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<title>OpenID Connect Key Binding 1.0 - draft 00</title>
<meta content="Dick Hardt" name="author">
<meta content="Ethan Heilman" name="author">
<meta content="
OpenID Key Binding specifies how to bind a public key to an OpenID Connect ID Token using mechanisms defined in , OAuth 2.0 Demonstrating Proof of Possession (DPoP).
" name="description">
<meta content="xml2rfc 3.30.2" name="generator">
<meta content="security" name="keyword">
<meta content="openid" name="keyword">
<meta content="lifecycle" name="keyword">
<meta content="openid-key-binding-1_0" name="ietf.draft">
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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,
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/* Make the placement of figcaption match that of a table's caption
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<body class="xml2rfc">
<table class="ears">
<thead><tr>
<td class="left"></td>
<td class="center">openid-connect-key-binding</td>
<td class="right">October 2025</td>
</tr></thead>
<tfoot><tr>
<td class="left">Hardt & Heilman</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-workgroup">Workgroup:</dt>
<dd class="workgroup">OpenID Connect</dd>
<dt class="label-published">Published:</dt>
<dd class="published">
<time datetime="2025-10-03" class="published">3 October 2025</time>
</dd>
<dt class="label-authors">Authors:</dt>
<dd class="authors">
<div class="author">
<div class="author-name">D. Hardt</div>
<div class="org">Hellō</div>
</div>
<div class="author">
<div class="author-name">E. Heilman</div>
<div class="org">Cloudflare</div>
</div>
</dd>
</dl>
</div>
<h1 id="title">OpenID Connect Key Binding 1.0 - draft 00</h1>
<section id="section-abstract">
<h2 id="abstract"><a href="#abstract" class="selfRef">Abstract</a></h2>
<p id="section-abstract-1">OpenID Key Binding specifies how to bind a public key to an OpenID Connect ID Token using mechanisms defined in <span>[<a href="#RFC9449" class="cite xref">RFC9449</a>]</span>, OAuth 2.0 Demonstrating Proof of Possession (DPoP).<a href="#section-abstract-1" class="pilcrow">¶</a></p>
</section>
<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"><a href="#section-1" class="auto internal xref">1</a>. <a href="#name-introduction" class="internal 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="auto internal xref">1.1</a>. <a href="#name-requirements-notation-and-c" class="internal xref">Requirements Notation and Conventions</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.1.2.2">
<p id="section-toc.1-1.1.2.2.1" class="keepWithNext"><a href="#section-1.2" class="auto internal xref">1.2</a>. <a href="#name-terminology" class="internal xref">Terminology</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.1.2.3">
<p id="section-toc.1-1.1.2.3.1" class="keepWithNext"><a href="#section-1.3" class="auto internal xref">1.3</a>. <a href="#name-protocol-profile-overview" class="internal xref">Protocol Profile Overview</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.1.2.4">
<p id="section-toc.1-1.1.2.4.1"><a href="#section-1.4" class="auto internal xref">1.4</a>. <a href="#name-openid-connect-metadata" class="internal xref">OpenID Connect Metadata</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.1.2.5">
<p id="section-toc.1-1.1.2.5.1"><a href="#section-1.5" class="auto internal xref">1.5</a>. <a href="#name-authentication-request-auth" class="internal xref">Authentication Request - Authorization Code Flow</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.1.2.6">
<p id="section-toc.1-1.1.2.6.1"><a href="#section-1.6" class="auto internal xref">1.6</a>. <a href="#name-authentication-request-devi" class="internal xref">Authentication Request - Device Authorization Flow</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.1.2.7">
<p id="section-toc.1-1.1.2.7.1"><a href="#section-1.7" class="auto internal xref">1.7</a>. <a href="#name-authentication-response" class="internal xref">Authentication Response</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.1.2.8">
<p id="section-toc.1-1.1.2.8.1"><a href="#section-1.8" class="auto internal xref">1.8</a>. <a href="#name-token-request" class="internal xref">Token Request</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.1.2.9">
<p id="section-toc.1-1.1.2.9.1"><a href="#section-1.9" class="auto internal xref">1.9</a>. <a href="#name-token-response" class="internal xref">Token Response</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.1.2.10">
<p id="section-toc.1-1.1.2.10.1"><a href="#section-1.10" class="auto internal xref">1.10</a>. <a href="#name-id-token-proof-of-possessio" class="internal xref">ID Token Proof of Possession</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"><a href="#section-2" class="auto internal xref">2</a>. <a href="#name-privacy-considerations" class="internal xref">Privacy Considerations</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="auto internal xref">3</a>. <a href="#name-security-considerations" class="internal xref">Security Considerations</a></p>
<ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.3.2.1">
<p id="section-toc.1-1.3.2.1.1"><a href="#section-3.1" class="auto internal xref">3.1</a>. <a href="#name-require-proof-of-possesion" class="internal xref">Require Proof of Possesion</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.3.2.2">
<p id="section-toc.1-1.3.2.2.1"><a href="#section-3.2" class="auto internal xref">3.2</a>. <a href="#name-id-token-reverification" class="internal xref">ID Token Reverification</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.3.2.3">
