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<rfc category="std" xmlns:xi="http://www.w3.org/2001/XInclude" docName="draft-ietf-oauth-jwt-introspection-response-12"
     ipr="trust200902">
  <!--
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	--> number="9701" ipr="trust200902" obsoletes="" updates="" submissionType="IETF" category="std" consensus="true" xml:lang="en" tocInclude="true" tocDepth="4" symRefs="true" sortRefs="true" version="3">

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<front>
    <!--
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    <title abbrev="JWT Response">JWT Response">JSON Web Token (JWT) Response for OAuth Token Introspection</title>
    <seriesInfo name="RFC" value="9701"/>
    <author fullname="Torsten Lodderstedt" initials="T." role="editor" surname="Lodderstedt">
      <organization>yes.com AG</organization>
      <address>
        <email>torsten@lodderstedt.net</email>

        <!-- uri and facsimile elements may also be added -->
      </address>
    </author>
    <author fullname="Vladimir Dzhuvinov" initials="V." surname="Dzhuvinov">
      <organization>Connect2id Ltd.</organization>
      <address>
        <email>vladimir@connect2id.com</email>

        <!-- uri and facsimile elements may also be added -->
      </address>
    </author>
    <date day="04" month="Sep" year="2021" />

    <!-- Meta-data Declarations --> month="December" year="2024"/>
    <area>Security Area</area>
    <workgroup>Open Authentication Protocol</workgroup>

    <!--
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			individual submissions. If this element is not present, the default
			is "Network Working Group", which is used by the RFC Editor as a nod
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    <keyword>token introspection</keyword>
    <keyword>JWT</keyword>
    <keyword>oauth2</keyword>

    <!--
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    <abstract>
      <t>This specification proposes an additional response secured by JSON Web Token (JWT) secured response
      for OAuth 2.0 Token Introspection.</t>
    </abstract>
  </front>
  <middle>
    <section anchor="Introduction" title="Introduction"> numbered="true" toc="default">
      <name>Introduction</name>
      <t><xref target="RFC7662">OAuth target="RFC7662" format="default">"OAuth 2.0 Token Introspection</xref> Introspection"</xref> specifies a
      method for a protected resource to query an OAuth 2.0 authorization server
      to determine the state of an access token and obtain data associated with
      the access token. This enables deployments to implement opaque access
      tokens in an interoperable way.</t>
      <t>The introspection response, as specified in <xref target="RFC7662">OAuth target="RFC7662" format="default">"OAuth
      2.0 Token Introspection</xref>, Introspection"</xref>, is a plain JSON object.
      However, there are use cases where the resource server requires stronger
      assurance that the authorization server issued the token introspection
      response for an access token, including cases where the authorization server
      assumes liability for the content of the token introspection response.
      An example is a resource server using verified person personal data to create certificates,
      which in turn are used to create qualified electronic signatures.</t>
      <t>In such use cases cases, it may be useful or even required to return a
      signed <xref target="RFC7519">JWT</xref> target="RFC7519" format="default">JWT</xref> as the introspection response.
      This specification extends the token introspection endpoint with the capability
      to return responses as JWTs.</t>
    </section>
    <section anchor="RNC" title="Requirements Notation and Conventions"> numbered="true" toc="default">
      <name>Requirements Notation</name>
        <t>
    The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
  "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>",
    "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL NOT</bcp14>",
    "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>",
    "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
    "<bcp14>MAY</bcp14>", and "OPTIONAL" "<bcp14>OPTIONAL</bcp14>" in this document are to be
    interpreted as described in
  BCP 14 BCP&nbsp;14 <xref target="RFC2119"/> <xref
    target="RFC8174"/> when, and only when, they appear in all capitals, as
    shown here.
        </t>
    </section>
    <section anchor="as-rs-relationship" title="Resource numbered="true" toc="default">
      <name>Resource Server Management"> Management</name>
      <t>The authorization server (AS) and the resource server (RS) maintain a strong strong, two-way trust relationship.
    The resource server relies on the authorization server to obtain authorization,
    user
    user, and other data as input to its access control decisions and service delivery.
    The authorization server relies on the resource server to handle the provided data
    appropriately.</t>
      <t>In the context of this specification, the token introspection endpoint is used to convey
    such security data and potentially also privacy sensitive privacy-sensitive data related to an access
    token.</t>
      <t>In order to process the introspection requests in a secure and
    privacy-preserving manner, the authorization server MUST <bcp14>MUST</bcp14> be able to identify,
    authenticate
    authenticate, and authorize resource servers.</t>
      <t>The authorization server MAY AS <bcp14>MAY</bcp14> additionally encrypt the token introspection response JWTs.
    If encryption is used used, the authorization server AS is provisioned with encryption keys and
    algorithms for the RS.</t>
      <t>The authorization server MUST AS <bcp14>MUST</bcp14> be able to determine whether an RS is the
    audience for a particular access token and what data it is entitled to receive,
    otherwise receive;
    otherwise, the RS is not authorized to obtain data for the access token.
    The AS has the discretion of how to fulfil fulfill this requirement. The AS could, for example,
    maintain a mapping between scope values and resource servers.</t> RSs.</t>
      <t>The requirements given above imply that the authorization server AS
    maintains credentials and other configuration data for each RS.</t>
      <t>One way is by utilizing dynamic client registration <xref target="RFC7591"/> target="RFC7591" format="default"/>
    and treating every RS as an OAuth client. In this case, the authorization server AS
    is assumed to at least maintain a "client_id" and a "token_endpoint_auth_method"
    with complementary authentication method metadata, such as "jwks" or "client_secret".
    In cases where the AS needs to acquire consent to transmit data to a an RS, the following
    client metadata fields are recommended: "client_name", "client_uri", "contacts",
    "tos_uri", and "policy_uri".</t>
      <t>The AS MUST <bcp14>MUST</bcp14> restrict the use of client credentials by a an RS to the calls
    it requires, e.g. e.g., the AS MAY <bcp14>MAY</bcp14> restrict such a client to call
    the token introspection endpoint only. How the AS implements this restriction
    is beyond the scope of this specification.</t>
      <t>This specification further introduces client metadata to manage the
    configuration options required to sign and encrypt token introspection
    response JWTs.</t>
    </section>
    <section anchor="jwt_request" title="Requesting numbered="true" toc="default">
      <name>Requesting a JWT Response">

