<?xml version="1.0"encoding="UTF-8"?> <?xml-stylesheet type="text/xsl" href="rfc2629.xslt" ?>encoding="utf-8"?> <!--generatedpre-edited byhttps://github.com/cabo/kramdown-rfc version 1.7.17 (Ruby 3.0.2)ST 09/16/24 --> <!-- formatted by ST 10/07/24 --> <!-- reference review by TH 10/07/24 --> <!DOCTYPE rfc [ <!ENTITY nbsp " "> <!ENTITY zwsp "​"> <!ENTITY nbhy "‑"> <!ENTITY wj "⁠"> ]><?rfc rfcedstyle="yes"?> <?rfc tocindent="yes"?> <?rfc strict="yes"?> <?rfc comments="yes"?> <?rfc inline="yes"?> <?rfc text-list-symbols="-o*+"?> <?rfc docmapping="yes"?><rfc xmlns:xi="http://www.w3.org/2001/XInclude" ipr="trust200902" docName="draft-ietf-cose-key-thumbprint-06" number="9679" updates="" obsoletes="" submissionType="IETF" category="std" consensus="true" tocInclude="true" sortRefs="true"symRefs="true">symRefs="true" version="3" xml:lang="en" > <front> <title abbrev="COSE Key Thumbprint">CBOR Object Signing and Encryption (COSE) Key Thumbprint</title> <seriesInfo name="RFC" value="9679"/> <author initials="K." surname="Isobe" fullname="Kohei Isobe"> <organization>SECOM CO., LTD.</organization> <address> <email>isobekohei@gmail.com</email> </address> </author> <author initials="H." surname="Tschofenig" fullname="Hannes Tschofenig"> <organization abbrev="H-BRS">University of Applied Sciences Bonn-Rhein-Sieg</organization> <address> <postal> <country>Germany</country> </postal> <email>hannes.tschofenig@gmx.net</email> </address> </author> <author initials="O." surname="Steele" fullname="Orie Steele"> <organization>Transmute</organization> <address> <postal> <country>UnitedStates</country>States of America</country> </postal> <email>orie@transmute.industries</email> </address> </author> <date year="2024"month="September" day="06"/> <area>Security</area> <workgroup>COSE</workgroup> <keyword>Internet-Draft</keyword>month="October"/> <area>SEC</area> <workgroup>cose</workgroup> <!-- [rfced] Please insert any keywords (beyond those that appear in the title) for use on https://www.rfc-editor.org/search. --> <abstract><?line 69?><t>This specification defines a method for computing a hash value over a CBOR Object Signing and Encryption (COSE) Key. It specifies which fields within the COSE Key structure are included in the cryptographic hash computation, the process for creating a canonical representation of these fields, and how to hash the resulting byte sequence. The resulting hash value, referred to as a"thumbprint,""thumbprint", can be used to identify or select the corresponding key.</t> </abstract> </front> <middle><?line 78?><sectionanchor="introduction"><name>Introduction</name>anchor="introduction"> <name>Introduction</name> <t>This specification defines a method for applying a cryptographic hash function to a CBOR Object Signing and Encryption (COSE) Key structure <xref target="RFC9052"/>, resulting in a hash value known as a"thumbprint.""thumbprint". To achieve this, the document specifies which fields in the COSE Key structure are included in the hash computation, the process for creating a canonical form of these fields, and how to hash the resulting byte sequence. One of the primary use cases for this thumbprint is as a naming scheme for identifying or selecting the key, such as by using the COSE Key Thumbprint value as a "kid" (key ID). Another key use case involves key derivation functions that use the thumbprints of public keys from the endpoints, along with other application context, to derive a symmetric key.</t> <t>This specification outlines how thumbprints of COSE Keys are generated for both asymmetric and symmetric keys (see Sections <xreftarget="thumbprint"/>target="thumbprint" format="counter"/> and <xreftarget="required"/>).target="required" format="counter"/>). Additionally, it introduces a new CBOR Web Token (CWT) confirmation method, whichishas been added to the IANA "CWT Confirmation Methods" registry established by <xref target="RFC8747"/>. For further details on the use of a confirmation claim in a CWT with a proof-of-possession key, refer toSection 3.1 of<xreftarget="RFC8747"/>.