<p id="section-toc.1-1.3.2.3.1"><a href="#section-3.3" class="auto internal xref">3.3</a>. <a href="#name-use-as-access-token" class="internal xref">Use as Access Token</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.3.2.4">
<p id="section-toc.1-1.3.2.4.1"><a href="#section-3.4" class="auto internal xref">3.4</a>. <a href="#name-unique-key-pair" class="internal xref">Unique Key Pair</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.3.2.5">
<p id="section-toc.1-1.3.2.5.1"><a href="#section-3.5" class="auto internal xref">3.5</a>. <a href="#name-using-cnf-as-a-user-claim" class="internal xref">Using cnf as a User Claim</a></p>
</li>
</ul>
</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="auto internal xref">4</a>. <a href="#name-iana-considerations" class="internal xref">IANA Considerations</a></p>
</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="auto internal xref">5</a>. <a href="#name-references" class="internal xref">References</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="auto internal xref">5.1</a>. <a href="#name-normative-references" class="internal xref">Normative References</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="auto internal xref">5.2</a>. <a href="#name-informative-references" class="internal xref">Informative References</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="#appendix-A" class="auto internal xref">Appendix A</a>. <a href="#name-acknowledgements" class="internal xref">Acknowledgements</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.7">
<p id="section-toc.1-1.7.1"><a href="#appendix-B" class="auto internal xref">Appendix B</a>. <a href="#name-notices" class="internal xref">Notices</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.8">
<p id="section-toc.1-1.8.1"><a href="#appendix-C" class="auto internal xref">Appendix C</a>. <a href="#name-document-history" class="internal xref">Document History</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.9">
<p id="section-toc.1-1.9.1"><a href="#appendix-D" class="auto internal xref"></a><a href="#name-authors-addresses" class="internal xref">Authors' Addresses</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">OpenID Connect is a protocol that enables a Relying Party (RP) to delegate authentication and obtain identity claims to an OpenID Connect Provider (OP).<a href="#section-1-1" class="pilcrow">¶</a></p>
<p id="section-1-2">When authenticating with OpenID Connect, an RP provides a nonce in its authentication request. The ID Token signed and returned by the OP contains the nonce and claims about the user. When verifying the ID Token, the RP confirms it contains the nonce, binding the session that made the request to the response.<a href="#section-1-2" class="pilcrow">¶</a></p>
<p id="section-1-3">It is common for an RP to be composed of multiple components such as a RP authenticating component that obtains the ID Token from the OP and an RP consuming component which checks the ID Token presented to it by the authenticating component. When the RP authenticating component wants to prove to an RP consuming component that it has authenticated a user, it may present the ID Token as a bearer token. However, bearer tokens are vulnerable to theft and replay attacks - if an attacker obtains the ID Token, they can impersonate the authenticated user.<a href="#section-1-3" class="pilcrow">¶</a></p>
<p id="section-1-4">By binding a cryptographic key to the ID Token, the RP authenticating component can prove to RP consuming components not only that a user has been authenticated, but that the RP authenticating component itself was the original recipient of that authentication. This transforms the ID Token from a vulnerable bearer token into a proof-of-possession token that provides stronger security guarantees.<a href="#section-1-4" class="pilcrow">¶</a></p>
<p id="section-1-5">The RP may also prove possession of the bound key when presenting an ID Token back to the OP.<a href="#section-1-5" class="pilcrow">¶</a></p>
<p id="section-1-6">Use cases include: a mobile app that has received an ID Token exchanging the ID Token with a proof of possession with a first party authorization service for an access token; an instance of a peer to peer application such as video conferencing where one instance of the application sends the ID Token with a proof of possession to a second instance to prove which user is operating the first instance.<a href="#section-1-6" class="pilcrow">¶</a></p>
<p id="section-1-7">This specification profiles OpenID Connect 1.0 <span>[<a href="#OpenID.Core" class="cite xref">OpenID.Core</a>]</span>, RFC8628 - OAuth 2.0 Device Authorization Grant <span>[<a href="#RFC8626" class="cite xref">RFC8626</a>]</span>, and RFC9449 - OAuth 2.0 Demonstrating Proof of Possession (DPoP) <span>[<a href="#RFC9449" class="cite xref">RFC9449</a>]</span> to enable cryptographically bound ID Tokens that resist theft and replay attacks while maintaining compatibility with existing OpenID Connect infrastructure.<a href="#section-1-7" class="pilcrow">¶</a></p>
<div id="requirements-notation-and-conventions">
<section id="section-1.1">
<h3 id="name-requirements-notation-and-c">
<a href="#section-1.1" class="section-number selfRef">1.1. </a><a href="#name-requirements-notation-and-c" class="section-name selfRef">Requirements Notation and Conventions</a>
</h3>
<p id="section-1.1-1">The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in <span>[<a href="#RFC2119" class="cite xref">RFC2119</a>]</span>.<a href="#section-1.1-1" class="pilcrow">¶</a></p>
<p id="section-1.1-2">In the .txt version of this specification,
values are quoted to indicate that they are to be taken literally.