	<t>A resource server Response</name>
      <t>An RS requests a JWT introspection response by sending an introspection request
    with an <spanx style="verb">Accept</spanx> <tt>Accept</tt> HTTP header field set to
      "application/token-introspection+jwt".</t>
      <t>The AS MUST <bcp14>MUST</bcp14> authenticate the caller at the token introspection endpoint. Authentication can
    utilize client authentication methods or a separate access token that is issued to the resource server RS
    and identifying it identifies the RS as the subject.</t>
      <t>The following is a non-normative example request, with the resource
    server RS authenticating with a private key JWT:</t>

	  <t>
	  	<figure>
          <artwork><![CDATA[POST
    <sourcecode name="" type="http-message"><![CDATA[
POST /introspect HTTP/1.1
Host: as.example.com
Accept: application/token-introspection+jwt
Content-Type: application/x-www-form-urlencoded

token=2YotnFZFEjr1zCsicMWpAA&
client_assertion_type=
 urn%3Aietf%3Aparams%3Aoauth%3Aclient-assertion-type%3Ajwt-bearer&
 client_assertion=PHNhbWxwOl[...omitted for brevity...]ZT]]></artwork>
        </figure>
	  </t> brevity...]ZT
]]></sourcecode>
    </section>
    <section anchor="jwt_response" title="JWT Response"> numbered="true" toc="default">
      <name>JWT Response</name>
      <t>The introspection endpoint responds with a JWT, setting the
     <spanx style="verb">Content-Type</spanx>
     <tt>Content-Type</tt> HTTP header field to
     "application/token-introspection+jwt" and the JWT <spanx style="verb">typ</spanx> <tt>typ</tt>
     ("type") header parameter to "token-introspection+jwt".</t>
      <t>The JWT MUST <bcp14>MUST</bcp14> include the following top-level claims:
     <list hangIndent="8" style="hanging">
         <t hangText="iss">MUST
      </t>
      <dl newline="true" spacing="normal">
        <dt>iss</dt>
        <dd><bcp14>MUST</bcp14> be set to the issuer URL of the authorization
         server.</t>
         <t hangText="aud">MUST
         server.</dd>
        <dt>aud</dt>
        <dd><bcp14>MUST</bcp14> identify the resource server receiving the token
         introspection response.</t>
         <t hangText="iat">MUST response.</dd>
        <dt>iat</dt>
        <dd><bcp14>MUST</bcp14> be set to the time when the introspection response
         was created by the authorization server.</t>
         <t hangText="token_introspection">A server</dd>
        <dt>token_introspection</dt>
        <dd>
         <t>A JSON object containing the members of the token introspection response response, as specified
	 in <xref target="RFC7662"/>, section 2.2. target="RFC7662" section="2.2" sectionFormat="comma" format="default"/>.
         The separation of the introspection response members into
         a dedicated JSON object containing a JWT claim is intended to prevent conflict and confusion
         with top-level JWT claims that may bear the same name.
         <vspace blankLines="1" />
          </t>
          <t>
         If the access token is invalid, expired, revoked, or not intended for the
         calling resource server (audience), the authorization server MUST <bcp14>MUST</bcp14> set the value of the
         <spanx style="verb">active</spanx>
         <tt>active</tt> member in the <spanx style="verb">token_introspection</spanx> <tt>token_introspection</tt>
         claim to <spanx style="verb">false</spanx> <tt>false</tt> and MUST NOT <bcp14>MUST NOT</bcp14> include other members.
         Otherwise, the <spanx style="verb">active</spanx> <tt>active</tt> member is set to <spanx style="verb">true</spanx>.
         <vspace blankLines="1" /> <tt>true</tt>.
          </t>
          <t>
         The AS SHOULD <bcp14>SHOULD</bcp14> narrow down the <spanx style="verb">scope</spanx> <tt>scope</tt> value to the scopes
         relevant to the particular RS.
         <vspace blankLines="1" />
          </t>
          <t>
         As specified in section 2.2 of <xref target="RFC7662"/>, target="RFC7662" section="2.2" sectionFormat="of" format="default"/>, implementations MAY <bcp14>MAY</bcp14> extend the
         token introspection response with service-specific claims. In the context of this
         specification, such claims will be added as top-level members of the
         <spanx style="verb">token_introspection</spanx>
         <tt>token_introspection</tt> claim.
         <vspace blankLines="1" />
          </t>
          <t>
         Token introspection response parameter names intended to be used across domains MUST <bcp14>MUST</bcp14> be
         registered in the <xref target="IANA.OAuth.Token.Introspection">OAuth target="IANA.OAuth.Token.Introspection" format="default">"OAuth Token Introspection
         Response
         Response" registry</xref> defined by <xref target="RFC7662"/>.
         <vspace blankLines="1" /> target="RFC7662" format="default"/>.
          </t>
          <t>
         When the AS acts as a provider of resource owner
         identity claims to the RS, the AS determines determines, based on its RS-specific policy policy, what
         identity claims to return in the token introspection response.
         The AS MUST <bcp14>MUST</bcp14> ensure the release of any privacy-sensitive data is legally based (see
         <xref target="privacy"/>).
         <vspace blankLines="1" /> target="privacy" format="default"/>).
          </t>
          <t>
         Further content of the introspection response is determined by the RS-specific
         policy at the AS.</t>
     </list>
     </t>
        </dd>
      </dl>
      <t>The JWT MAY <bcp14>MAY</bcp14> include other claims, including those from the
      "JSON Web Token Claims" registry established by <xref target="RFC7519"/>. target="RFC7519"
      format="default"/>. The JWT SHOULD NOT <bcp14>SHOULD NOT</bcp14> include the
     <spanx style="verb">sub</spanx>
      <tt>sub</tt> and <spanx style="verb">exp</spanx> <tt>exp</tt> claims, as an additional prevention against measure to prevent misuse of the JWT as an access token (see
      <xref target="Cross-JWT_Confusion"/>).</t> target="Cross-JWT_Confusion" format="default"/>).</t>
      <t>Note: Although the JWT format is widely used as an access token format, the JWT
     returned in the introspection response is not an alternative representation of
     the introspected access token and is not intended to be used as an access token.</t>
      <t>This specification registers the "application/token-introspection+jwt" media type,
     which is used as the value of the <spanx style="verb">typ</spanx> <tt>typ</tt> ("type") header
     parameter of the JWT to indicate that the payload is a token introspection response.</t>
      <t>The JWT is cryptographically secured as specified in <xref target="RFC7519"/>.</t> target="RFC7519" format="default"/>.</t>
      <t>Depending on the specific resource server policy policy, the JWT is either
     signed,
     signed or signed and encrypted. If the JWT is signed and encrypted encrypted, it
     MUST
     <bcp14>MUST</bcp14> be a Nested JWT, as defined in <xref target="RFC7519">JWT</xref>.</t> target="RFC7519" format="default">JWT</xref>.</t>
      <t>Note: An AS compliant with this specification MUST <bcp14>MUST</bcp14> refuse to serve introspection
     requests that don't authenticate the caller, caller and return an HTTP status code 400. This is
     done to ensure token data is released to legitimate recipients only and prevent
     downgrading to <xref target="RFC7662"/> target="RFC7662" format="default"/> behavior (see
     <xref target="token_data_leakage"/>).</t> target="token_data_leakage" format="default"/>).</t>
      <t>The following is a non-normative example response
     (with line breaks for display purposes only):</t>

