File: rfc9266.html

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<!DOCTYPE html>
<html lang="en" class="RFC">
<head>
<meta charset="utf-8">
<meta content="Common,Latin" name="scripts">
<meta content="initial-scale=1.0" name="viewport">
<title>RFC 9266: Channel Bindings for TLS 1.3</title>
<meta content="Sam Whited" name="author">
<meta content='
       
        This document defines a channel binding type, tls-exporter, that is
        compatible with TLS 1.3 in accordance with RFC 5056, "On the Use of
        Channel Bindings to Secure Channels".  Furthermore, it updates the
        default channel binding to the new binding for versions of TLS greater
        than 1.2.  This document updates RFCs 5801, 5802, 5929, and 7677.
       
    ' name="description">
<meta content="xml2rfc 3.12.10" name="generator">
<meta content="9266" name="rfc.number">
<!-- Generator version information:
  xml2rfc 3.12.10
    Python 3.6.15
    appdirs 1.4.4
    ConfigArgParse 1.4.1
    google-i18n-address 2.4.0
    html5lib 1.0.1
    intervaltree 3.0.2
    Jinja2 2.11.3
    kitchen 1.2.6
    lxml 4.7.1
    MarkupSafe 2.0.1
    pycairo 1.15.1
    pycountry 19.8.18
    pyflakes 2.1.1
    PyYAML 5.4.1
    requests 2.24.0
    setuptools 40.5.0
    six 1.14.0
    WeasyPrint 52.5
-->
<link href="rfc9266.xml" rel="alternate" type="application/rfc+xml">
<link href="#copyright" rel="license">
<style type="text/css">/*

  NOTE: Changes at the bottom of this file overrides some earlier settings.

  Once the style has stabilized and has been adopted as an official RFC style,
  this can be consolidated so that style settings occur only in one place, but
  for now the contents of this file consists first of the initial CSS work as
  provided to the RFC Formatter (xml2rfc) work, followed by itemized and
  commented changes found necssary during the development of the v3
  formatters.

*/

/* fonts */
@import url('https://fonts.googleapis.com/css?family=Noto+Sans'); /* Sans-serif */
@import url('https://fonts.googleapis.com/css?family=Noto+Serif'); /* Serif (print) */
@import url('https://fonts.googleapis.com/css?family=Roboto+Mono'); /* Monospace */

@viewport {
  zoom: 1.0;
  width: extend-to-zoom;
}
@-ms-viewport {
  width: extend-to-zoom;
  zoom: 1.0;
}
/* general and mobile first */
html {
}
body {
  max-width: 90%;
  margin: 1.5em auto;
  color: #222;
  background-color: #fff;
  font-size: 14px;
  font-family: 'Noto Sans', Arial, Helvetica, sans-serif;
  line-height: 1.6;
  scroll-behavior: smooth;
}
.ears {
  display: none;
}

/* headings */
#title, h1, h2, h3, h4, h5, h6 {
  margin: 1em 0 0.5em;
  font-weight: bold;
  line-height: 1.3;
}
#title {
  clear: both;
  border-bottom: 1px solid #ddd;
  margin: 0 0 0.5em 0;
  padding: 1em 0 0.5em;
}
.author {
  padding-bottom: 4px;
}
h1 {
  font-size: 26px;
  margin: 1em 0;
}
h2 {
  font-size: 22px;
  margin-top: -20px;  /* provide offset for in-page anchors */
  padding-top: 33px;
}
h3 {
  font-size: 18px;
  margin-top: -36px;  /* provide offset for in-page anchors */
  padding-top: 42px;
}
h4 {
  font-size: 16px;
  margin-top: -36px;  /* provide offset for in-page anchors */
  padding-top: 42px;
}
h5, h6 {
  font-size: 14px;
}
#n-copyright-notice {
  border-bottom: 1px solid #ddd;
  padding-bottom: 1em;
  margin-bottom: 1em;
}
/* general structure */
p {
  padding: 0;
  margin: 0 0 1em 0;
  text-align: left;
}
div, span {
  position: relative;
}
div {
  margin: 0;
}
.alignRight.art-text {
  background-color: #f9f9f9;
  border: 1px solid #eee;
  border-radius: 3px;
  padding: 1em 1em 0;
  margin-bottom: 1.5em;
}
.alignRight.art-text pre {
  padding: 0;
}
.alignRight {
  margin: 1em 0;
}
.alignRight > *:first-child {
  border: none;
  margin: 0;
  float: right;
  clear: both;
}
.alignRight > *:nth-child(2) {
  clear: both;
  display: block;
  border: none;
}
svg {
  display: block;
}
.alignCenter.art-text {
  background-color: #f9f9f9;
  border: 1px solid #eee;
  border-radius: 3px;
  padding: 1em 1em 0;
  margin-bottom: 1.5em;
}
.alignCenter.art-text pre {
  padding: 0;
}
.alignCenter {
  margin: 1em 0;
}
.alignCenter > *:first-child {
  border: none;
  margin: 0 auto;
}

/* lists */
ol, ul {
  padding: 0;
  margin: 0 0 1em 2em;
}
ol ol, ul ul, ol ul, ul ol {
  margin-left: 1em;
}
li {
  margin: 0 0 0.25em 0;
}
.ulCompact li {
  margin: 0;
}
ul.empty, .ulEmpty {
  list-style-type: none;
}
ul.empty li, .ulEmpty li {
  margin-top: 0.5em;
}
ul.ulBare, li.ulBare {
  margin-left: 0em !important;
}
ul.compact, .ulCompact,
ol.compact, .olCompact {
  line-height: 100%;
  margin: 0 0 0 2em;
}

/* definition lists */
dl {
}
dl > dt {
  float: left;
  margin-right: 1em;
}
/* 
dl.nohang > dt {
  float: none;
}
*/
dl > dd {
  margin-bottom: .8em;
  min-height: 1.3em;
}
dl.compact > dd, .dlCompact > dd {
  margin-bottom: 0em;
}
dl > dd > dl {
  margin-top: 0.5em;
  margin-bottom: 0em;
}

/* links */
a {
  text-decoration: none;
}
a[href] {
  color: #22e; /* Arlen: WCAG 2019 */
}
a[href]:hover {
  background-color: #f2f2f2;
}
figcaption a[href],
a[href].selfRef {
  color: #222;
}
/* XXX probably not this:
a.selfRef:hover {
  background-color: transparent;
  cursor: default;
} */

/* Figures */
tt, code, pre, code {
  background-color: #f9f9f9;
  font-family: 'Roboto Mono', monospace;
}
pre {
  border: 1px solid #eee;
  margin: 0;
  padding: 1em;
}
img {
  max-width: 100%;
}
figure {
  margin: 0;
}
figure blockquote {
  margin: 0.8em 0.4em 0.4em;
}
figcaption {
  font-style: italic;
  margin: 0 0 1em 0;
}
@media screen {
  pre {
    overflow-x: auto;
    max-width: 100%;
    max-width: calc(100% - 22px);
  }
}