When using these values in protocol messages,
the quotes MUST NOT be used as part of the value.
In the HTML version of this specification,
values to be taken literally are indicated by
the use of <em>this fixed-width font</em>.<a href="#section-1.1-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="terminology">
<section id="section-1.2">
<h3 id="name-terminology">
<a href="#section-1.2" class="section-number selfRef">1.2. </a><a href="#name-terminology" class="section-name selfRef">Terminology</a>
</h3>
<p id="section-1.2-1">This specification uses the following terms:<a href="#section-1.2-1" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-1.2-2.1">
<p id="section-1.2-2.1.1"><strong>OP</strong>: The OpenID Provider as defined in <span>[<a href="#OpenID.Core" class="cite xref">OpenID.Core</a>]</span>.<a href="#section-1.2-2.1.1" class="pilcrow">¶</a></p>
</li>
<li class="normal" id="section-1.2-2.2">
<p id="section-1.2-2.2.1"><strong>RP</strong>: The Relying Party as defined in <span>[<a href="#OpenID.Core" class="cite xref">OpenID.Core</a>]</span>.<a href="#section-1.2-2.2.1" class="pilcrow">¶</a></p>
</li>
</ul>
<p id="section-1.2-3">The parameters <strong>dpop_jkt</strong> and <strong>DPoP</strong> as defined in <span>[<a href="#RFC9449" class="cite xref">RFC9449</a>]</span><a href="#section-1.2-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="protocol-profile-overview">
<section id="section-1.3">
<h3 id="name-protocol-profile-overview">
<a href="#section-1.3" class="section-number selfRef">1.3. </a><a href="#name-protocol-profile-overview" class="section-name selfRef">Protocol Profile Overview</a>
</h3>
<p id="section-1.3-1">This specification profiles how to bind a public key to an ID Token by:<a href="#section-1.3-1" class="pilcrow">¶</a></p>
<ol start="1" type="1" class="normal type-1" id="section-1.3-2">
<li id="section-1.3-2.1">
<p id="section-1.3-2.1.1">adding the <code>bound_key</code> scope and <code>dpop_jkt</code> parameter to the OpenID Connect Authentication Request<a href="#section-1.3-2.1.1" class="pilcrow">¶</a></p>
</li>
<li id="section-1.3-2.2">
<p id="section-1.3-2.2.1">receiving the authorization <code>code</code> as usual in the Authentication Response<a href="#section-1.3-2.2.1" class="pilcrow">¶</a></p>
</li>
<li id="section-1.3-2.3">
<p id="section-1.3-2.3.1">adding the <code>DPoP</code> header that includes the hash of the <code>code</code>, <code>c_hash</code>, as a claim in the Token Request to the OP <code>token_endpoint</code><a href="#section-1.3-2.3.1" class="pilcrow">¶</a></p>
</li>
<li id="section-1.3-2.4">
<p id="section-1.3-2.4.1">adding the <code>cnf</code> claim containing the public key to the returned ID Token<a href="#section-1.3-2.4.1" class="pilcrow">¶</a></p>
</li>
</ol>
<div class="alignLeft art-text artwork" id="section-1.3-3">
<pre>+------+ +------+
| |-- Authentication Request --->| |
| RP | (1) bound_key & dpop_jkt | OP |
| | | |
| |<-- Authentication Response --| |
| | (2) authorization code | |
| | | |
| |-- Token Request ------------>| |
| | (3) DPoP header w/ c_hash | |
| | | |
| |<-- Token Response -----------| |
| | (4) cnf claim containing | |
| | the public key in ID Token | |
+------+ +------+
</pre><a href="#section-1.3-3" class="pilcrow">¶</a>
</div>
</section>
</div>
<div id="openid-connect-metadata">
<section id="section-1.4">
<h3 id="name-openid-connect-metadata">
<a href="#section-1.4" class="section-number selfRef">1.4. </a><a href="#name-openid-connect-metadata" class="section-name selfRef">OpenID Connect Metadata</a>
</h3>
<p id="section-1.4-1">The OP's OpenID Connect Metadata Document <span>[<a href="#OpenID.Discovery" class="cite xref">OpenID.Discovery</a>]</span> SHOULD include:<a href="#section-1.4-1" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-1.4-2.1">