	 <t>
	  	<figure>
          <artwork><![CDATA[HTTP/1.1
     <sourcecode name="" type="http-message"><![CDATA[
HTTP/1.1 200 OK
Content-Type: application/token-introspection+jwt

eyJraWQiOiJ3RzZEIiwidHlwIjoidG9rZW4taW50cm9zcGVjdGlvbitqd3QiLCJhbGc
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eyqmru6lKlASOsaE8dmLSeKcX91FbG79FKN8un24iwIDCbKT9xlUFl54xWVShNDFA]]></artwork>
        </figure>
        </t>
eyqmru6lKlASOsaE8dmLSeKcX91FbG79FKN8un24iwIDCbKT9xlUFl54xWVShNDFA
]]></sourcecode>
      <t>
        The example response JWT header contains the following JSON document:
      </t>
        <t>
        <figure>
          <artwork><![CDATA[{
<sourcecode name="" type="json"><![CDATA[
{
  "typ": "token-introspection+jwt",
  "alg": "RS256",
  "kid": "wG6D"
}]]></artwork>
        </figure>
        </t>
}
]]></sourcecode>
      <t>
        The example response JWT payload contains the following JSON document:
      </t>
        <t>
        <figure>
          <artwork><![CDATA[{
<sourcecode name="" type="json"><![CDATA[
{
  "iss":"https://as.example.com/",
  "aud":"https://rs.example.com/resource",
  "iat":1514797892,
  "token_introspection":
     {
        "active":true,
        "iss":"https://as.example.com/",
        "aud":"https://rs.example.com/resource",
        "iat":1514797822,
        "exp":1514797942,
        "client_id":"paiB2goo0a",
        "scope":"read write dolphin",
        "sub":"Z5O3upPC88QrAjx00dis",
        "birthdate":"1982-02-01",
        "given_name":"John",
        "family_name":"Doe",
        "jti":"t1FoCCaZd4Xv4ORJUWVUeTZfsKhW30CQCrWDDjwXy6w"
     }
}]]></artwork>
        </figure>

	  </t>
}
]]></sourcecode>
    </section>
    <section anchor="client_metadata" title="Client Metadata"> numbered="true" toc="default">
      <name>Client Metadata</name>
      <t>The authorization server determines the algorithm to
      secure the JWT for a particular introspection response. This decision can
      be based on registered metadata parameters for the resource server,
      supplied via dynamic client registration <xref target="RFC7591"/> target="RFC7591"
      format="default"/> with the
      resource server acting as a client, as specified below.</t>
      <t>The parameter names follow the pattern established by
      <xref target="OpenID.Registration">OpenID target="OpenID.Registration" format="default">OpenID Connect
      Dynamic Client Registration</xref> for configuring signing and encryption
      algorithms for JWT responses at the UserInfo endpoint.</t>
      <t>The following client metadata parameters are introduced by this
      specification:
		<list hangIndent="8" style="hanging">
      	  <t hangText="introspection_signed_response_alg">OPTIONAL.
      </t>
      <dl newline="true" spacing="normal">
        <dt>introspection_signed_response_alg</dt>
        <dd><bcp14>OPTIONAL</bcp14>.
      	  <xref target="RFC7515">JWS</xref> target="RFC7515" format="default">"JSON Web Signature (JWS)"</xref>
      	  algorithm (<spanx style="verb">alg</spanx> value) (<tt>alg</tt> value), as defined in
      	  <xref target="RFC7518">JWA</xref> target="RFC7518" format="default">"JSON Web Algorithms (JWA)"</xref>, for signing
	  introspection responses. If
      	  this is specified, the response will be signed using JWS and the
      	  configured algorithm. The default, if omitted, is <spanx style="verb">RS256</spanx>.</t>
          <t hangText="introspection_encrypted_response_alg">OPTIONAL. <tt>RS256</tt>.</dd>
        <dt>introspection_encrypted_response_alg</dt>
        <dd><bcp14>OPTIONAL</bcp14>.
        <xref target="RFC7516">JWE</xref> target="RFC7516" format="default">"JSON Web Encryption
	(JWE)"</xref> algorithm (<spanx style="verb">alg</spanx> value) (<tt>alg</tt> value),
        as defined in <xref target="RFC7518">JWA</xref> target="RFC7518" format="default">JWA</xref>, for
	content key encryption.
          If this is specified, the response will be encrypted using JWE and the
          configured content encryption algorithm
          (<spanx style="verb">introspection_encrypted_response_enc</spanx>).
          (<tt>introspection_encrypted_response_enc</tt>). The default,
          if omitted, is that no encryption is performed.
          If both signing and
          encryption are requested, the response will be
          signed then encrypted, with the result being a Nested JWT, as defined in
          <xref target="RFC7519">JWT</xref>.</t>
          <t hangText="introspection_encrypted_response_enc">OPTIONAL. target="RFC7519" format="default">JWT</xref>.</dd>
        <dt>introspection_encrypted_response_enc</dt>
        <dd><bcp14>OPTIONAL</bcp14>.
        <xref target="RFC7516">JWE</xref> target="RFC7516" format="default">JWE</xref> algorithm (<spanx style="verb">enc</spanx> value)
	(<tt>enc</tt> value),
        as defined in <xref target="RFC7518">JWA</xref> target="RFC7518" format="default">JWA</xref>, for
	content encryption of
        introspection responses. The default, if omitted, is <spanx style="verb">A128CBC-HS256</spanx>. <tt>A128CBC-HS256</tt>.
          Note: This parameter MUST NOT <bcp14>MUST NOT</bcp14> be specified without setting
          <spanx style="verb">introspection_encrypted_response_alg</spanx>.</t>
        </list>
      </t>
          <tt>introspection_encrypted_response_alg</tt>.</dd>
      </dl>
      <t>Resource servers may register their public encryption keys
      using the <spanx style="verb">jwks_uri</spanx> <tt>jwks_uri</tt> or <spanx style="verb">jwks</spanx> <tt>jwks</tt>
      metadata parameters.</t>
    </section>
    <section anchor="server_metadata" title="Authorization numbered="true" toc="default">
      <name>Authorization Server Metadata"> Metadata</name>
      <t>Authorization servers SHOULD <bcp14>SHOULD</bcp14> publish the supported algorithms for
      signing and encrypting the JWT of an introspection response by utilizing
      <xref target="RFC8414">OAuth target="RFC8414" format="default">"OAuth 2.0 Authorization Server Metadata</xref> Metadata"</xref>
      parameters. Resource servers use this data to parametrize their client
      registration requests.</t>
      <t>The following parameters are introduced by this specification:
		<list hangIndent="8" style="hanging">