/* aside, blockquote */
aside, blockquote {
  margin-left: 0;
  padding: 1.2em 2em;
}
blockquote {
  background-color: #f9f9f9;
  color: #111; /* Arlen: WCAG 2019 */
  border: 1px solid #ddd;
  border-radius: 3px;
  margin: 1em 0;
}
cite {
  display: block;
  text-align: right;
  font-style: italic;
}

/* tables */
table {
  width: 100%;
  margin: 0 0 1em;
  border-collapse: collapse;
  border: 1px solid #eee;
}
th, td {
  text-align: left;
  vertical-align: top;
  padding: 0.5em 0.75em;
}
th {
  text-align: left;
  background-color: #e9e9e9;
}
tr:nth-child(2n+1) > td {
  background-color: #f5f5f5;
}
table caption {
  font-style: italic;
  margin: 0;
  padding: 0;
  text-align: left;
}
table p {
  /* XXX to avoid bottom margin on table row signifiers. If paragraphs should
     be allowed within tables more generally, it would be far better to select on a class. */
  margin: 0;
}

/* pilcrow */
a.pilcrow {
  color: #666; /* Arlen: AHDJ 2019 */
  text-decoration: none;
  visibility: hidden;
  user-select: none;
  -ms-user-select: none;
  -o-user-select:none;
  -moz-user-select: none;
  -khtml-user-select: none;
  -webkit-user-select: none;
  -webkit-touch-callout: none;
}
@media screen {
  aside:hover > a.pilcrow,
  p:hover > a.pilcrow,
  blockquote:hover > a.pilcrow,
  div:hover > a.pilcrow,
  li:hover > a.pilcrow,
  pre:hover > a.pilcrow {
    visibility: visible;
  }
  a.pilcrow:hover {
    background-color: transparent;
  }
}

/* misc */
hr {
  border: 0;
  border-top: 1px solid #eee;
}
.bcp14 {
  font-variant: small-caps;
}

.role {
  font-variant: all-small-caps;
}

/* info block */
#identifiers {
  margin: 0;
  font-size: 0.9em;
}
#identifiers dt {
  width: 3em;
  clear: left;
}
#identifiers dd {
  float: left;
  margin-bottom: 0;
}
/* Fix PDF info block run off issue */
@media print {
  #identifiers dd {
    float: none;
  }
}
#identifiers .authors .author {
  display: inline-block;
  margin-right: 1.5em;
}
#identifiers .authors .org {
  font-style: italic;
}

/* The prepared/rendered info at the very bottom of the page */
.docInfo {
  color: #666; /* Arlen: WCAG 2019 */
  font-size: 0.9em;
  font-style: italic;
  margin-top: 2em;
}
.docInfo .prepared {
  float: left;
}
.docInfo .prepared {
  float: right;
}

/* table of contents */
#toc  {
  padding: 0.75em 0 2em 0;
  margin-bottom: 1em;
}
nav.toc ul {
  margin: 0 0.5em 0 0;
  padding: 0;
  list-style: none;
}
nav.toc li {
  line-height: 1.3em;
  margin: 0.75em 0;
  padding-left: 1.2em;
  text-indent: -1.2em;
}
/* references */
.references dt {
  text-align: right;
  font-weight: bold;
  min-width: 7em;
}
.references dd {
  margin-left: 8em;
  overflow: auto;
}

.refInstance {
  margin-bottom: 1.25em;
}

.references .ascii {
  margin-bottom: 0.25em;
}

/* index */
.index ul {
  margin: 0 0 0 1em;
  padding: 0;
  list-style: none;
}
.index ul ul {
  margin: 0;
}
.index li {
  margin: 0;
  text-indent: -2em;
  padding-left: 2em;
  padding-bottom: 5px;
}
.indexIndex {
  margin: 0.5em 0 1em;
}
.index a {
  font-weight: 700;
}
/* make the index two-column on all but the smallest screens */
@media (min-width: 600px) {
  .index ul {
    -moz-column-count: 2;
    -moz-column-gap: 20px;
  }
  .index ul ul {
    -moz-column-count: 1;
    -moz-column-gap: 0;
  }
}

/* authors */
address.vcard {
  font-style: normal;
  margin: 1em 0;
}

address.vcard .nameRole {
  font-weight: 700;
  margin-left: 0;
}
address.vcard .label {
  font-family: "Noto Sans",Arial,Helvetica,sans-serif;
  margin: 0.5em 0;
}
address.vcard .type {
  display: none;
}
.alternative-contact {
  margin: 1.5em 0 1em;
}
hr.addr {
  border-top: 1px dashed;
  margin: 0;
  color: #ddd;
  max-width: calc(100% - 16px);
}

/* temporary notes */
.rfcEditorRemove::before {
  position: absolute;
  top: 0.2em;
  right: 0.2em;
  padding: 0.2em;
  content: "The RFC Editor will remove this note";
  color: #9e2a00; /* Arlen: WCAG 2019 */
  background-color: #ffd; /* Arlen: WCAG 2019 */
}
.rfcEditorRemove {
  position: relative;
  padding-top: 1.8em;
  background-color: #ffd; /* Arlen: WCAG 2019 */
  border-radius: 3px;
}
.cref {
  background-color: #ffd; /* Arlen: WCAG 2019 */
  padding: 2px 4px;
}
.crefSource {
  font-style: italic;
}
/* alternative layout for smaller screens */
@media screen and (max-width: 1023px) {
  body {
    padding-top: 2em;
  }
  #title {
    padding: 1em 0;
  }
  h1 {
    font-size: 24px;
  }
  h2 {
    font-size: 20px;
    margin-top: -18px;  /* provide offset for in-page anchors */
    padding-top: 38px;
  }
  #identifiers dd {
    max-width: 60%;
  }
  #toc {
    position: fixed;
    z-index: 2;
    top: 0;
    right: 0;
    padding: 0;
    margin: 0;
    background-color: inherit;
    border-bottom: 1px solid #ccc;
  }
  #toc h2 {
    margin: -1px 0 0 0;
    padding: 4px 0 4px 6px;
    padding-right: 1em;
    min-width: 190px;
    font-size: 1.1em;
    text-align: right;
    background-color: #444;
    color: white;
    cursor: pointer;
  }
  #toc h2::before { /* css hamburger */
    float: right;
    position: relative;
    width: 1em;
    height: 1px;
    left: -164px;
    margin: 6px 0 0 0;
    background: white none repeat scroll 0 0;
    box-shadow: 0 4px 0 0 white, 0 8px 0 0 white;
    content: "";
  }
  #toc nav {
    display: none;
    padding: 0.5em 1em 1em;
    overflow: auto;
    height: calc(100vh - 48px);
    border-left: 1px solid #ddd;
  }
}