<p id="section-1.4-2.1.1">the <code>bound_key</code> scope in the <code>supported_scopes</code><a href="#section-1.4-2.1.1" class="pilcrow">¶</a></p>
</li>
<li class="normal" id="section-1.4-2.2">
<p id="section-1.4-2.2.1">the <code>dpop_signing_alg_values_supported</code> property containing a list of supported algorithms as defined in <span>[<a href="#IANA.JOSE.ALGS" class="cite xref">IANA.JOSE.ALGS</a>]</span><a href="#section-1.4-2.2.1" class="pilcrow">¶</a></p>
</li>
</ul>
</section>
</div>
<div id="authentication-request-authorization-code-flow">
<section id="section-1.5">
<h3 id="name-authentication-request-auth">
<a href="#section-1.5" class="section-number selfRef">1.5. </a><a href="#name-authentication-request-auth" class="section-name selfRef">Authentication Request - Authorization Code Flow</a>
</h3>
<p id="section-1.5-1">If the RP authenticating component is running on a device that supports a web browser, it makes an authorization request per <span>[<a href="#OpenID.Core" class="cite xref">OpenID.Core</a>]</span> 3.1. In addition to the <code>scope</code> parameter containing <code>openid</code>, and the <code>response_type</code> having the value <code>code</code>, the <code>scope</code> parameter MUST also include <code>bound_key</code>, and the request MUST include the <code>dpop_jkt</code> parameter having the value of the JWK Thumbprint <span>[<a href="#RFC7638" class="cite xref">RFC7638</a>]</span> of the proof-of-possession public key using the SHA-256 hash function, as defined in <span>[<a href="#RFC9449" class="cite xref">RFC9449</a>]</span> section 10.<a href="#section-1.5-1" class="pilcrow">¶</a></p>
<p id="section-1.5-2">Following is a non-normative example of an authentication request using the authorization code flow:<a href="#section-1.5-2" class="pilcrow">¶</a></p>
<div class="alignLeft art-text artwork" id="section-1.5-3">
<pre>GET /authorize?
response_type=code
&dpop_jkt=1f2e6338febe335e2cbaa7c7154c3cbdcfd8650f95c5fe7206bb6360e37f4b5a
&scope=openid%20profile%20email%20bound_key
&client_id=s6BhdRkqt3
&state=af0ifjsldkj
&nonce=2a50f9ea812f9bb4c8f7
&redirect_uri=https%3A%2F%2Fclient.example.org%2Fcb HTTP/1.1
Host: server.example.com
</pre><a href="#section-1.5-3" class="pilcrow">¶</a>
</div>
<p id="section-1.5-4">If the OP does not support the <code>bound_key</code> scope, it SHOULD ignore it per <span>[<a href="#OpenID.Core" class="cite xref">OpenID.Core</a>]</span> 3.1.2.1.<a href="#section-1.5-4" class="pilcrow">¶</a></p>
</section>
</div>
<div id="authentication-request-device-authorization-flow">
<section id="section-1.6">
<h3 id="name-authentication-request-devi">
<a href="#section-1.6" class="section-number selfRef">1.6. </a><a href="#name-authentication-request-devi" class="section-name selfRef">Authentication Request - Device Authorization Flow</a>
</h3>
<p id="section-1.6-1">If the RP authenticating component is running on a device that does not support a web browser, it makes an authorization request per <span>[<a href="#RFC8628" class="cite xref">RFC8628</a>]</span> 3.1. In the request, the <code>scope</code> parameter MUST contain both <code>openid</code> and <code>bound_key</code>. The request MUST include the <code>dpop_jkt</code> parameter having the value of the JWK Thumbprint <span>[<a href="#RFC7638" class="cite xref">RFC7638</a>]</span> of the proof-of-possession public key using the SHA-256 hash function, as defined in <span>[<a href="#RFC9449" class="cite xref">RFC9449</a>]</span> section 10.<a href="#section-1.6-1" class="pilcrow">¶</a></p>
<p id="section-1.6-2">Following is a non-normative example of an authentication request using the device authorization flow:<a href="#section-1.6-2" class="pilcrow">¶</a></p>
<div class="alignLeft art-text artwork" id="section-1.6-3">
<pre>TBD
</pre><a href="#section-1.6-3" class="pilcrow">¶</a>
</div>