		<t hangText="introspection_signing_alg_values_supported">
		OPTIONAL.
      </t>
      <dl newline="true" spacing="normal">
        <dt>introspection_signing_alg_values_supported</dt>
        <dd>
		<bcp14>OPTIONAL</bcp14>. JSON array containing a list of the <xref target="RFC7515">JWS</xref> target="RFC7515" format="default">JWS</xref> signing
		algorithms (<spanx style="verb">alg</spanx> values) (<tt>alg</tt> values), as defined in
		<xref target="RFC7518">JWA</xref> target="RFC7518" format="default">JWA</xref>, supported by the introspection
		endpoint to sign the response.</t>

		<t hangText="introspection_encryption_alg_values_supported">
		OPTIONAL. response.</dd>
        <dt>introspection_encryption_alg_values_supported</dt>
        <dd>
		<bcp14>OPTIONAL</bcp14>. JSON array containing a list of the <xref target="RFC7516">JWE</xref> target="RFC7516" format="default">JWE</xref>
		encryption algorithms (<spanx style="verb">alg</spanx> values) (<tt>alg</tt> values), as defined in
		<xref target="RFC7518">JWA</xref> target="RFC7518" format="default">JWA</xref>, supported by the
		introspection endpoint to encrypt the content encryption key for
		introspection responses (content key encryption).</t>

		<t hangText="introspection_encryption_enc_values_supported">
		OPTIONAL. encryption).</dd>
        <dt>introspection_encryption_enc_values_supported</dt>
        <dd>
		<bcp14>OPTIONAL</bcp14>. JSON array containing a list of the <xref target="RFC7516">JWE</xref> target="RFC7516" format="default">JWE</xref>
		encryption algorithms (<spanx style="verb">enc</spanx> values) (<tt>enc</tt> values), as defined in
		<xref target="RFC7518">JWA</xref> target="RFC7518" format="default">JWA</xref>, supported by the introspection
		endpoint to encrypt the response (content encryption).</t>

        </list>
      </t> encryption).</dd>
      </dl>
    </section>
    <section anchor="Security" title="Security Considerations"> numbered="true" toc="default">
      <name>Security Considerations</name>
      <section anchor="Cross-JWT_Confusion" title="Cross-JWT Confusion"> numbered="true" toc="default">
        <name>Cross-JWT Confusion</name>
        <t>The <spanx style="verb">iss</spanx> <tt>iss</tt> and potentially the <spanx style="verb">aud</spanx> <tt>aud</tt>
      claim of a token introspection JWT can resemble those of a JWT-encoded access token.
      An attacker could try to exploit this and pass a JWT token introspection response as
      an access token to the resource server. The <spanx style="verb">typ</spanx> <tt>typ</tt> ("type")
      JWT header "token-introspection+jwt" and the encapsulation of the token introspection members members,
      such as <spanx style="verb">sub</spanx> <tt>sub</tt> and <spanx style="verb">scope</spanx> <tt>scope</tt> in
      the <spanx style="verb">token_introspection</spanx> claim is <tt>token_introspection</tt> claim, are intended to prevent such
      substitution attacks. Resource servers MUST <bcp14>MUST</bcp14> therefore check the <spanx style="verb">typ</spanx> <tt>typ</tt>
      JWT header value of received JWT-encoded access tokens and ensure all minimally
	required claims for a valid access token are present.</t>
        <t>Resource servers MUST <bcp14>MUST</bcp14> additionally apply the countermeasures against replay access token replay,
      as described in <xref target="I-D.ietf-oauth-security-topics"/>, section 3.2.</t> target="RFC9700" format="default"/>.</t>
        <t>JWT Confusion confusion and other attacks involving JWTs are discussed in
      <xref target="I-D.ietf-oauth-jwt-bcp"/>.</t> target="RFC8725" format="default"/>.</t>
      </section>
      <section anchor="token_data_leakage" title="Token numbered="true" toc="default">
        <name>Token Data Leakage"> Leakage</name>
        <t>The authorization server MUST <bcp14>MUST</bcp14> use Transport Layer Security (TLS) 1.2
      (or higher) higher), per BCP 195 <xref target="RFC7525"/> target="RFC9325" format="default"/>, in order to prevent
      token data leakage.</t>

