FROM CMSAesRsaesOaep { iso(1) member-body(2) us(840)
          rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) modules(0)
          id-mod-cms-aes(19) }

   -- Attribute Certificate Profile [<a href="#ref-ACPROF" title="&quot;An Internet Attribute Certificate Profile for Authorization&quot;">ACPROF</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) };






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   -- This defines the GL symmetric key distribution object identifier
   -- arc.

   id-skd OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
     rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) skd(8) }

   -- This defines the GL Use KEK control attribute.

   id-skd-glUseKEK OBJECT IDENTIFIER ::= { id-skd 1 }

   GLUseKEK ::= SEQUENCE {
     glInfo                GLInfo,
     glOwnerInfo           SEQUENCE SIZE (1..MAX) OF GLOwnerInfo,
     glAdministration      GLAdministration DEFAULT 1,
     glKeyAttributes       GLKeyAttributes OPTIONAL }

   GLInfo ::= SEQUENCE {
     glName     GeneralName,
     glAddress  GeneralName }

   GLOwnerInfo ::= SEQUENCE {
     glOwnerName     GeneralName,
     glOwnerAddress  GeneralName,
     certificates    Certificates OPTIONAL }

   GLAdministration ::= INTEGER {
     unmanaged  (0),
     managed    (1),
     closed     (2) }

   GLKeyAttributes ::= SEQUENCE {
     rekeyControlledByGLO       [0] BOOLEAN DEFAULT FALSE,
     recipientsNotMutuallyAware [1] BOOLEAN DEFAULT TRUE,
     duration                   [2] INTEGER DEFAULT 0,
     generationCounter          [3] INTEGER DEFAULT 2,
     requestedAlgorithm         [4] AlgorithmIdentifier
                                 DEFAULT { id-aes128-wrap } }

   -- This defines the Delete GL control attribute.
   -- It has the simple type GeneralName.

   id-skd-glDelete OBJECT IDENTIFIER ::= { id-skd 2 }

   DeleteGL ::= GeneralName

   -- This defines the Add GL Member control attribute.

   id-skd-glAddMember OBJECT IDENTIFIER ::= { id-skd 3 }



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   GLAddMember ::= SEQUENCE {
     glName    GeneralName,
     glMember  GLMember }

   GLMember ::= SEQUENCE {
     glMemberName     GeneralName,
     glMemberAddress  GeneralName OPTIONAL,
     certificates     Certificates OPTIONAL }

   Certificates ::= SEQUENCE {
      pKC                [0] Certificate OPTIONAL,
                                  -- See [<a href="#ref-PROFILE" title="&quot;Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile&quot;">PROFILE</a>]
      aC                 [1] SEQUENCE SIZE (1.. MAX) OF
                             AttributeCertificate OPTIONAL,
                                  -- See [<a href="#ref-ACPROF" title="&quot;An Internet Attribute Certificate Profile for Authorization&quot;">ACPROF</a>]
      certPath           [2] CertificateSet OPTIONAL }
                                  -- From [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>]

   -- This defines the Delete GL Member control attribute.

   id-skd-glDeleteMember OBJECT IDENTIFIER ::= { id-skd 4 }

   GLDeleteMember ::= SEQUENCE {
     glName            GeneralName,
     glMemberToDelete  GeneralName }

   -- This defines the Delete GL Member control attribute.

   id-skd-glRekey OBJECT IDENTIFIER ::= { id-skd 5 }

   GLRekey ::= SEQUENCE {
     glName              GeneralName,
     glAdministration    GLAdministration OPTIONAL,
     glNewKeyAttributes  GLNewKeyAttributes OPTIONAL,
     glRekeyAllGLKeys    BOOLEAN OPTIONAL }

   GLNewKeyAttributes ::= SEQUENCE {
     rekeyControlledByGLO       [0] BOOLEAN OPTIONAL,
     recipientsNotMutuallyAware [1] BOOLEAN OPTIONAL,
     duration                   [2] INTEGER OPTIONAL,
     generationCounter          [3] INTEGER OPTIONAL,
     requestedAlgorithm         [4] AlgorithmIdentifier OPTIONAL }

   -- This defines the Add and Delete GL Owner control attributes.

   id-skd-glAddOwner OBJECT IDENTIFIER ::= { id-skd 6 }
   id-skd-glRemoveOwner OBJECT IDENTIFIER ::= { id-skd 7 }