</t>target="RFC8747" sectionFormat="of" section="3.1"/>.</t> </section> <sectionanchor="terminology"><name>Terminology</name> <t>Theanchor="terminology"> <name>Terminology</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 inBCP 14BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and only when, they appear in all capitals, as shownhere.</t>here. </t> </section> <sectionanchor="thumbprint"><name>COSEanchor="thumbprint"> <name>COSE Key Thumbprint</name> <t>The thumbprint of a COSE KeyMUST<bcp14>MUST</bcp14> be computed as follows:</t><t><list style="numbers" type="1"><ol spacing="normal" type="1"><li> <t>Construct a COSE_Key structure (seeSection 7 of<xreftarget="RFC9052"/>)target="RFC9052" sectionFormat="of" section="7"/>) containing only the required parameters representing the key as described inSection 4<xref target="required" format="default"/> of this document.</t> </li> <li> <t>Apply the deterministic encoding described inSection 4.2.1 of<xreftarget="RFC8949"/>target="RFC8949" sectionFormat="of" section="4.2.1"/> to the representation constructed in step(1).</t>1.</t> </li> <li> <t>Hash the bytes produced in step(2)2 with a cryptographic hash function H. For example, SHA-256 <xref target="RFC6234"/> may be used as a hash function.</t></list></t></li> </ol> <t>The details of this computation are further described in subsequent sections.</t> <t>The SHA-256 hash algorithmMUST<bcp14>MUST</bcp14> besupported,supported; other algorithmsMAY<bcp14>MAY</bcp14> be supported.</t> </section> <sectionanchor="required"><name>Requiredanchor="required"> <name>Required COSE Key Parameters</name> <t>Only the required parameters of a key's representation are used when computing its COSE Key Thumbprint value. This section summarizes the required parameters.</t> <t>The "kty" (label: 1) elementMUST<bcp14>MUST</bcp14> be present for all key types, and the integer value specified in the IANACOSE"COSE KeyTypesTypes" registryMUST<bcp14>MUST</bcp14> be used. The tstr data type is not used with thekty"kty" element.</t> <t>Many COSE Key parameters are specific to the chosen key type. The following subsections list the required parameters for commonly used key types.</t> <sectionanchor="octet-key-pair-okp"><name>Octetanchor="octet-key-pair-okp"> <name>Octet Key Pair (OKP)</name> <t>The required parameters for elliptic curve public keys that use theOKPOctet Key Pair (OKP) key type, such as X25519, are:</t><t><list style="symbols"><ul spacing="normal"> <li> <t>"kty" (label: 1, data type: int, value: 1)</t> </li> <li> <t>"crv" (label: -1, value: int)</t> </li> <li> <t>"x" (label: -2, value: bstr)</t></list></t> <t>Details can be found</li> </ul> <t>Further details are described inSection 7.1 of<xreftarget="RFC9053"/>.</t>target="RFC9053" sectionFormat="of" section="7.1"/>.</t> </section> <sectionanchor="ecc"><name>Ellipticanchor="ecc"> <name>Elliptic Curve Keys with X- andY-Coordinate Pair</name>Y-Coordinates</name> <t>The required parameters for elliptic curve public keys that use the EC2 key type, such as NIST P-256, are:</t><t><list style="symbols"><ul spacing="normal"> <li> <t>"kty" (label: 1, data type: int, value: 2)</t> </li> <li> <t>"crv" (label: -1, data type: int)</t> </li> <li> <t>"x" (label: -2, data type: bstr)</t> </li> <li> <t>"y" (label: -3, data type: bstr)</t></list></t> <t>Details can be found</li> </ul> <t>Further details are described inSection 7.1 of<xreftarget="RFC9053"/>.</t>target="RFC9053" sectionFormat="of" section="7.1"/>.</t> <t>Note: <xref target="RFC9052"/> supports both compressed and uncompressed point representations. For interoperability, implementations adhering to this specificationMUST<bcp14>MUST</bcp14> use the uncompressed point representation. Therefore, the y-coordinate is expressed as a bstr. If an implementation uses the compressed point representation, itMUST<bcp14>MUST</bcp14> first convert it to the uncompressed form for the purpose of thumbprint calculation.