      <t>Section 2.1 of <xref target="RFC7662"/>
        <t><xref target="RFC7662" section="2.1" sectionFormat="of" format="default"/> permits requests to the introspection endpoint to
      be authorized with an access token which that doesn't identify the caller. To prevent
      introspection of tokens by parties that are not the intended consumer consumer, the
      authorization server MUST <bcp14>MUST</bcp14> require all requests to the token introspection endpoint to be
      authenticated.</t>
      </section>
    </section>
    <section anchor="privacy" title="Privacy Considerations"> numbered="true" toc="default">
      <name>Privacy Considerations</name>
      <t>The token introspection response can be used to transfer personal identifiable
     information (PII) from the AS to the RS. The AS MUST <bcp14>MUST</bcp14> conform to legal and jurisdictional constraints
     for the data transfer before any data is released to a particular RS. The details and determining
     of these constraints varies vary by jurisdiction and is are outside the scope of this document.</t>
      <t>A commonly found way to establish the legal basis for releasing PII is by explicit user
     consent gathered from the resource owner by the AS during the authorization flow.</t>
     <t>It is also possible that the legal basis is established out of band, for example
     example, in an explicit contract or by the client gathering the resource owner's
     consent.</t>
     <t>If the AS and the RS belong to the same legal entity (1st party scenario),
     there is potentially no need for an explicit user consent consent, but the terms of
     service and policy of the respective service provider MUST <bcp14>MUST</bcp14> be
     enforced at all times.</t>
     <t>In any case, the AS MUST <bcp14>MUST</bcp14> ensure that the scope of the legal
     basis is enforced throughout the whole process. The AS MUST <bcp14>MUST</bcp14>
     retain the scope of the legal basis with the access token, e.g. e.g., in the scope
     value, it MUST <bcp14>MUST</bcp14> authenticate the RS, and the AS MUST <bcp14>MUST</bcp14>
     determine the data a resource server an RS is allowed to receive based on the resource server’s RS's identity and suitable token data, e.g.
     e.g., the scope value. </t>
     <t>Implementers should be aware that a token introspection request lets the AS
     know when the client (and potentially the user) is accessing the RS, which is
     also an indication of when the user is using
     the client. If this implication is not acceptable, implementers MUST
     <bcp14>MUST</bcp14> use other means to relay
     access token data, for example example, by directly transferring the data needed by the
     RS within the access token.</t>
    </section>

    <section anchor="Acknowledgements" title="Acknowledgements">
      <t>We would like to thank Petteri Stenius, Neil Madden, Filip Skokan, Tony
      Nadalin, Remco Schaar, Justin Richer, Takahiko Kawasaki, Benjamin Kaduk,
      Robert Wilton and Roman Danyliw for their valuable feedback.</t>
    </section>