/* alternative layout for wide screens */
@media screen and (min-width: 1024px) {
  body {
    max-width: 724px;
    margin: 42px auto;
    padding-left: 1.5em;
    padding-right: 29em;
  }
  #toc {
    position: fixed;
    top: 42px;
    right: 42px;
    width: 25%;
    margin: 0;
    padding: 0 1em;
    z-index: 1;
  }
  #toc h2 {
    border-top: none;
    border-bottom: 1px solid #ddd;
    font-size: 1em;
    font-weight: normal;
    margin: 0;
    padding: 0.25em 1em 1em 0;
  }
  #toc nav {
    display: block;
    height: calc(90vh - 84px);
    bottom: 0;
    padding: 0.5em 0 0;
    overflow: auto;
  }
  img { /* future proofing */
    max-width: 100%;
    height: auto;
  }
}

/* pagination */
@media print {
  body {

    width: 100%;
  }
  p {
    orphans: 3;
    widows: 3;
  }
  #n-copyright-notice {
    border-bottom: none;
  }
  #toc, #n-introduction {
    page-break-before: always;
  }
  #toc {
    border-top: none;
    padding-top: 0;
  }
  figure, pre {
    page-break-inside: avoid;
  }
  figure {
    overflow: scroll;
  }
  pre.breakable {
    break-inside: auto;
  }
  h1, h2, h3, h4, h5, h6 {
    page-break-after: avoid;
  }
  h2+*, h3+*, h4+*, h5+*, h6+* {
    page-break-before: avoid;
  }
  pre {
    white-space: pre-wrap;
    word-wrap: break-word;
    font-size: 10pt;
  }
  table {
    border: 1px solid #ddd;
  }
  td {
    border-top: 1px solid #ddd;
  }
}

/* This is commented out here, as the string-set: doesn't
   pass W3C validation currently */
/*
.ears thead .left {
  string-set: ears-top-left content();
}

.ears thead .center {
  string-set: ears-top-center content();
}

.ears thead .right {
  string-set: ears-top-right content();
}

.ears tfoot .left {
  string-set: ears-bottom-left content();
}

.ears tfoot .center {
  string-set: ears-bottom-center content();
}

.ears tfoot .right {
  string-set: ears-bottom-right content();
}
*/

@page :first {
  padding-top: 0;
  @top-left {
    content: normal;
    border: none;
  }
  @top-center {
    content: normal;
    border: none;
  }
  @top-right {
    content: normal;
    border: none;
  }
}

@page {
  size: A4;
  margin-bottom: 45mm;
  padding-top: 20px;
  /* The follwing is commented out here, but set appropriately by in code, as
     the content depends on the document */
  /*
  @top-left {
    content: 'Internet-Draft';
    vertical-align: bottom;
    border-bottom: solid 1px #ccc;
  }
  @top-left {
    content: string(ears-top-left);
    vertical-align: bottom;
    border-bottom: solid 1px #ccc;
  }
  @top-center {
    content: string(ears-top-center);
    vertical-align: bottom;
    border-bottom: solid 1px #ccc;
  }
  @top-right {
    content: string(ears-top-right);
    vertical-align: bottom;
    border-bottom: solid 1px #ccc;
  }
  @bottom-left {
    content: string(ears-bottom-left);
    vertical-align: top;
    border-top: solid 1px #ccc;
  }
  @bottom-center {
    content: string(ears-bottom-center);
    vertical-align: top;
    border-top: solid 1px #ccc;
  }
  @bottom-right {
      content: '[Page ' counter(page) ']';
      vertical-align: top;
      border-top: solid 1px #ccc;
  }
  */

}

/* Changes introduced to fix issues found during implementation */
/* Make sure links are clickable even if overlapped by following H* */
a {
  z-index: 2;
}
/* Separate body from document info even without intervening H1 */
section {
  clear: both;
}


/* Top align author divs, to avoid names without organization dropping level with org names */
.author {
  vertical-align: top;
}

/* Leave room in document info to show Internet-Draft on one line */
#identifiers dt {
  width: 8em;
}

/* Don't waste quite as much whitespace between label and value in doc info */
#identifiers dd {
  margin-left: 1em;
}

/* Give floating toc a background color (needed when it's a div inside section */
#toc {
  background-color: white;
}

/* Make the collapsed ToC header render white on gray also when it's a link */
@media screen and (max-width: 1023px) {
  #toc h2 a,
  #toc h2 a:link,
  #toc h2 a:focus,
  #toc h2 a:hover,
  #toc a.toplink,
  #toc a.toplink:hover {
    color: white;
    background-color: #444;
    text-decoration: none;
  }
}

/* Give the bottom of the ToC some whitespace */
@media screen and (min-width: 1024px) {
  #toc {
    padding: 0 0 1em 1em;
  }
}

/* Style section numbers with more space between number and title */
.section-number {
  padding-right: 0.5em;
}

/* prevent monospace from becoming overly large */
tt, code, pre, code {
  font-size: 95%;
}

/* Fix the height/width aspect for ascii art*/
pre.sourcecode,
.art-text pre {
  line-height: 1.12;
}


/* Add styling for a link in the ToC that points to the top of the document */
a.toplink {
  float: right;
  margin-right: 0.5em;
}

/* Fix the dl styling to match the RFC 7992 attributes */
dl > dt,
dl.dlParallel > dt {
  float: left;
  margin-right: 1em;
}
dl.dlNewline > dt {
  float: none;
}

/* Provide styling for table cell text alignment */
table td.text-left,
table th.text-left {
  text-align: left;
}
table td.text-center,
table th.text-center {
  text-align: center;
}
table td.text-right,
table th.text-right {
  text-align: right;
}

/* Make the alternative author contact informatio look less like just another
   author, and group it closer with the primary author contact information */
.alternative-contact {
  margin: 0.5em 0 0.25em 0;
}
address .non-ascii {
  margin: 0 0 0 2em;
}

/* With it being possible to set tables with alignment
  left, center, and right, { width: 100%; } does not make sense */
table {
  width: auto;
}

/* Avoid reference text that sits in a block with very wide left margin,
   because of a long floating dt label.*/
.references dd {
  overflow: visible;
}

/* Control caption placement */
caption {
  caption-side: bottom;
}

/* Limit the width of the author address vcard, so names in right-to-left
   script don't end up on the other side of the page. */

address.vcard {
  max-width: 30em;
  margin-right: auto;
}

/* For address alignment dependent on LTR or RTL scripts */
address div.left {
  text-align: left;
}
address div.right {
  text-align: right;
}

/* Provide table alignment support.  We can't use the alignX classes above
   since they do unwanted things with caption and other styling. */
table.right {
 margin-left: auto;
 margin-right: 0;
}
table.center {
 margin-left: auto;
 margin-right: auto;
}
table.left {
 margin-left: 0;
 margin-right: auto;
}

/* Give the table caption label the same styling as the figcaption */
caption a[href] {
  color: #222;
}

@media print {
  .toplink {
    display: none;
  }

  /* avoid overwriting the top border line with the ToC header */
  #toc {
    padding-top: 1px;
  }

  /* Avoid page breaks inside dl and author address entries */
  .vcard {
    page-break-inside: avoid;
  }