<p id="section-1.6-4">If the OP does not support the <code>bound_key</code> scope, it SHOULD ignore it per <span>[<a href="#OpenID.Core" class="cite xref">OpenID.Core</a>]</span> 3.1.2.1.<a href="#section-1.6-4" class="pilcrow">¶</a></p>
</section>
</div>
<div id="authentication-response">
<section id="section-1.7">
<h3 id="name-authentication-response">
<a href="#section-1.7" class="section-number selfRef">1.7. </a><a href="#name-authentication-response" class="section-name selfRef">Authentication Response</a>
</h3>
<p id="section-1.7-1">If the key provided was not previously bound to the client, the OP SHOULD inform a user and obtain consent that a key binding will be done.<a href="#section-1.7-1" class="pilcrow">¶</a></p>
<p id="section-1.7-2">On successful authentication of, and consent from the user, the OP returns an authorization <code>code</code>.<a href="#section-1.7-2" class="pilcrow">¶</a></p>
<p id="section-1.7-3">Following is a non-normative example of a response:<a href="#section-1.7-3" class="pilcrow">¶</a></p>
<div class="alignLeft art-text artwork" id="section-1.7-4">
<pre>TBD
</pre><a href="#section-1.7-4" class="pilcrow">¶</a>
</div>
</section>
</div>
<div id="token-request">
<section id="section-1.8">
<h3 id="name-token-request">
<a href="#section-1.8" class="section-number selfRef">1.8. </a><a href="#name-token-request" class="section-name selfRef">Token Request</a>
</h3>
<p id="section-1.8-1">To obtain the ID Token, the RP authenticating component:<a href="#section-1.8-1" class="pilcrow">¶</a></p>
<ol start="1" type="1" class="normal type-1" id="section-1.8-2">
<li id="section-1.8-2.1">
<p id="section-1.8-2.1.1">generates a <code>c_hash</code> by computing a SHA256 hash of the authorization <code>code</code><a href="#section-1.8-2.1.1" class="pilcrow">¶</a></p>
</li>
<li id="section-1.8-2.2">
<p id="section-1.8-2.2.1">converts the hash to BASE64URL<a href="#section-1.8-2.2.1" class="pilcrow">¶</a></p>
</li>
<li id="section-1.8-2.3">
<p id="section-1.8-2.3.1">generates a <code>DPoP</code> header, including the <code>c_hash</code> claim in the <code>DPoP</code> header JWT. This binds the authorization code to the token request.<a href="#section-1.8-2.3.1" class="pilcrow">¶</a></p>
</li>
</ol>
<p id="section-1.8-3">Non-normative example:<a href="#section-1.8-3" class="pilcrow">¶</a></p>
<div class="alignLeft art-text artwork" id="section-1.8-4">
<pre>POST /token HTTP/1.1
Host: server.example.com
Content-Type: application/x-www-form-urlencoded
Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW
DPoP: eyJhbGciOiJFUzI1NiJ9.eyJ0eXAiOiJkcG9wK2p3dCIsImFsZyI6IkV\
TMjU2IiwiandrIjp7ImNydiI6IlAtMjU2Iiwia3R5IjoiRUMiLCJ4IjoibWptR\
m1MZm9wVmkwZXRfYTZmZFhUTnJqYVUwR1dlZFN0Y3NfRzU4OEkyMCIsInkiOiJ\
sMFZwRXlSYzdTdUpfdHFhd2NaQ2VLLXVUOEVPVnF4N3NqTHJGeUJTUllZIn0sI\
m5vbmNlIjoiU3BseGxPQmVaUVFZYllTNld4U2JJQSJ9.cp8uN3kHAMS9fhGH7T\
vTSKwH5oNJzAeMhIrgD_HQHGhgt_N1xQHdHiMkn7AMj3UDkwoNOW4Qqak
grant_type=authorization_code&code=SplxlOBeZQQYbYS6WxSbIA
&redirect_uri=https%3A%2F%2Fclient.example.org%2Fcb
</pre><a href="#section-1.8-4" class="pilcrow">¶</a>
</div>
<p id="section-1.8-5">If a DPoP header is included in the token request to the OP, and the <code>dpop_jkt</code> parameter was not included in the authentication request, the OP MUST NOT include the <code>cnf</code> claim in the ID Token.<a href="#section-1.8-5" class="pilcrow">¶</a></p>
<ul class="normal ulEmpty">
<li class="normal ulEmpty" id="section-1.8-6.1">
<p id="section-1.8-6.1.1">This prevents an existing deployment using DPoP for access token from having them included in ID Tokens accidentally.<a href="#section-1.8-6.1.1" class="pilcrow">¶</a></p>
</li>
</ul>
<p id="section-1.8-7">The OP MUST:
- perform all verification steps as described in <span>[<a href="#RFC9449" class="cite xref">RFC9449</a>]</span> section 5.
- calculate the <code>c_hash</code> from the authorization <code>code</code> just as the RP component did.