    <!-- Possibly a 'Contributors' section ... -->

    <section anchor="IANA" title="IANA Considerations"> numbered="true" toc="default">
      <name>IANA Considerations</name>
      <section anchor="DynRegReg" title="OAuth numbered="true" toc="default">
        <name>OAuth Dynamic Client Registration Metadata Registration"> Registration</name>
        <t>
          This specification requests registration of the
          The following client metadata definitions have been registered
          in the IANA "OAuth Dynamic Client Registration Metadata" registry
          <xref target="IANA.OAuth.Parameters"/> target="IANA.OAuth.Parameters" format="default"/>
          established by <xref target="RFC7591"/>: target="RFC7591" format="default"/>:
        </t>
<section anchor="DynRegContents" title="Registry Contents">
          <t>
            <list style="symbols">
              <t>
                Client numbered="true" toc="default">
          <name>Registry Contents</name>
          <dl newline="false" spacing="compact">
            <dt>Client Metadata Name: <spanx style="verb">introspection_signed_response_alg</spanx>
              </t>
              <t>
                Client Name:</dt>
	    <dd><tt>introspection_signed_response_alg</tt></dd>
            <dt>Client Metadata Description:
                String Description:</dt>
            <dd>String value indicating the client's desired introspection response
            signing algorithm.
              </t>
              <t>
                Change Controller: IESG
              </t>
              <t>
                Specification Document(s): <xref target="client_metadata"/> algorithm</dd>
	    <dt>Change Controller:</dt>
	    <dd>IETF</dd>
            <dt>Reference:</dt>
	    <dd><xref target="client_metadata" format="default"/> of [[ this specification ]]
              </t>
            </list>
          </t>
          <t>
            <list style="symbols">
              <t>
                Client RFC 9701</dd>
          </dl>
          <dl newline="false" spacing="compact">
            <dt>Client Metadata Name: <spanx style="verb">introspection_encrypted_response_alg</spanx>
              </t>
              <t>
                Client Name:</dt>
	    <dd><tt>introspection_encrypted_response_alg</tt></dd>
            <dt>Client Metadata Description:
                String Description:</dt>
            <dd>String value specifying the desired introspection response
            content key encryption algorithm (alg value).
              </t>
              <t>
                Change Controller: IESG
              </t>
              <t>
                Specification Document(s): <xref target="client_metadata"/> value)</dd>
            <dt>Change Controller:</dt>
	    <dd>IETF</dd>
            <dt>Reference:</dt>
	    <dd><xref target="client_metadata" format="default"/> of [[ this specification ]]
              </t>
            </list>
          </t>
          <t>
            <list style="symbols">
              <t>
                Client RFC 9701</dd>
          </dl>
          <dl newline="false" spacing="compact">
            <dt>Client Metadata Name: <spanx style="verb">introspection_encrypted_response_enc</spanx>
              </t>
              <t>
                Client Name:</dt>
	    <dd><tt>introspection_encrypted_response_enc</tt></dd>
            <dt>Client Metadata Description:
                    String Description:</dt>
            <dd>String value specifying the desired introspection response
            content encryption algorithm (enc value).
              </t>
              <t>
                Change Controller: IESG
              </t>
              <t>
                Specification Document(s): <xref target="client_metadata"/> value)</dd>
            <dt>Change Controller:</dt>
	    <dd>IETF</dd>
            <dt>Reference:</dt>
	    <dd><xref target="client_metadata" format="default"/> of [[ this specification ]]
              </t>
            </list>
          </t> RFC 9701</dd>
          </dl>
        </section>
      </section>
      <section anchor="ietf-oauth-discoveryIANA" title="OAuth numbered="true" toc="default">
        <name>OAuth Authorization Server Metadata Registration"> Registration</name>
        <t>
        This specification requests registration of the
        The following values have been registered in
        the IANA "OAuth Authorization Server Metadata" registry
        <xref target="IANA.OAuth.Parameters"/> target="IANA.OAuth.Parameters" format="default"/> established by <xref target="RFC8414"/>. target="RFC8414" format="default"/>.
        </t>
        <section title="Registry Contents">
          <t>
            <list style='symbols'>
              <t>Metadata Name: <spanx style="verb">introspection_signing_alg_values_supported</spanx></t>
              <t>Metadata Description: JSON numbered="true" toc="default">
          <name>Registry Contents</name>
          <dl newline="false" spacing="compact">
            <dt>Metadata Name:</dt>
	    <dd><tt>introspection_signing_alg_values_supported</tt></dd>
            <dt>Metadata Description:</dt>
	    <dd>JSON array containing a list of algorithms supported
            by the authorization server for introspection response signing.</t>
              <t>Change Controller: IESG</t>
              <t>Specification Document(s): <xref target="server_metadata"/> signing</dd>
            <dt>Change Controller:</dt>
	    <dd>IETF</dd>
            <dt>Reference:</dt>
	    <dd><xref target="server_metadata" format="default"/> of [[ this specification ]]</t>
            </list>
          </t>
          <t>
            <list style='symbols'>
              <t>Metadata Name: <spanx style="verb">introspection_encryption_alg_values_supported</spanx></t>
              <t>Metadata Description: JSON RFC 9701</dd>
          </dl>
          <dl newline="false" spacing="compact">
            <dt>Metadata Name:</dt>
	    <dd><tt>introspection_encryption_alg_values_supported</tt></dd>
            <dt>Metadata Description:</dt>
	    <dd>JSON array containing a list of algorithms supported
            by the authorization server for introspection response content key
	    encryption (alg value).</t>
              <t>Change Controller: IESG</t>
              <t>Specification Document(s): <xref target="server_metadata"/> value)</dd>
            <dt>Change Controller:</dt>
	    <dd>IETF</dd>
            <dt>Reference:</dt>
	    <dd><xref target="server_metadata" format="default"/> of [[ this specification ]]</t>
            </list>
          </t>
          <t>
            <list style='symbols'>
              <t>Metadata Name: <spanx style="verb">introspection_encryption_enc_values_supported</spanx></t>
              <t>Metadata Description: JSON RFC 9701</dd>
          </dl>
          <dl newline="false" spacing="compact">
            <dt>Metadata Name:</dt>
	    <dd><tt>introspection_encryption_enc_values_supported</tt></dd>
            <dt>Metadata Description:</dt>
	    <dd>JSON array containing a list of algorithms supported
            by the authorization server for introspection response content
	    encryption (enc value).</t>
              <t>Change Controller: IESG</t>
              <t>Specification Document(s): <xref target="server_metadata"/> value)</dd>
            <dt>Change Controller:</dt>
	    <dd>IETF</dd>
            <dt>Reference:</dt>
	    <dd><xref target="server_metadata" format="default"/> of [[ this specification ]]</t>
            </list>
          </t> RFC 9701</dd>
          </dl>
        </section>
      </section>
      <section anchor="ietf-media-typeIANA" title="Media numbered="true" toc="default">
        <name>Media Type Registration">
      <t>This section registers the Registration</name>
        <t>The "application/token-introspection+jwt" media type has been registered
	in the "Media Types" registry <xref target="IANA.MediaTypes"/> target="IANA.MediaTypes"
	format="default"/> in the manner described in <xref target="RFC6838"/>, which target="RFC6838"
	format="default"/>. It can be used to indicate that the
	content is a token introspection response in JWT format.</t>
        <section title="Registry Contents">
          <t>
            <list style='symbols'>
              <t>Type name: application</t>
              <t>Subtype name: token-introspection+jwt</t>
   			  <t>Required parameters: N/A</t>
              <t>Optional parameters: N/A</t>
              <t>Encoding considerations: binary; numbered="true" toc="default">
          <name>Registry Contents</name>
          <dl newline="false" spacing="normal">
            <dt>Type name:</dt>
	    <dd>application</dd>
            <dt>Subtype name:</dt>
	    <dd>token-introspection+jwt</dd>
            <dt>Required parameters:</dt>
	    <dd>N/A</dd>
            <dt>Optional parameters:</dt>
	    <dd>N/A</dd>
            <dt>Encoding considerations:</dt>
	    <dd>binary. A token introspection response is a JWT; JWT values are
            encoded as a series of base64url-encoded values (with trailing '='
            characters removed), some of which may be the empty string,
            separated by period ('.') characters.</t>
              <t>Security considerations: See Section 7 characters.</dd>
            <dt>Security considerations:</dt>
	    <dd>see <xref target="Security" format="default"/> of this specification</t>
              <t>Interoperability considerations: N/A</t>
              <t>Published specification: Section 4
	    RFC 9701</dd>
            <dt>Interoperability considerations:</dt>
	    <dd>N/A</dd>
            <dt>Published specification:</dt>
	    <dd><xref target="jwt_request" format="default"/> of this specification</t>
              <t>Applications RFC 9701</dd>
            <dt>Applications that use this media type: Applications type:</dt>
	    <dd>applications that produce and consume
            OAuth Token Introspection Responses in JWT format</t>
              <t>Fragment format</dd>
            <dt>Fragment identifier considerations: N/A</t>
              <t>Additional information:
                 <list style='symbols'>
                   <t>Magic number(s): N/A</t>
                   <t>File extension(s): N/A</t>
                   <t>Macintosh considerations:</dt>
	    <dd>N/A</dd>
	  </dl>
	  <dl newline="true" spacing="normal">
            <dt >Additional information:</dt>
	    <dd>
              <dl newline="false" spacing="compact">
                <dt>Magic number(s):</dt>
		<dd>N/A</dd>
                <dt>File extension(s):</dt>
		<dd>N/A</dd>
                <dt>Macintosh file type code(s): N/A</t>
                 </list>
              </t>
              <t>Person code(s):</dt>
		<dd>N/A</dd>
              </dl>
            </dd>
	  </dl>
	  <dl newline="false" spacing="normal">
            <dt>Person &amp; email address to contact for further information: Torsten Lodderstedt,
                 torsten@lodderstedt.net</t>
              <t>Intended usage: COMMON</t>
              <t>Restrictions information:</dt>
	    <dd><br/>Torsten Lodderstedt (torsten@lodderstedt.net)</dd>
            <dt>Intended usage:</dt>
	    <dd>COMMON</dd>
            <dt>Restrictions on usage: none</t>
              <t>Author: Torsten Lodderstedt, torsten@lodderstedt.net</t>
              <t>Change controller: IESG</t>
              <t>Provisional registration?  No</t>
            </list>
          </t> usage:</dt>
	    <dd>none</dd>
            <dt>Author:</dt>
	    <dd>Torsten Lodderstedt (torsten@lodderstedt.net)</dd>
            <dt>Change controller:</dt>
	    <dd>IETF</dd>
            <dt>Provisional registration?</dt>
	    <dd>No</dd>
          </dl>
        </section>
      </section>
      <section anchor="ietf-jwt-IANA" title="JWT numbered="true" toc="default">
        <name>JWT Claim Registration">
      <t>This section registers the Registration</name>
        <t>The "token_introspection" claim has been registered in the JSON "JSON Web
      Token (JWT) IANA (JWT)" registry <xref target="IANA.JWT"/> target="IANA.JWT" format="default"/> in the manner described in
      <xref target="RFC7519"/>.</t> target="RFC7519" format="default"/>.</t>
        <section title="Registry Contents">
          <t>
            <list style='symbols'>
              <t>Claim name: token_introspection</t>
              <t>Claim description: Token introspection response</t>
              <t>Change Controller: IESG</t>
              <t>Specification Document(s): <xref target="jwt_response"/> of [[this specification]]</t>
            </list>
          </t> numbered="true" toc="default">
          <name>Registry Contents</name>
          <dl newline="false" spacing="compact">
            <dt>Claim Name:</dt>
	    <dd>token_introspection</dd>
            <dt>Claim Description:</dt>
	    <dd>Token introspection response</dd>
            <dt>Change Controller:</dt>
	    <dd>IETF</dd>
            <dt>Reference:</dt>
	    <dd><xref target="jwt_response" format="default"/> of RFC 9701</dd>
          </dl>
        </section>
      </section>
    </section>
  </middle>