}
/* Tweak the bcp14 keyword presentation */
.bcp14 {
  font-variant: small-caps;
  font-weight: bold;
  font-size: 0.9em;
}
/* Tweak the invisible space above H* in order not to overlay links in text above */
 h2 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 31px;
 }
 h3 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 24px;
 }
 h4 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 24px;
 }
/* Float artwork pilcrow to the right */
@media screen {
  .artwork a.pilcrow {
    display: block;
    line-height: 0.7;
    margin-top: 0.15em;
  }
}
/* Make pilcrows on dd visible */
@media screen {
  dd:hover > a.pilcrow {
    visibility: visible;
  }
}
/* Make the placement of figcaption match that of a table's caption
   by removing the figure's added bottom margin */
.alignLeft.art-text,
.alignCenter.art-text,
.alignRight.art-text {
   margin-bottom: 0;
}
.alignLeft,
.alignCenter,
.alignRight {
  margin: 1em 0 0 0;
}
/* In print, the pilcrow won't show on hover, so prevent it from taking up space,
   possibly even requiring a new line */
@media print {
  a.pilcrow {
    display: none;
  }
}
/* Styling for the external metadata */
div#external-metadata {
  background-color: #eee;
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<table class="ears">
<thead><tr>
<td class="left">RFC 9266</td>
<td class="center">Channel Bindings for TLS 1.3</td>
<td class="right">July 2022</td>
</tr></thead>
<tfoot><tr>
<td class="left">Whited</td>
<td class="center">Standards Track</td>
<td class="right">[Page]</td>
</tr></tfoot>
</table>
<div id="external-metadata" class="document-information"></div>
<div id="internal-metadata" class="document-information">
<dl id="identifiers">
<dt class="label-stream">Stream:</dt>
<dd class="stream">Internet Engineering Task Force (IETF)</dd>
<dt class="label-rfc">RFC:</dt>
<dd class="rfc"><a href="https://www.rfc-editor.org/rfc/rfc9266" class="eref">9266</a></dd>
<dt class="label-updates">Updates:</dt>
<dd class="updates">
<a href="https://www.rfc-editor.org/rfc/rfc5801" class="eref">5801</a>, <a href="https://www.rfc-editor.org/rfc/rfc5802" class="eref">5802</a>, <a href="https://www.rfc-editor.org/rfc/rfc5929" class="eref">5929</a>, <a href="https://www.rfc-editor.org/rfc/rfc7677" class="eref">7677</a> </dd>
<dt class="label-category">Category:</dt>
<dd class="category">Standards Track</dd>
<dt class="label-published">Published:</dt>
<dd class="published">
<time datetime="2022-07" class="published">July 2022</time>
    </dd>
<dt class="label-issn">ISSN:</dt>
<dd class="issn">2070-1721</dd>
<dt class="label-authors">Author:</dt>
<dd class="authors">
<div class="author">
      <div class="author-name">S. Whited</div>
</div>
</dd>
</dl>
</div>
<h1 id="rfcnum">RFC 9266</h1>
<h1 id="title">Channel Bindings for TLS 1.3</h1>
<section id="section-abstract">
      <h2 id="abstract"><a href="#abstract" class="selfRef">Abstract</a></h2>
<p id="section-abstract-1">
        This document defines a channel binding type, tls-exporter, that is
        compatible with TLS 1.3 in accordance with RFC 5056, "On the Use of
        Channel Bindings to Secure Channels".  Furthermore, it updates the
        default channel binding to the new binding for versions of TLS greater
        than 1.2.  This document updates RFCs 5801, 5802, 5929, and 7677.<a href="#section-abstract-1" class="pilcrow">¶</a></p>
</section>
<div id="status-of-memo">
<section id="section-boilerplate.1">
        <h2 id="name-status-of-this-memo">
<a href="#name-status-of-this-memo" class="section-name selfRef">Status of This Memo</a>
        </h2>
<p id="section-boilerplate.1-1">
            This is an Internet Standards Track document.<a href="#section-boilerplate.1-1" class="pilcrow">¶</a></p>
<p id="section-boilerplate.1-2">
            This document is a product of the Internet Engineering Task Force
            (IETF).  It represents the consensus of the IETF community.  It has
            received public review and has been approved for publication by
            the Internet Engineering Steering Group (IESG).  Further
            information on Internet Standards is available in Section 2 of 
            RFC 7841.<a href="#section-boilerplate.1-2" class="pilcrow">¶</a></p>
<p id="section-boilerplate.1-3">
            Information about the current status of this document, any
            errata, and how to provide feedback on it may be obtained at
            <span><a href="https://www.rfc-editor.org/info/rfc9266">https://www.rfc-editor.org/info/rfc9266</a></span>.<a href="#section-boilerplate.1-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="copyright">
<section id="section-boilerplate.2">
        <h2 id="name-copyright-notice">
<a href="#name-copyright-notice" class="section-name selfRef">Copyright Notice</a>
        </h2>
<p id="section-boilerplate.2-1">
            Copyright (c) 2022 IETF Trust and the persons identified as the
            document authors. All rights reserved.<a href="#section-boilerplate.2-1" class="pilcrow">¶</a></p>
<p id="section-boilerplate.2-2">
            This document is subject to BCP 78 and the IETF Trust's Legal
            Provisions Relating to IETF Documents
            (<span><a href="https://trustee.ietf.org/license-info">https://trustee.ietf.org/license-info</a></span>) in effect on the date of
            publication of this document. Please review these documents
            carefully, as they describe your rights and restrictions with
            respect to this document. Code Components extracted from this
            document must include Revised BSD License text as described in
            Section 4.e of the Trust Legal Provisions and are provided without
            warranty as described in the Revised BSD License.<a href="#section-boilerplate.2-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="toc">
<section id="section-toc.1">
        <a href="#" onclick="scroll(0,0)" class="toplink">▲</a><h2 id="name-table-of-contents">
<a href="#name-table-of-contents" class="section-name selfRef">Table of Contents</a>
        </h2>
<nav class="toc"><ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.1">
            <p id="section-toc.1-1.1.1" class="keepWithNext"><a href="#section-1" class="xref">1</a>.  <a href="#name-introduction" class="xref">Introduction</a></p>
<ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.1.2.1">
                <p id="section-toc.1-1.1.2.1.1" class="keepWithNext"><a href="#section-1.1" class="xref">1.1</a>.  <a href="#name-conventions-and-terminology" class="xref">Conventions and Terminology</a></p>
</li>
            </ul>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.2">
            <p id="section-toc.1-1.2.1" class="keepWithNext"><a href="#section-2" class="xref">2</a>.  <a href="#name-the-tls-exporter-channel-bi" class="xref">The 'tls-exporter' Channel Binding Type</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.3">
            <p id="section-toc.1-1.3.1"><a href="#section-3" class="xref">3</a>.  <a href="#name-tls-13-with-scram-or-gss-ap" class="xref">TLS 1.3 with SCRAM or GSS-API over SASL</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.4">
            <p id="section-toc.1-1.4.1"><a href="#section-4" class="xref">4</a>.  <a href="#name-security-considerations" class="xref">Security Considerations</a></p>
<ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.4.2.1">
                <p id="section-toc.1-1.4.2.1.1"><a href="#section-4.1" class="xref">4.1</a>.  <a href="#name-uniqueness-of-channel-bindi" class="xref">Uniqueness of Channel Bindings</a></p>
</li>
              <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.4.2.2">
                <p id="section-toc.1-1.4.2.2.1"><a href="#section-4.2" class="xref">4.2</a>.  <a href="#name-use-with-legacy-tls" class="xref">Use with Legacy TLS</a></p>
</li>
            </ul>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.5">
            <p id="section-toc.1-1.5.1"><a href="#section-5" class="xref">5</a>.  <a href="#name-iana-considerations" class="xref">IANA Considerations</a></p>
<ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.5.2.1">
                <p id="section-toc.1-1.5.2.1.1"><a href="#section-5.1" class="xref">5.1</a>.  <a href="#name-registration-of-channel-bin" class="xref">Registration of Channel Binding Type</a></p>
</li>
              <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.5.2.2">
                <p id="section-toc.1-1.5.2.2.1"><a href="#section-5.2" class="xref">5.2</a>.  <a href="#name-registration-of-channel-bind" class="xref">Registration of Channel Binding TLS Exporter Label</a></p>
</li>
            </ul>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.6">
            <p id="section-toc.1-1.6.1"><a href="#section-6" class="xref">6</a>.  <a href="#name-references" class="xref">References</a></p>
<ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.6.2.1">
                <p id="section-toc.1-1.6.2.1.1"><a href="#section-6.1" class="xref">6.1</a>.  <a href="#name-normative-references" class="xref">Normative References</a></p>
</li>
              <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.6.2.2">
                <p id="section-toc.1-1.6.2.2.1"><a href="#section-6.2" class="xref">6.2</a>.  <a href="#name-informative-references" class="xref">Informative References</a></p>
</li>
            </ul>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.7">
            <p id="section-toc.1-1.7.1"><a href="#appendix-A" class="xref"></a><a href="#name-authors-address" class="xref">Author's Address</a></p>
</li>
        </ul>
</nav>
</section>
</div>
<div id="introduction">
<section id="section-1">
      <h2 id="name-introduction">
<a href="#section-1" class="section-number selfRef">1. </a><a href="#name-introduction" class="section-name selfRef">Introduction</a>
      </h2>
<p id="section-1-1">
        The "tls-unique" channel binding type defined in
        <span>[<a href="#RFC5929" class="xref">RFC5929</a>]</span> was found to be susceptible to the "triple
        handshake vulnerability" <span>[<a href="#TRIPLE-HANDSHAKE" class="xref">TRIPLE-HANDSHAKE</a>]</span> without the
        extended master secret extension defined in <span>[<a href="#RFC7627" class="xref">RFC7627</a>]</span>.
        While TLS 1.3 uses a complete transcript hash akin to the extended
        master secret procedures, the safety of channel bindings with TLS 1.3
        was not analyzed as part of the core protocol work, so the
        specification of channel bindings for TLS 1.3 was deferred.
        <span><a href="https://www.rfc-editor.org/rfc/rfc8446#appendix-C.5" class="relref">Appendix C.5</a> of [<a href="#RFC8446" class="xref">RFC8446</a>]</span> notes the lack of channel bindings
        for TLS 1.3; this document defines such channel bindings and fills that
        gap.
        Furthermore, this document updates <span>[<a href="#RFC5929" class="xref">RFC5929</a>]</span> by adding an
        additional unique channel binding type, "tls-exporter", that replaces
        some usage of "tls-unique".<a href="#section-1-1" class="pilcrow">¶</a></p>
<div id="conventions-and-terminology">
<section id="section-1.1">
        <h3 id="name-conventions-and-terminology">
<a href="#section-1.1" class="section-number selfRef">1.1. </a><a href="#name-conventions-and-terminology" class="section-name selfRef">Conventions and Terminology</a>
        </h3>
<p id="section-1.1-1">
          Throughout this document, the acronym "EKM" is used to refer to
          "Exported Keying Material" as defined in <span>[<a href="#RFC5705" class="xref">RFC5705</a>]</span>.<a href="#section-1.1-1" class="pilcrow">¶</a></p>
<p id="section-1.1-2">
    The key words "<span class="bcp14">MUST</span>", "<span class="bcp14">MUST NOT</span>", "<span class="bcp14">REQUIRED</span>", "<span class="bcp14">SHALL</span>", "<span class="bcp14">SHALL NOT</span>", "<span class="bcp14">SHOULD</span>", "<span class="bcp14">SHOULD NOT</span>", "<span class="bcp14">RECOMMENDED</span>", "<span class="bcp14">NOT RECOMMENDED</span>",
    "<span class="bcp14">MAY</span>", and "<span class="bcp14">OPTIONAL</span>" in this document are to be interpreted as
    described in BCP 14 <span>[<a href="#RFC2119" class="xref">RFC2119</a>]</span> <span>[<a href="#RFC8174" class="xref">RFC8174</a>]</span>
    when, and only when, they appear in all capitals, as shown here.<a href="#section-1.1-2" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="tls-exporter">
<section id="section-2">
      <h2 id="name-the-tls-exporter-channel-bi">
<a href="#section-2" class="section-number selfRef">2. </a><a href="#name-the-tls-exporter-channel-bi" class="section-name selfRef">The 'tls-exporter' Channel Binding Type</a>
      </h2>
<p id="section-2-1">
        Channel binding mechanisms are not useful until TLS implementations
        expose the required data.  To facilitate this, "tls-exporter" uses
        Exported Keying Material (EKM), which is already widely exposed by TLS
        implementations.  The EKM is obtained using the keying material
        exporters for TLS, as defined in <span>[<a href="#RFC5705" class="xref">RFC5705</a>]</span> and <span><a href="https://www.rfc-editor.org/rfc/rfc8446#section-7.5" class="relref">Section 7.5</a> of [<a href="#RFC8446" class="xref">RFC8446</a>]</span>, by supplying the
        following inputs:<a href="#section-2-1" class="pilcrow">¶</a></p>
<span class="break"></span><dl class="dlParallel" id="section-2-2">
        <dt id="section-2-2.1">Label:</dt>
        <dd style="margin-left: 1.5em" id="section-2-2.2">
          The ASCII string "EXPORTER-Channel-Binding" with no terminating NUL.<a href="#section-2-2.2" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
<dt id="section-2-2.3">Context value:</dt>
        <dd style="margin-left: 1.5em" id="section-2-2.4">
          Zero-length string.<a href="#section-2-2.4" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
<dt id="section-2-2.5">Length:</dt>
        <dd style="margin-left: 1.5em" id="section-2-2.6">
          32 bytes.<a href="#section-2-2.6" class="pilcrow">¶</a>
</dd>
      <dd class="break"></dd>
</dl>
<p id="section-2-3">
        This channel binding mechanism is defined only when the TLS handshake
        results in unique master secrets. This is true of TLS versions prior to
        1.3 when the extended master secret extension of
        <span>[<a href="#RFC7627" class="xref">RFC7627</a>]</span> is in use, and it is always true for TLS 1.3