- confirm the <code>c_hash</code> in the DPoP JWT matches its calculated <code>c_hash</code><a href="#section-1.8-7" class="pilcrow">¶</a></p>
</section>
</div>
<div id="token-response">
<section id="section-1.9">
<h3 id="name-token-response">
<a href="#section-1.9" class="section-number selfRef">1.9. </a><a href="#name-token-response" class="section-name selfRef">Token Response</a>
</h3>
<p id="section-1.9-1">If the token request was successful, the OP MUST return an ID Token containing the <code>cnf</code> claim as defined in <span>[<a href="#RFC7800" class="cite xref">RFC7800</a>]</span> set to the jwk of the user's public key and with <code>typ</code> set to <code>id_token+cnf</code> in the ID Token's protected header.<a href="#section-1.9-1" class="pilcrow">¶</a></p>
<p id="section-1.9-2">Non-normative example of the ID Token payload:<a href="#section-1.9-2" class="pilcrow">¶</a></p>
<div class="alignLeft art-json art-text artwork" id="section-1.9-3">
<pre>{
"iss": "https://server.example.com",
"sub": "24400320",
"aud": "s6BhdRkqt3",
"nonce": "n-0S6_WzA2Mj",
"exp": 1311281970,
"iat": 1311280970,
"cnf":
{
"jwk": {
"alg":"ES256",
"crv": "P-256",
"kty": "EC",
"x": "mjmFmLfopVi0et_a6fdXTNrjaU0GWedStcs_G588I20",
"y": "l0VpEyRc7SuJ_tqawcZCeK-uT8EOVqx7sjLrFyBSRYY"
}
}
}
</pre><a href="#section-1.9-3" class="pilcrow">¶</a>
</div>
</section>
</div>
<div id="id-token-proof-of-possession">
<section id="section-1.10">
<h3 id="name-id-token-proof-of-possessio">
<a href="#section-1.10" class="section-number selfRef">1.10. </a><a href="#name-id-token-proof-of-possessio" class="section-name selfRef">ID Token Proof of Possession</a>
</h3>
<p id="section-1.10-1">The mechanism for how an RP authenticating component proves to an RP consuming component that it possesses the private keys associated with the <code>cnf</code> claim in the ID Token is out of scope of this document.<a href="#section-1.10-1" class="pilcrow">¶</a></p>
<ul class="normal ulEmpty">
<li class="normal ulEmpty" id="section-1.10-2.1">
<p id="section-1.10-2.1.1">If the WG wants to, we can also profile how to use KB to bind a proof of possession to an ID Token for presentation when a proof of possesion is not present.<a href="#section-1.10-2.1.1" class="pilcrow">¶</a></p>
</li>
</ul>
</section>
</div>
</section>
</div>
<div id="privacy-considerations">
<section id="section-2">
<h2 id="name-privacy-considerations">
<a href="#section-2" class="section-number selfRef">2. </a><a href="#name-privacy-considerations" class="section-name selfRef">Privacy Considerations</a>
</h2>
<p id="section-2-1">An RP authenticating component SHOULD only share an ID Token with a consuming component when such sharing is consistent with the original purpose for which the PII was collected and the scope of consent obtained from the user.<a href="#section-2-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="security-considerations">
<section id="section-3">
<h2 id="name-security-considerations">
<a href="#section-3" class="section-number selfRef">3. </a><a href="#name-security-considerations" class="section-name selfRef">Security Considerations</a>
</h2>
<div id="require-proof-of-possesion">
<section id="section-3.1">
<h3 id="name-require-proof-of-possesion">
<a href="#section-3.1" class="section-number selfRef">3.1. </a><a href="#name-require-proof-of-possesion" class="section-name selfRef">Require Proof of Possesion</a>
</h3>
<p id="section-3.1-1">An RP consuming component MUST NOT trust an ID Token with a <code>cnf</code> claim without a corresponding proof of possession from the RP authenticating component.<a href="#section-3.1-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="id-token-reverification">
<section id="section-3.2">
<h3 id="name-id-token-reverification">
<a href="#section-3.2" class="section-number selfRef">3.2. </a><a href="#name-id-token-reverification" class="section-name selfRef">ID Token Reverification</a>
</h3>
<p id="section-3.2-1">In addition to verifying the signature created by the RP authenticating component to prove possession of the private key associated with the <code>cnf</code> claim in the ID Token, an RP consuming component MUST independently verify the signature and validity of the ID Token and that the <code>aud</code> claim in the payload is the correct value, and that the <code>typ</code> claim in the protected header is <code>id_token+cnf</code>.<a href="#section-3.2-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="use-as-access-token">
<section id="section-3.3">
<h3 id="name-use-as-access-token">
<a href="#section-3.3" class="section-number selfRef">3.3. </a><a href="#name-use-as-access-token" class="section-name selfRef">Use as Access Token</a>