  <back>

    <references>
      <name>References</name>
      <references>
        <name>Normative References</name>
        <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/>
        <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6838.xml"/>
        <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7519.xml"/>
        <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9325.xml"/>
        <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7591.xml"/>
        <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7662.xml"/>
        <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7518.xml"/>
        <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7515.xml"/>
        <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7516.xml"/>
        <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/>
        <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8414.xml"/>

<!-- [I-D.ietf-oauth-jwt-bcp] Published as RFC 8725-->
        <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8725.xml"/>

<!--  *****BACK MATTER ***** [I-D.ietf-oauth-security-topics] companion document 9700 -->

  <back>
    <references title="Normative References">
      <?rfc include="reference.RFC.2119"?>
      <?rfc include="reference.RFC.6838"?>
      <?rfc include="reference.RFC.7519"?>
      <?rfc include="reference.RFC.7525"?>
      <?rfc include="reference.RFC.7591"?>
      <?rfc include="reference.RFC.7662"?>
      <?rfc include="reference.RFC.7518"?>
      <?rfc include="reference.RFC.7515"?>
      <?rfc include="reference.RFC.7516"?>
      <?rfc include="reference.RFC.8174"?>
      <?rfc include="reference.RFC.8414"?>
      <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml3/reference.I-D.draft-ietf-oauth-jwt-bcp-06.xml'?>
      <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml3/reference.I-D.draft-ietf-oauth-security-topics-13.xml'?>
<reference anchor="RFC9700" target="https://www.rfc-editor.org/info/rfc9700">
<front>
<title>Best Current Practice for OAuth 2.0 Security</title>
<author initials='T' surname='Lodderstedt' fullname='Torsten Lodderstedt'>
  <organization>yes.com</organization>
</author>
<author initials='J' surname='Bradley' fullname='John Bradley'>
  <organization>Yubico</organization>
</author>
<author initials='A' surname='Labunets' fullname='Andrey Labunets'>
  <organization>Independent Researcher</organization>
</author>
<author initials='D' surname='Fett' fullname='Daniel Fett'>
  <organization>yes.com</organization>
</author>
<date month='December' year='2024'/>
</front>
<seriesInfo name="BCP" value="240"/>
<seriesInfo name="RFC" value="9700"/>
<seriesInfo name="DOI" value="10.17487/RFC9700"/>
</reference>

<reference anchor="OpenID.Registration" target="https://openid.net/specs/openid-connect-registration-1_0.html">
                <front>
            <title>OpenID Connect Dynamic Client Registration 1.0 incorporating errata set 1</title>
            <author fullname="Nat Sakimura">
              <organization>NRI</organization>
            </author>
            <author fullname="John Bradley">
              <organization>Ping Identity</organization>
            </author>
            <author fullname="Mike Jones">
              <organization>Microsoft</organization>
            </author>
            <date day="8" month="Nov" month="November" year="2014"/>
          </front>
        </reference>

        <reference anchor="IANA.MediaTypes" target="http://www.iana.org/assignments/media-types">
          <front>
            <title>Media Types</title>
	  <author fullname="IANA">
	    <organization abbrev="ISO">IANA</organization>
            <author>
              <organization>IANA</organization>
            </author>
            <date/>
          </front>
        </reference>