        (see <span><a href="https://www.rfc-editor.org/rfc/rfc8446#appendix-D" class="relref">Appendix D</a> of [<a href="#RFC8446" class="xref">RFC8446</a>]</span>).<a href="#section-2-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="scram">
<section id="section-3">
      <h2 id="name-tls-13-with-scram-or-gss-ap">
<a href="#section-3" class="section-number selfRef">3. </a><a href="#name-tls-13-with-scram-or-gss-ap" class="section-name selfRef">TLS 1.3 with SCRAM or GSS-API over SASL</a>
      </h2>
<p id="section-3-1">
        The specifications for Salted Challenge Response Authentication Mechanism (SCRAM) <span>[<a href="#RFC5802" class="xref">RFC5802</a>]</span> <span>[<a href="#RFC7677" class="xref">RFC7677</a>]</span> and Generic Security
        Service Application Program Interface (GSS-API) over Simple
        Authentication and Security Layer (SASL) <span>[<a href="#RFC5801" class="xref">RFC5801</a>]</span>
        define "tls-unique" as the default channel binding to use over TLS.
        As "tls-unique" is not defined for TLS 1.3 (and greater), this
        document updates <span>[<a href="#RFC5801" class="xref">RFC5801</a>]</span>, <span>[<a href="#RFC5802" class="xref">RFC5802</a>]</span>,
        and <span>[<a href="#RFC7677" class="xref">RFC7677</a>]</span> to use "tls-exporter" as the default
        channel binding over TLS 1.3 (and greater).
        Note that this document does not change the default channel
        binding for SCRAM mechanisms over TLS 1.2 <span>[<a href="#RFC5246" class="xref">RFC5246</a>]</span>,
        which is still "tls-unique" (also note that RFC 5246 has been obsoleted
        by RFC 8446).<a href="#section-3-1" class="pilcrow">¶</a></p>
<p id="section-3-2">
        Additionally, this document updates the aforementioned documents to make
        "tls-exporter" the mandatory-to-implement channel binding if any channel
        bindings are implemented for TLS 1.3.
        Implementations that support channel binding over TLS 1.3
        <span class="bcp14">MUST</span> implement "tls-exporter".<a href="#section-3-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="security-considerations">
<section id="section-4">
      <h2 id="name-security-considerations">
<a href="#section-4" class="section-number selfRef">4. </a><a href="#name-security-considerations" class="section-name selfRef">Security Considerations</a>
      </h2>
<p id="section-4-1">
        The channel binding type defined in this document is constructed so that
        disclosure of the channel binding data does not leak secret information
        about the TLS channel and does not affect the security of the TLS
        channel.<a href="#section-4-1" class="pilcrow">¶</a></p>
<p id="section-4-2">
        The derived data <span class="bcp14">MUST NOT</span> be used for any purpose other
        than channel bindings as described in <span>[<a href="#RFC5056" class="xref">RFC5056</a>]</span>.
        In particular, implementations <span class="bcp14">MUST NOT</span> use channel binding as a
        secret key to protect privileged information.<a href="#section-4-2" class="pilcrow">¶</a></p>
<p id="section-4-3">
        The Security Considerations sections of <span>[<a href="#RFC5056" class="xref">RFC5056</a>]</span>, <span>[<a href="#RFC5705" class="xref">RFC5705</a>]</span>, and <span>[<a href="#RFC8446" class="xref">RFC8446</a>]</span> apply to this document.<a href="#section-4-3" class="pilcrow">¶</a></p>
<div id="unique-bindings">
<section id="section-4.1">
        <h3 id="name-uniqueness-of-channel-bindi">
<a href="#section-4.1" class="section-number selfRef">4.1. </a><a href="#name-uniqueness-of-channel-bindi" class="section-name selfRef">Uniqueness of Channel Bindings</a>
        </h3>
<p id="section-4.1-1">
          The definition of channel bindings in <span>[<a href="#RFC5056" class="xref">RFC5056</a>]</span>
          defines the concept of a "unique" channel binding as being one that
          is unique to the channel endpoints and unique over time, that is,
          a value that is unique to a specific instance of the lower-layer
          security protocol.
          When TLS is the lower-layer security protocol, as for the channel binding
          type defined in this document, this concept of uniqueness
          corresponds to uniquely identifying the specific TLS connection.<a href="#section-4.1-1" class="pilcrow">¶</a></p>
<p id="section-4.1-2">
          However, a stronger form of uniqueness is possible, which would entail
          uniquely identifying not just the lower-layer protocol but also the
          upper-layer application or authentication protocol that is consuming
          the channel binding.
          The distinction is relevant only when there are multiple instances of
          an authentication protocol, or multiple distinct authentication
          protocols, that run atop the same lower-layer protocol.
          Such a situation is rare; most consumers of channel bindings
          establish an instance of the lower-layer secure protocol, run a single
          application or authentication protocol as the upper-layer protocol,
          then terminate both upper and lower-layer protocols.
          In this situation, the stronger form of uniqueness is trivially
          achieved, given that the channel binding value is unique in the sense
          of <span>[<a href="#RFC5056" class="xref">RFC5056</a>]</span>.<a href="#section-4.1-2" class="pilcrow">¶</a></p>
<p id="section-4.1-3">
          The channel binding type defined by this document provides only the
          weaker type of uniqueness, as per <span>[<a href="#RFC5056" class="xref">RFC5056</a>]</span>; it does
          not achieve the stronger uniqueness per the upper-layer protocol
          instance described above.  This stronger form of uniqueness would be
          useful in that it provides protection against cross-protocol attacks
          for the multiple authentication protocols running over the same
          instance of the lower-layer protocol, and it provides protection
          against replay attacks that seek to replay a message from one
          instance of an authentication protocol in a different instance of
          the same authentication protocol, again running over the same
          instance of the lower-layer protocol.  Both of these properties are
          highly desirable when performing formal analysis of upper-layer
          protocols; if these properties are not provided, such formal
          analysis is essentially impossible.  In some cases, one or both of
          these properties may already be provided by specific upper-layer
          protocols, but that is dependent on the mechanism(s) in question,
          and formal analysis requires that the property is provided in a
          generic manner across all potential upper-layer protocols that
          exist or might exist in the future.<a href="#section-4.1-3" class="pilcrow">¶</a></p>
<p id="section-4.1-4">
          Accordingly, applications that make use of the channel binding type
          defined in this document <span class="bcp14">MUST NOT</span> use the channel
          binding for more than one authentication mechanism instance on a given