</h3>
<p id="section-3.3-1">The ID Token MUST NOT be used as an access token to access resources. The RP MAY exchange the ID Token with a proof of possesion for an access token that can then be used to access resources.<a href="#section-3.3-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="unique-key-pair">
<section id="section-3.4">
<h3 id="name-unique-key-pair">
<a href="#section-3.4" class="section-number selfRef">3.4. </a><a href="#name-unique-key-pair" class="section-name selfRef">Unique Key Pair</a>
</h3>
<p id="section-3.4-1">To prevent token confusion attacks, the RP authenticating component SHOULD bind a unique key pair to its ID Tokens, and not use it for other purposes.<a href="#section-3.4-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="using-cnf-as-a-user-claim">
<section id="section-3.5">
<h3 id="name-using-cnf-as-a-user-claim">
<a href="#section-3.5" class="section-number selfRef">3.5. </a><a href="#name-using-cnf-as-a-user-claim" class="section-name selfRef">Using cnf as a User Claim</a>
</h3>
<p id="section-3.5-1">The <code>cnf</code> claim in the ID Token MUST be verified together with proof of possession and MUST NOT be treated as proof on its own. A proof of possession is REQUIRED to establish that a party controls the key identified by <code>cnf</code>. The <code>cnf</code> claim SHOULD only be used to bind a signed object with the other claims in the ID Token.<a href="#section-3.5-1" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="iana-considerations">
<section id="section-4">
<h2 id="name-iana-considerations">
<a href="#section-4" class="section-number selfRef">4. </a><a href="#name-iana-considerations" class="section-name selfRef">IANA Considerations</a>
</h2>
<p id="section-4-1">The following entry should be added to the "Media Types" registry for the new JWT type:<a href="#section-4-1" class="pilcrow">¶</a></p>
<p id="section-4-2">Type name: application<a href="#section-4-2" class="pilcrow">¶</a></p>
<p id="section-4-3">Subtype name: dpop+id_token<a href="#section-4-3" class="pilcrow">¶</a></p>
</section>
</div>
<section id="section-5">
<h2 id="name-references">
<a href="#section-5" class="section-number selfRef">5. </a><a href="#name-references" class="section-name selfRef">References</a>
</h2>
<section id="section-5.1">
<h3 id="name-normative-references">
<a href="#section-5.1" class="section-number selfRef">5.1. </a><a href="#name-normative-references" class="section-name selfRef">Normative References</a>
</h3>
<dl class="references">
<dt id="OpenID.Core">[OpenID.Core]</dt>
<dd>
<span class="refAuthor">Sakimura, N.</span>, <span class="refAuthor">Jones, M.</span>, and <span class="refAuthor">J. Bradley</span>, <span class="refTitle">"OpenID Connect Core 1.0 (incorporating errata set 2)"</span>, <time datetime="2023-12-15" class="refDate">15 December 2023</time>, <span><<a href="https://openid.net/specs/openid-connect-core-1_0.html">https://openid.net/specs/openid-connect-core-1_0.html</a>></span>. </dd>
<dd class="break"></dd>
<dt id="OpenID.Discovery">[OpenID.Discovery]</dt>
<dd>
<span class="refAuthor">Sakimura, N.</span>, <span class="refAuthor">Jones, M.</span>, <span class="refAuthor">Bradley, J.</span>, and <span class="refAuthor">E. Jay</span>, <span class="refTitle">"OpenID Connect Discovery 1.0 (incorporating errata set 2)"</span>, <time datetime="2023-12-15" class="refDate">15 December 2023</time>, <span><<a href="https://openid.net/specs/openid-connect-discovery-1_0.html">https://openid.net/specs/openid-connect-discovery-1_0.html</a>></span>. </dd>
<dd class="break"></dd>
<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><<a href="https://www.rfc-editor.org/info/rfc2119">https://www.rfc-editor.org/info/rfc2119</a>></span>. </dd>
<dd class="break"></dd>
<dt id="RFC7638">[RFC7638]</dt>
<dd>
<span class="refAuthor">Jones, M.</span> and <span class="refAuthor">N. Sakimura</span>, <span class="refTitle">"JSON Web Key (JWK) Thumbprint"</span>, <span class="seriesInfo">RFC 7638</span>, <span class="seriesInfo">DOI 10.17487/RFC7638</span>, <time datetime="2015-09" class="refDate">September 2015</time>, <span><<a href="https://www.rfc-editor.org/info/rfc7638">https://www.rfc-editor.org/info/rfc7638</a>></span>. </dd>
<dd class="break"></dd>
<dt id="RFC7800">[RFC7800]</dt>
<dd>
<span class="refAuthor">Jones, M.</span>, <span class="refAuthor">Bradley, J.</span>, and <span class="refAuthor">H. Tschofenig</span>, <span class="refTitle">"Proof-of-Possession Key Semantics for JSON Web Tokens (JWTs)"</span>, <span class="seriesInfo">RFC 7800</span>, <span class="seriesInfo">DOI 10.17487/RFC7800</span>, <time datetime="2016-04" class="refDate">April 2016</time>, <span><<a href="https://www.rfc-editor.org/info/rfc7800">https://www.rfc-editor.org/info/rfc7800</a>></span>. </dd>