</t> </section> <sectionanchor="rsa-public-keys"><name>RSAanchor="rsa-public-keys"> <name>RSA Public Keys</name> <t>The required parameters for an RSA public key are:</t><t><list style="symbols"><ul spacing="normal"> <li> <t>"kty" (label: 1, data type: int, value: 3)</t> </li> <li> <t>"n" (label: -1, data type: bstr)</t> </li> <li> <t>"e" (label: -2, data type: bstr)</t></list></t></li> </ul> </section> <sectionanchor="symmetric-keys"><name>Symmetricanchor="symmetric-keys"> <name>Symmetric Keys</name> <t>The required parameters for a symmetric key are:</t><t><list style="symbols"><ul spacing="normal"> <li> <t>"kty" (label: 1, data type: int, value: 4)</t> </li> <li> <t>"k" (label: -1, data type: bstr)</t></list></t></li> </ul> </section> <sectionanchor="hss-lms"><name>HSS-LMS</name>anchor="hss-lms"> <name>HSS-LMS Keys</name> <t>The required parameters for HSS-LMS keys are:</t><t><list style="symbols"><ul spacing="normal"> <li> <t>"kty" (label: 1, data type: int, value: 5)</t> </li> <li> <t>"pub" (label: -1, data type: bstr)</t></list></t></li> </ul> </section> <sectionanchor="others"><name>Others</name>anchor="others"> <name>Others</name> <t>As other key type values are defined,the specificationstheir definingthemspecifications should be similarly consulted to determine which parameters, in addition to the "kty" element, are required.</t> </section> </section> <sectionanchor="miscellaneous-considerations"><name>Miscellaneousanchor="miscellaneous-considerations"> <name>Miscellaneous Considerations</name> <sectionanchor="why-not-include-optional-cose-key-parameters"><name>Whyanchor="why-not-include-optional-cose-key-parameters"> <name>Why Not Include Optional COSE Key Parameters?</name> <t>Optional parameters of COSE Keys are intentionally not included in the COSE Key Thumbprint computation so that their absence or presence in the COSE Key does not alter the resulting value. The COSE Key Thumbprint is a digest of the ordered essential parametersrequiredneeded to representthe key asa COSE Key,rather than any additional data that might accompany the key.</t>with all other parameters excluded.</t> <t>By excluding optional parameters, the COSE Key Thumbprint consistently refers to the key itself, not to a key with additional attributes. Different application contexts may include various optional attributes in the COSE Key structure. If these optional parameters were included in the thumbprint calculation, the resulting values could differ for the same key depending on the attributes present. Including only the required parameters ensures that the COSE Key Thumbprint remains consistent for a given key, regardless of any additional attributes.</t> <t>Different kinds of thumbprints could be defined by other specifications that might include some or all additional COSE Key parameters, if use cases arise where such different kinds of thumbprints would be useful.</t> </section> <sectionanchor="selection-of-hash-function"><name>Selectionanchor="selection-of-hash-function"> <name>Selection of Hash Function</name> <t>A specific hash function must be chosen by an application to compute the hash value of the hash input. For instance, SHA-256 <xref target="RFC6234"/> may be used as the hash function. While SHA-256 is a good default choice at the time of writing, the preferred hash function may evolve as the cryptographic landscape develops.</t> <t>In many cases, only the party that generates the key needs to be aware of the hash function used. For example, the key producer might use the thumbprint value as a "kid" (key ID). In such scenarios, the consumer of the "kid" treats it as an opaque value solely for key selection.