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   GLOwnerAdministration ::= SEQUENCE {
     glName       GeneralName,
     glOwnerInfo  GLOwnerInfo }

   -- This defines the GL Key Compromise control attribute.
   -- It has the simple type GeneralName.

   id-skd-glKeyCompromise OBJECT IDENTIFIER ::= { id-skd 8 }

   GLKCompromise ::= GeneralName

   -- This defines the GL Key Refresh control attribute.

   id-skd-glkRefresh OBJECT IDENTIFIER ::= { id-skd 9 }

   GLKRefresh ::= SEQUENCE {
      glName  GeneralName,
      dates   SEQUENCE SIZE (1..MAX) OF Date }

   Date ::= SEQUENCE {
     start GeneralizedTime,
     end   GeneralizedTime OPTIONAL }

   -- This defines the GLA Query Request control attribute.

   id-skd-glaQueryRequest OBJECT IDENTIFIER ::= { id-skd 11 }

   GLAQueryRequest ::= SEQUENCE {
     glaRequestType   OBJECT IDENTIFIER,
     glaRequestValue  ANY DEFINED BY glaRequestType }


   -- This defines the GLA Query Response control attribute.

   id-skd-glaQueryResponse OBJECT IDENTIFIER ::= { id-skd 12 }

   GLAQueryResponse ::= SEQUENCE {
     glaResponseType   OBJECT IDENTIFIER,
     glaResponseValue  ANY DEFINED BY glaResponseType }

   -- This defines the GLA Request/Response (glaRR) arc for
   -- glaRequestType/glaResponseType.

   id-cmc-glaRR OBJECT IDENTIFIER ::= { iso(1)
     identified-organization(3) dod(6) internet(1) security(5)
     mechanisms(5) pkix(7) cmc(7) glaRR(99) }




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   -- This defines the Algorithm Request.

   id-cmc-gla-skdAlgRequest OBJECT IDENTIFIER ::= { id-cmc-glaRR 1 }

   SKDAlgRequest ::= NULL

   -- This defines the Algorithm Response.

   id-cmc-gla-skdAlgResponse OBJECT IDENTIFIER ::= { id-cmc-glaRR 2 }

   -- Note that the response for algorithmSupported request is the
   -- smimeCapabilities attribute as defined in MsgSpec [<a href="#ref-MSG" title="&quot;Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1 Message Specification&quot;">MSG</a>].
   -- This defines the control attribute to request an updated
   -- certificate to the GLA.

   id-skd-glProvideCert OBJECT IDENTIFIER ::= { id-skd 13 }

   GLManageCert ::= SEQUENCE {
     glName    GeneralName,
     glMember  GLMember }

   -- This defines the control attribute to return an updated
   -- certificate to the GLA.  It has the type GLManageCert.

   id-skd-glManageCert OBJECT IDENTIFIER ::= { id-skd 14 }

   -- This defines the control attribute to distribute the GL shared
   -- KEK.

   id-skd-glKey OBJECT IDENTIFIER ::= { id-skd 15 }

   GLKey ::= SEQUENCE {
     glName        GeneralName,
     glIdentifier  KEKIdentifier,  -- See [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>]
     glkWrapped    RecipientInfos,      -- See [<a href="#ref-CMS" title="&quot;Cryptographic Message Syntax (CMS)&quot;">CMS</a>]
     glkAlgorithm  AlgorithmIdentifier,
     glkNotBefore  GeneralizedTime,
     glkNotAfter   GeneralizedTime }

   -- This defines the CMC error types.

   id-cet-skdFailInfo  OBJECT IDENTIFIER ::= { iso(1)
     identified-organization(3) dod(6) internet(1) security(5)
     mechanisms(5) pkix(7) cet(15) skdFailInfo(1) }







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   SKDFailInfo ::= INTEGER {
     unspecified           (0),
     closedGL              (1),
     unsupportedDuration   (2),
     noGLACertificate      (3),
     invalidCert           (4),
     unsupportedAlgorithm  (5),
     noGLONameMatch        (6),
     invalidGLName         (7),
     nameAlreadyInUse      (8),
     noSpam                (9),
   -- obsolete             (10),
     alreadyAMember        (11),
     notAMember            (12),
     alreadyAnOwner        (13),
     notAnOwner            (14) }

   END -- SMIMESymmetricKeyDistribution

Author's Address

   Sean Turner
   IECA, Inc.
   3057 Nutley Street, Suite 106
   Fairfax, VA 22031
   USA

   EMail: turners@ieca.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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</pre>