        <reference anchor="IANA.JWT" target="https://www.iana.org/assignments/jwt/jwt.xhtml#claims"> target="https://www.iana.org/assignments/jwt">
          <front>
            <title>JSON Web Token (JWT) claims registry</title>
	  <author fullname="IANA">
	    <organization abbrev="ISO">IANA</organization> Claims</title>
            <author>
              <organization>IANA</organization>
            </author>
            <date/>
          </front>
        </reference>

        <reference anchor="IANA.OAuth.Token.Introspection" target="https://www.iana.org/assignments/oauth-parameters/oauth-parameters.xhtml#token-introspection-response"> target="https://www.iana.org/assignments/oauth-parameters">
          <front>
            <title>OAuth Token Introspection Response registry</title> Response</title>
            <author>
              <organization>IANA</organization>
            </author>
            <date/>
          </front>
        </reference>
      </references>

    <references title="Informative References">
      <references>
        <name>Informative References</name>

<reference anchor="IANA.OAuth.Parameters" target="http://www.iana.org/assignments/oauth-parameters">
          <front>
            <title>OAuth Parameters</title>
            <author>
              <organization>IANA</organization>
            </author>
            <date/>
          </front>
        </reference>
      </references>
    </references>
        <section anchor="History" title="Document History">
      <t>[[ To be removed from the final specification ]]</t>

     <t>-12<list style="symbols">
          <t>made registration of response parameters intended for cross domain use a MUST (   in RFC 7662)</t>
      </list>
      </t>

      <t>-11<list style="symbols">
          <t>consistent normative language that the AS must authenticate all callers
              to the token introspection endpoint when complying with this specification</t>
          <t>removes text that claims from the JSON Web Token Claims registry may be included
              in the token_introspection claim</t>
          <t>updates the privacy considerations section</t>
          <t>fixes the example BASE64URL encoded JWT payload</t>
      </list>
      </t>

      <t>-10<list style="symbols">
          <t>added requirement to authenticate RS if privacy sensitive data is released</t>
          <t>reworked text on claims from different registries</t>
          <t>added forward reference to privacy considerations to section 5</t>
          <t>added text in privacy considerations regarding client/user tracking</t>
          </list>
      </t>

      <t>-09<list style="symbols">
          <t>changes the Accept and Content-Type HTTP headers from
          "application/json" to "application/token-introspection+jwt" so they
          match the registered media type</t>
          <t>moves the token introspection response members into a JSON object
          claim named "token_introspection" to provide isolation from the top-level
          JWT-specific claims</t>
          <t>"iss", "aud" and "iat" MUST be present as top-level JWT claims</t>
          <t>the "sub" and "exp" claims SHOULD NOT be used as top-level JWT
          claims as additional prevention against JWT access token substitution
          attacks</t>
          </list>
      </t>

	  <t>-08<list style="symbols">
          <t>made difference between introspected access token and
          introspection response clearer</t>
          <t>defined semantics of JWT claims overlapping between
          introspected access token and introspection response as JWT</t>
          <t>added section about RS management</t>
          <t>added text about user claims including a privacy considerations section</t>
          <t>removed registration of OpenID Connect claims to "Token
          Introspection Response" registry and refer to "JWT Claims" registry instead</t>
          <t>added registration of "application/token-introspection+jwt" media type as
          type identifier of token introspection responses in JWT format</t>
          <t>more changed to incorporate IESG review feedback</t>
        </list>
      </t>

	  <t>-07<list style="symbols">
          <t>fixed wrong description of "locale"</t>
          <t>added references for ISO and ITU specifications</t>
        </list>
      </t>

	  <t>-06<list style="symbols">
          <t>replaced reference to RFC 7159 with reference to RFC 8259</t>
        </list>
      </t>

	  <t>-05<list style="symbols">
          <t>improved wording for TLS requirement</t>
          <t>added RFC 2119 boilerplate</t>
          <t>fixed and updated some references</t>
        </list>
      </t>

	  <t>-04<list style="symbols">
          <t>reworked definition of parameters in section 4</t>
          <t>added text on data minimization to security considerations section</t>
          <t>added statement regarding TLS to security considerations section</t>
        </list>
      </t>

	  <t>-03<list style="symbols">
          <t>added registration for OpenID Connect Standard Claims to
          OAuth Token Introspection Response registry</t>
        </list>
      </t>
	  <t>-02<list style="symbols">
          <t>updated references</t>
        </list>
      </t>
	  <t>-01<list style="symbols">
          <t>adapted wording to preclude any accept header except "application/jwt" if
          encrypted responses are required</t>
          <t>use registered alg value RS256 for default signing algorithm</t>
          <t>added text on claims in the token introspection response</t>
        </list>
      </t>
	  <t>-00<list style="symbols">
          <t>initial version of the WG draft</t>
          <t>defined default signing algorithm</t>
          <t>changed behavior in case resource server is set up for encryption</t>
          <t>Added text on token data leakage prevention to the security considerations</t>
          <t>moved Security Considerations section forward</t>
        </list>
      </t>
      <t>WG draft</t>
      <t>-01<list style="symbols">
      	  <t>fixed typos in client meta data field names</t>
      	  <t>added OAuth Server Metadata parameters anchor="Acknowledgements" numbered="false" toc="default">
      <name>Acknowledgements</name>
      <t>We would like to publish algorithms supported
      	  for signing and encrypting the introspection response</t>
      	  <t>added registration of new parameters for OAuth Server Metadata thank <contact fullname="Petteri Stenius"/>, <contact
      fullname="Neil Madden"/>, <contact fullname="Filip Skokan"/>, <contact
      fullname="Tony Nadalin"/>, <contact fullname="Remco Schaar"/>, <contact
      fullname="Justin Richer"/>, <contact fullname="Takahiko Kawasaki"/>, <contact
      fullname="Benjamin Kaduk"/>, <contact fullname=" Robert Wilton"/>, and Client Registration</t>
      	  <t>added explicit request
      <contact fullname="Roman Danyliw"/> for JWT introspection response</t>
      	  <t>made iss and aud claims mandatory in introspection response</t>
      	  <t>Stylistic and clarifying edits, updates references</t>
        </list></t>
      <t>-00<list style="symbols">
          <t>initial version</t>
        </list></t> their valuable feedback.</t>
    </section>
</back> </rfc>