</t> <t>However, when multiple parties are involved in reproducing and comparing the COSE Key Thumbprint, it is crucial that they know and use the same hash function to ensure consistent results.</t> </section> <sectionanchor="thumbprints-of-keys-not-in-cose-key-format"><name>Thumbprintsanchor="thumbprints-of-keys-not-in-cose-key-format"> <name>Thumbprints of Keys Not in COSE Key Format</name> <t>Keys that are in other formats can be represented as COSE Keys. Any party in possession of a key that is represented as a COSE Key can use the COSE Key Thumbprint.</t> </section> <sectionanchor="relationship-to-digests-of-x509-values"><name>Relationshipanchor="relationship-to-digests-of-x509-values"> <name>Relationship to Digests of X.509 Values</name> <t>COSE Key Thumbprint values are computed on the COSE Key objectrequired to represent a key, rather than allcontaining only essential parametersofin aCOSE Key that the key is represented in.specific order. Thus, they are more analogous to applications that use digests of X.509 Subject Public Key Info (SPKI) values, which are defined inSection 4.1.2.7 of<xreftarget="RFC5280"/>,target="RFC5280" sectionFormat="of" section="4.1.2.7"/>, than to applications that use digests of complete certificate values, as the "x5t" (X.509 certificate SHA-1 thumbprint) <xref target="RFC9360"/> value defined for X.509 certificate objects does. While logically equivalent to a digest of the SPKI representation of the key, a COSE Key Thumbprint is computed over the CBOR representation of thatkey,key rather than over an ASN.1 representation of it.</t> </section> <sectionanchor="confirmation-method"><name>Confirmationanchor="confirmation-method"> <name>Confirmation Method</name> <t><xref target="RFC8747"/>introducedintroduces confirmation methods for use withCBOR Web Tokens (CWTs)CWTs with the addition of the "cnf" claim. CWTshave beenare defined in <xref target="RFC8392"/>. This specification adds a new confirmation method based on COSE Key Thumbprints.</t> <t>The proof-of-possession key is identified using the "ckt" claim, the COSE Key Thumbprint claim. This claim contains the value of the COSE Key Thumbprint encoded as a binary string. Instead of communicating the actual COSEKeyKey, only the thumbprint is conveyed. This approach assumes that the recipient is able to obtain the identified COSE Key using the thumbprint contained in the "ckt" claim. In this approach, the issuer of a CWT declares that the presenter possesses a particular key and that the recipient can cryptographically confirm the presenter's proof of possession of the key by including a "ckt" claim in the CWT.</t> <t>The following example demonstrates the use of the "ckt" claim in a CWT as part of the confirmation method (withline-breaksline breaks inserted for editorial reasons):</t><figure><artwork><![CDATA[<sourcecode type="cbor-diag"><![CDATA[ { /iss/ 1 : "coaps://as.example.com", /aud/ 3 : "coaps://resource.example.org", /exp/ 4 : 1361398824, /cnf/ 8 : { /ckt/[[TBD1]]5 : h'496bd8afadf307e5b08c64b0421bf9dc 01528a344a43bda88fadd1669da253ec' }} ]]></artwork></figure>}]]></sourcecode> <t><xref target="IANA"/> registers the "ckt" claim and the confirmation method. The "ckt" claim is expected to be used in the "cnf" claim.</t> </section> <sectionanchor="cose-key-thumbprint-uris"><name>COSEanchor="cose-key-thumbprint-uris"> <name>COSE Key Thumbprint URIs</name> <t>This specification defines Uniform Resource Identifiers (URIs) to represent a COSE Key Thumbprint value. The design follows the work oftheJSON Web Key (JWK) Thumbprint URIs, as specified in <xref target="RFC9278"/>. This enables COSE Key Thumbprints to be used, for example, as key identifiers in contexts requiring URIs. This specification defines a URI prefix indicating that the portion of the URI following the prefix is a COSE Key Thumbprint.