          TLS connection.
          Such applications <span class="bcp14">MUST</span> immediately close the TLS
          connection after the conclusion of the upper-layer protocol.<a href="#section-4.1-4" class="pilcrow">¶</a></p>
</section>
</div>
<div id="legacy-tls">
<section id="section-4.2">
        <h3 id="name-use-with-legacy-tls">
<a href="#section-4.2" class="section-number selfRef">4.2. </a><a href="#name-use-with-legacy-tls" class="section-name selfRef">Use with Legacy TLS</a>
        </h3>
<p id="section-4.2-1">
          While it is possible to use this channel binding mechanism with TLS
          versions below 1.3, extra precaution must be taken to ensure that
          the chosen cipher suites always result in unique master secrets.
          For more information, see <span>[<a href="#RFC7627" class="xref">RFC7627</a>]</span> and the Security
          Considerations section of <span>[<a href="#RFC5705" class="xref">RFC5705</a>]</span> (TLS 1.3 always
          provides unique master secrets, as discussed in <span><a href="https://www.rfc-editor.org/rfc/rfc8446#appendix-D" class="relref">Appendix D</a> of [<a href="#RFC8446" class="xref">RFC8446</a>]</span>).<a href="#section-4.2-1" class="pilcrow">¶</a></p>
<p id="section-4.2-2">
          When TLS renegotiation is enabled on a connection, the "tls-exporter"
          channel binding type is not defined for that connection, and
          implementations <span class="bcp14">MUST NOT</span> support it.<a href="#section-4.2-2" class="pilcrow">¶</a></p>
<p id="section-4.2-3">
          In general, users wishing to take advantage of channel binding should
          upgrade to TLS 1.3 or later.<a href="#section-4.2-3" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="iana-considerations">
<section id="section-5">
      <h2 id="name-iana-considerations">
<a href="#section-5" class="section-number selfRef">5. </a><a href="#name-iana-considerations" class="section-name selfRef">IANA Considerations</a>
      </h2>
<div id="cb-type-registration">
<section id="section-5.1">
        <h3 id="name-registration-of-channel-bin">
<a href="#section-5.1" class="section-number selfRef">5.1. </a><a href="#name-registration-of-channel-bin" class="section-name selfRef">Registration of Channel Binding Type</a>
        </h3>
<p id="section-5.1-1">
          IANA has registered tls-exporter in the "Channel-Binding
          Types" registry:<a href="#section-5.1-1" class="pilcrow">¶</a></p>
<span class="break"></span><dl class="dlParallel" id="section-5.1-2">
          <dt id="section-5.1-2.1">Channel-binding unique prefix:</dt>
          <dd style="margin-left: 1.5em" id="section-5.1-2.2">tls-exporter<a href="#section-5.1-2.2" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-5.1-2.3">Channel-binding type:</dt>
          <dd style="margin-left: 1.5em" id="section-5.1-2.4">unique<a href="#section-5.1-2.4" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-5.1-2.5">Channel type:</dt>
          <dd style="margin-left: 1.5em" id="section-5.1-2.6">TLS <span>[<a href="#RFC8446" class="xref">RFC8446</a>]</span><a href="#section-5.1-2.6" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-5.1-2.7">Published specification:</dt>
          <dd style="margin-left: 1.5em" id="section-5.1-2.8">RFC 9266<a href="#section-5.1-2.8" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-5.1-2.9">Channel-binding is secret:</dt>
          <dd style="margin-left: 1.5em" id="section-5.1-2.10">no<a href="#section-5.1-2.10" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-5.1-2.11">Description:</dt>
          <dd style="margin-left: 1.5em" id="section-5.1-2.12">The EKM value obtained from the current TLS connection.<a href="#section-5.1-2.12" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-5.1-2.13">Intended usage:</dt>
          <dd style="margin-left: 1.5em" id="section-5.1-2.14">COMMON<a href="#section-5.1-2.14" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-5.1-2.15">
            Person and email address to contact for further information:
          </dt>
          <dd style="margin-left: 1.5em" id="section-5.1-2.16">Sam Whited &lt;sam@samwhited.com&gt;<a href="#section-5.1-2.16" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-5.1-2.17">Owner/Change controller name and email address:</dt>
          <dd style="margin-left: 1.5em" id="section-5.1-2.18">IESG<a href="#section-5.1-2.18" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-5.1-2.19">Expert reviewer name and contact information:</dt>
          <dd style="margin-left: 1.5em" id="section-5.1-2.20">
            IETF KITTEN WG &lt;kitten@ietf.org&gt; or IETF TLS WG &lt;tls@ietf.org&gt;<a href="#section-5.1-2.20" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-5.1-2.21">Note:</dt>
          <dd style="margin-left: 1.5em" id="section-5.1-2.22">
            See the published specification for advice on the applicability of
            this channel binding type.<a href="#section-5.1-2.22" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
</dl>
</section>
</div>
<div id="exporter-registration">
<section id="section-5.2">
        <h3 id="name-registration-of-channel-bind">
<a href="#section-5.2" class="section-number selfRef">5.2. </a><a href="#name-registration-of-channel-bind" class="section-name selfRef">Registration of Channel Binding TLS Exporter Label</a>
        </h3>
<p id="section-5.2-1">
          IANA has added the following registration in the "TLS Exporter
          Labels" registry under the "Transport Layer Security (TLS)
          Parameters" registry:<a href="#section-5.2-1" class="pilcrow">¶</a></p>
<span class="break"></span><dl class="dlParallel" id="section-5.2-2">
          <dt id="section-5.2-2.1">Value:</dt>
          <dd style="margin-left: 1.5em" id="section-5.2-2.2">EXPORTER-Channel-Binding<a href="#section-5.2-2.2" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-5.2-2.3">DTLS-OK:</dt>
          <dd style="margin-left: 1.5em" id="section-5.2-2.4">Y<a href="#section-5.2-2.4" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-5.2-2.5">Recommended:</dt>
          <dd style="margin-left: 1.5em" id="section-5.2-2.6">Y<a href="#section-5.2-2.6" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-5.2-2.7">Reference:</dt>
          <dd style="margin-left: 1.5em" id="section-5.2-2.8">RFC 9266<a href="#section-5.2-2.8" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
</dl>
</section>
</div>
</section>
</div>
<section id="section-6">
      <h2 id="name-references">
<a href="#section-6" class="section-number selfRef">6. </a><a href="#name-references" class="section-name selfRef">References</a>
      </h2>
<section id="section-6.1">
        <h3 id="name-normative-references">
<a href="#section-6.1" class="section-number selfRef">6.1. </a><a href="#name-normative-references" class="section-name selfRef">Normative References</a>
        </h3>
<dl class="references">
<dt id="RFC2119">[RFC2119]</dt>
        <dd>
<span class="refAuthor">Bradner, S.</span>, <span class="refTitle">"Key words for use in RFCs to Indicate Requirement Levels"</span>, <span class="seriesInfo">BCP 14</span>, <span class="seriesInfo">RFC 2119</span>, <span class="seriesInfo">DOI 10.17487/RFC2119</span>, <time datetime="1997-03" class="refDate">March 1997</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc2119">https://www.rfc-editor.org/info/rfc2119</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC5056">[RFC5056]</dt>