<dd class="break"></dd>
<dt id="RFC8626">[RFC8626]</dt>
<dd>
<span class="refTitle">"Not Issued"</span>, <span class="seriesInfo">RFC 8626</span>, <span><<a href="https://www.rfc-editor.org/info/rfc8626">https://www.rfc-editor.org/info/rfc8626</a>></span>. </dd>
<dd class="break"></dd>
<dt id="RFC8628">[RFC8628]</dt>
<dd>
<span class="refAuthor">Denniss, W.</span>, <span class="refAuthor">Bradley, J.</span>, <span class="refAuthor">Jones, M.</span>, and <span class="refAuthor">H. Tschofenig</span>, <span class="refTitle">"OAuth 2.0 Device Authorization Grant"</span>, <span class="seriesInfo">RFC 8628</span>, <span class="seriesInfo">DOI 10.17487/RFC8628</span>, <time datetime="2019-08" class="refDate">August 2019</time>, <span><<a href="https://www.rfc-editor.org/info/rfc8628">https://www.rfc-editor.org/info/rfc8628</a>></span>. </dd>
<dd class="break"></dd>
<dt id="RFC9449">[RFC9449]</dt>
<dd>
<span class="refAuthor">Fett, D.</span>, <span class="refAuthor">Campbell, B.</span>, <span class="refAuthor">Bradley, J.</span>, <span class="refAuthor">Lodderstedt, T.</span>, <span class="refAuthor">Jones, M.</span>, and <span class="refAuthor">D. Waite</span>, <span class="refTitle">"OAuth 2.0 Demonstrating Proof of Possession (DPoP)"</span>, <span class="seriesInfo">RFC 9449</span>, <span class="seriesInfo">DOI 10.17487/RFC9449</span>, <time datetime="2023-09" class="refDate">September 2023</time>, <span><<a href="https://www.rfc-editor.org/info/rfc9449">https://www.rfc-editor.org/info/rfc9449</a>></span>. </dd>
<dd class="break"></dd>
</dl>
</section>
<section id="section-5.2">
<h3 id="name-informative-references">
<a href="#section-5.2" class="section-number selfRef">5.2. </a><a href="#name-informative-references" class="section-name selfRef">Informative References</a>
</h3>
<dl class="references">
<dt id="IANA.JOSE.ALGS">[IANA.JOSE.ALGS]</dt>
<dd>
<span class="refAuthor">IANA</span>, <span class="refTitle">"IANA JSON Web Signature and Encryption Algorithms Registry"</span>, <time datetime="2025" class="refDate">2025</time>, <span><<a href="https://www.iana.org/assignments/jose/jose.xhtml#web-signature-encryption-algorithms">https://www.iana.org/assignments/jose/jose.xhtml#web-signature-encryption-algorithms</a>></span>. </dd>
<dd class="break"></dd>
</dl>
</section>
</section>
<div id="acknowledgements">
<section id="appendix-A">
<h2 id="name-acknowledgements">
<a href="#appendix-A" class="section-number selfRef">Appendix A. </a><a href="#name-acknowledgements" class="section-name selfRef">Acknowledgements</a>
</h2>
<p id="appendix-A-1">The authors would like to thank early feedback provided by Filip Skokan, George Fletcher, Jacob Ideskog, and Kosuke Koiwai.<a href="#appendix-A-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="notices">
<section id="appendix-B">
<h2 id="name-notices">
<a href="#appendix-B" class="section-number selfRef">Appendix B. </a><a href="#name-notices" class="section-name selfRef">Notices</a>
</h2>
<p id="appendix-B-1"><em>To be completed if adopted.</em><a href="#appendix-B-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="document-history">
<section id="appendix-C">
<h2 id="name-document-history">
<a href="#appendix-C" class="section-number selfRef">Appendix C. </a><a href="#name-document-history" class="section-name selfRef">Document History</a>
</h2>
<p id="appendix-C-1">[[ To be removed from the final specification ]]<a href="#appendix-C-1" class="pilcrow">¶</a></p>
<p id="appendix-C-2">-00<a href="#appendix-C-2" class="pilcrow">¶</a></p>
<p id="appendix-C-3">initial draft<a href="#appendix-C-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="authors-addresses">
<section id="appendix-D">
<h2 id="name-authors-addresses">
<a href="#name-authors-addresses" class="section-name selfRef">Authors' Addresses</a>
</h2>
<address class="vcard">
<div dir="auto" class="left"><span class="fn nameRole">Dick Hardt</span></div>
<div dir="auto" class="left"><span class="org">Hellō</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:dick.hardt@gmail.com" class="email">dick.hardt@gmail.com</a>
</div>
</address>
<address class="vcard">
<div dir="auto" class="left"><span class="fn nameRole">Ethan Heilman</span></div>
<div dir="auto" class="left"><span class="org">Cloudflare</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:ethan.r.heilman@gmail.com" class="email">ethan.r.heilman@gmail.com</a>
</div>
</address>
</section>
</div>
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