</t> <t>The following URI prefix is defined to indicate that the portion of the URI following the prefix is a COSE Key Thumbprint:</t><figure><artwork><![CDATA[ urn:ietf:params:oauth:ckt ]]></artwork></figure><t indent="3">urn:ietf:params:oauth:ckt</t> <t>To make the hash algorithm being used explicit in a URI, the prefix is followed by a hash algorithm identifier and a COSE Key Thumbprint value, each separated by a colon character to form a URI representing a COSE Key Thumbprint.</t> <t>Hash algorithm identifiers used in COSE Key Thumbprint URIsMUST<bcp14>MUST</bcp14> be values from the "Hash Name String" column in the IANA "Named Information Hash Algorithm Registry" <xref target="IANA.Hash.Algorithms"/>. COSE Key Thumbprint URIs with hash algorithm identifiers not found in this registry are not consideredvalidvalid, and applicationsMUST<bcp14>MUST</bcp14> detect and handle this error, should it occur.</t> <t>Since the URN is encoded as a string, the output of the COSE Key Thumbprint computation described in <xref target="thumbprint"/>MUST<bcp14>MUST</bcp14> be base64url encoded without padding.</t> <t><xref target="RFC7515"/> specifiesBase64urlbase64url encoding as follows:</t><t>"Base64<!-- [Quote] --> <blockquote>Base64 encoding using the URL- and filename-safe character set defined in Section5<xref target="RFC4648" section="5" sectionFormat="bare"></xref> of RFC 4648 <xref target="RFC4648"/>, with all trailing '=' characters omitted (as permitted by <xref target="RFC7515" sectionFormat="of" section="3.2"/>) and without the inclusion of any line breaks, whitespace, or other additional characters. Note that the base64url encoding of the empty octet sequence is the empty string. (SeeAppendix C of<xreftarget="RFC7515"/>target="RFC7515" sectionFormat="of" section="C"/> for notes on implementing base64url encoding withoutpadding.)"</t>padding.)</blockquote> <!-- [End of quote] --> <t>The base64url encoding of the thumbprint shown in <xref target="example"/> is shown below (with aline-breakline break added for readability purposes).</t><figure><artwork><![CDATA[ SWvYr63zB-WwjGSwQhv53AFSijRKQ72oj63RZp2iU-w ]]></artwork></figure><t indent="3">SWvYr63zB-WwjGSwQhv53AFSijRKQ72oj63RZp2iU-w</t> <t>The full example of a COSE Key Thumbprint URI is shownbelow, again withbelow (with aline-break added.</t> <figure><artwork><![CDATA[ urn:ietf:params:oauth:ckt:sha-256: SWvYr63zB-WwjGSwQhv53AFSijRKQ72oj63RZp2iU-w ]]></artwork></figure>line break added for readability).</t> <t indent="3">urn:ietf:params:oauth:ckt:sha-256:</t> <t indent="3">SWvYr63zB-WwjGSwQhv53AFSijRKQ72oj63RZp2iU-w</t> </section> </section> <sectionanchor="example"><name>Example</name>anchor="example"> <name>Example</name> <t>This section demonstrates the COSE Key Thumbprint computation for the following example COSE Key containing anECCElliptic Curve Cryptography (ECC) public key.</t> <t>For better readability, the example is first presented in CBOR diagnostic format (with the long line broken for display purposes only).</t><figure><artwork><![CDATA[<sourcecode type="cbor-diag"><![CDATA[ { / kty set to EC2 = Elliptic Curve Keys / 1:2, / crv set to P-256 / -1:1, / public key: x-coordinate / -2:h'65eda5a12577c2bae829437fe338701a10aaa375e1bb5b5de108de439c0 8551d', / public key: y-coordinate / -3:h'1e52ed75701163f7f9e40ddf9f341b3dc9ba860af7e0ca7ca7e9eecd008 4d19c', / kid is bstr, not used in COSE Key Thumbprint / 2:h'1decade2facade3'} ]]></artwork></figure>}]]></sourcecode> <t>The example above corresponds to the following CBOR encoding (with link breaks added for display purposes only):</t><figure><artwork><![CDATA[<sourcecode type="test-vectors"><![CDATA[ A50102200121582065EDA5A12577C2BAE829437FE338701A10AAA375E1BB5B5DE108D E439C08551D2258201E52ED75701163F7F9E40DDF9F341B3DC9BA860AF7E0CA7CA7E9 EECD0084D19C0258246D65726961646F632E6272616E64796275636B406275636B6C616E642E6578616D706C65 ]]></artwork></figure>16E642E6578616D706C65]]></sourcecode> <t>Not all of the parameters from the example above are used in the COSE Key Thumbprint computationsincebecause the required parameters of an elliptic curve public key are (as listed in <xref target="ecc"/>) "kty", "crv", "x", and "y".