        <dd>
<span class="refAuthor">Williams, N.</span>, <span class="refTitle">"On the Use of Channel Bindings to Secure Channels"</span>, <span class="seriesInfo">RFC 5056</span>, <span class="seriesInfo">DOI 10.17487/RFC5056</span>, <time datetime="2007-11" class="refDate">November 2007</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc5056">https://www.rfc-editor.org/info/rfc5056</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC5705">[RFC5705]</dt>
        <dd>
<span class="refAuthor">Rescorla, E.</span>, <span class="refTitle">"Keying Material Exporters for Transport Layer Security (TLS)"</span>, <span class="seriesInfo">RFC 5705</span>, <span class="seriesInfo">DOI 10.17487/RFC5705</span>, <time datetime="2010-03" class="refDate">March 2010</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc5705">https://www.rfc-editor.org/info/rfc5705</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC5801">[RFC5801]</dt>
        <dd>
<span class="refAuthor">Josefsson, S.</span> and <span class="refAuthor">N. Williams</span>, <span class="refTitle">"Using Generic Security Service Application Program Interface (GSS-API) Mechanisms in Simple Authentication and Security Layer (SASL): The GS2 Mechanism Family"</span>, <span class="seriesInfo">RFC 5801</span>, <span class="seriesInfo">DOI 10.17487/RFC5801</span>, <time datetime="2010-07" class="refDate">July 2010</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc5801">https://www.rfc-editor.org/info/rfc5801</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC5802">[RFC5802]</dt>
        <dd>
<span class="refAuthor">Newman, C.</span>, <span class="refAuthor">Menon-Sen, A.</span>, <span class="refAuthor">Melnikov, A.</span>, and <span class="refAuthor">N. Williams</span>, <span class="refTitle">"Salted Challenge Response Authentication Mechanism (SCRAM) SASL and GSS-API Mechanisms"</span>, <span class="seriesInfo">RFC 5802</span>, <span class="seriesInfo">DOI 10.17487/RFC5802</span>, <time datetime="2010-07" class="refDate">July 2010</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc5802">https://www.rfc-editor.org/info/rfc5802</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC5929">[RFC5929]</dt>
        <dd>
<span class="refAuthor">Altman, J.</span>, <span class="refAuthor">Williams, N.</span>, and <span class="refAuthor">L. Zhu</span>, <span class="refTitle">"Channel Bindings for TLS"</span>, <span class="seriesInfo">RFC 5929</span>, <span class="seriesInfo">DOI 10.17487/RFC5929</span>, <time datetime="2010-07" class="refDate">July 2010</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc5929">https://www.rfc-editor.org/info/rfc5929</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC7677">[RFC7677]</dt>
        <dd>
<span class="refAuthor">Hansen, T.</span>, <span class="refTitle">"SCRAM-SHA-256 and SCRAM-SHA-256-PLUS Simple Authentication and Security Layer (SASL) Mechanisms"</span>, <span class="seriesInfo">RFC 7677</span>, <span class="seriesInfo">DOI 10.17487/RFC7677</span>, <time datetime="2015-11" class="refDate">November 2015</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7677">https://www.rfc-editor.org/info/rfc7677</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8174">[RFC8174]</dt>
        <dd>
<span class="refAuthor">Leiba, B.</span>, <span class="refTitle">"Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words"</span>, <span class="seriesInfo">BCP 14</span>, <span class="seriesInfo">RFC 8174</span>, <span class="seriesInfo">DOI 10.17487/RFC8174</span>, <time datetime="2017-05" class="refDate">May 2017</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8174">https://www.rfc-editor.org/info/rfc8174</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8446">[RFC8446]</dt>
      <dd>
<span class="refAuthor">Rescorla, E.</span>, <span class="refTitle">"The Transport Layer Security (TLS) Protocol Version 1.3"</span>, <span class="seriesInfo">RFC 8446</span>, <span class="seriesInfo">DOI 10.17487/RFC8446</span>, <time datetime="2018-08" class="refDate">August 2018</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8446">https://www.rfc-editor.org/info/rfc8446</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
<section id="section-6.2">
        <h3 id="name-informative-references">
<a href="#section-6.2" class="section-number selfRef">6.2. </a><a href="#name-informative-references" class="section-name selfRef">Informative References</a>
        </h3>
<dl class="references">
<dt id="RFC5246">[RFC5246]</dt>
        <dd>
<span class="refAuthor">Dierks, T.</span> and <span class="refAuthor">E. Rescorla</span>, <span class="refTitle">"The Transport Layer Security (TLS) Protocol Version 1.2"</span>, <span class="seriesInfo">RFC 5246</span>, <span class="seriesInfo">DOI 10.17487/RFC5246</span>, <time datetime="2008-08" class="refDate">August 2008</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc5246">https://www.rfc-editor.org/info/rfc5246</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC7627">[RFC7627]</dt>
        <dd>
<span class="refAuthor">Bhargavan, K., Ed.</span>, <span class="refAuthor">Delignat-Lavaud, A.</span>, <span class="refAuthor">Pironti, A.</span>, <span class="refAuthor">Langley, A.</span>, and <span class="refAuthor">M. Ray</span>, <span class="refTitle">"Transport Layer Security (TLS) Session Hash and Extended Master Secret Extension"</span>, <span class="seriesInfo">RFC 7627</span>, <span class="seriesInfo">DOI 10.17487/RFC7627</span>, <time datetime="2015-09" class="refDate">September 2015</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7627">https://www.rfc-editor.org/info/rfc7627</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="TRIPLE-HANDSHAKE">[TRIPLE-HANDSHAKE]</dt>
      <dd>
<span class="refAuthor">Bhargavan, K.</span>, <span class="refAuthor">Delignat-Lavaud, A.</span>, <span class="refAuthor">Fournet, C.</span>, <span class="refAuthor">Pironti, A.</span>, and <span class="refAuthor">P. Strub</span>, <span class="refTitle">"Triple Handshakes Considered Harmful: Breaking and Fixing Authentication over TLS"</span>, <time datetime="2014-03" class="refDate">March 2014</time>, <span>&lt;<a href="https://www.mitls.org/pages/attacks/3SHAKE">https://www.mitls.org/pages/attacks/3SHAKE</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
</section>
<div id="authors-addresses">
<section id="appendix-A">
      <h2 id="name-authors-address">
<a href="#name-authors-address" class="section-name selfRef">Author's Address</a>
      </h2>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Sam Whited</span></div>
<div dir="auto" class="left">
<span class="locality">Atlanta</span>, <span class="region">GA</span> </div>
<div dir="auto" class="left"><span class="country-name">United States of America</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:sam@samwhited.com" class="email">sam@samwhited.com</a>
</div>
<div class="url">
<span>URI:</span>
<a href="https://blog.samwhited.com/" class="url">https://blog.samwhited.com/</a>
</div>
</address>
</section>
</div>
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