</t> <t>The resulting COSE Key structure, in CBOR diagnostic format withline-breaksline breaks added for better readability, with the minimum parameters in the correct orderare.</t> <figure><artwork><![CDATA[are:</t> <sourcecode type="cbor-diag"><![CDATA[ { 1:2, -1:1, -2:h'65eda5a12577c2bae829437fe338701a 10aaa375e1bb5b5de108de439c08551d', -3:h'1e52ed75701163f7f9e40ddf9f341b3d c9ba860af7e0ca7ca7e9eecd0084d19c'} ]]></artwork></figure>}]]></sourcecode> <t>In CBORencodingencoding, the result is (withline-breaksline breaks added for display purposes only):</t><figure><artwork><![CDATA[<sourcecode type="test-vectors"><![CDATA[ A40102200121582065EDA5A12577C2BAE829437FE338701A10AAA375E1BB5B5DE 108DE439C08551D2258201E52ED75701163F7F9E40DDF9F341B3DC9BA860AF7E0CA7CA7E9EECD0084D19C ]]></artwork></figure>CA7CA7E9EECD0084D19C]]></sourcecode> <t>Using SHA-256, the resulting thumbprint is:</t><figure><artwork><![CDATA[ 496bd8afadf307e5b08c64b0421bf9dc01528a344a43bda88fadd1669da253ec ]]></artwork></figure><sourcecode type="test-vectors"><![CDATA[ 496bd8afadf307e5b08c64b0421bf9dc01528a344a43bda88fadd1669da253ec]]></sourcecode> </section> <sectionanchor="security-considerations"><name>Securityanchor="security-considerations"> <name>Security Considerations</name> <t>A COSE Key Thumbprint will only uniquely identify a particular key if a single unambiguous COSE Key representation for that key is defined and used when computing the COSE Key Thumbprint.</t> <t>A COSE Key Thumbprint will only uniquely identify a particular key if a single unambiguous COSE Key representation for that key is defined and used when computing the COSE Key Thumbprint. Key identifiers are not included in the thumbprint calculation (similarly to other optional parameters in the COSE_Key structure). If the inclusion of specific optional parameters in the thumbprint calculation is important for a particular application, this specification would not be suitable.</t> <t>While thumbprint values are useful for identifying legitimate keys, comparing thumbprint values is not a reliable means of excluding the use of particular keys (or transformations thereof). The reason isthatbecause an attacker may supply a key that is a transformation of a key in orderto havefor itappeartobeappear as a different key. For instance, if a legitimate RSA key uses a modulus value N and an attacker supplies a key with modulus 3*N, the modified key would still work about 1/3 of the time, but it would appear to be a different key.</t> <t>Producing thumbprints of symmetric keys needs to be done with care. DevelopersMUST<bcp14>MUST</bcp14> ensure that the symmetric key has sufficient entropy to prevent attackersto precomputefrom precomputing tables of symmetric keys with their corresponding hash values. This can be prevented if the symmetric key is a randomly selected key of at least128 bita 128-bit length. ThumbprintsMUST NOT<bcp14>MUST NOT</bcp14> be used with passwords or other low-entropy secrets. If a developer is unable to determine whether all symmetric keys used in an application have sufficient entropy, then thumbprints of symmetric keysMUST NOT<bcp14>MUST NOT</bcp14> be used. In general, using thumbprints of symmetric keys should only be used in special applications. In most other deploymentscenariosscenarios, it is more appropriate to utilize a different naming scheme for key identifiers.</t> </section> <sectionanchor="IANA"><name>IANAanchor="IANA"> <name>IANA Considerations</name> <t>IANAis requested to addhas added the following entry to theIANA"CWT Confirmation Methods" registry <xref target="IANA-CWT"/> established by <xref target="RFC8747"/>:</t><t><list style="symbols"> <t>Confirmation<dl spacing="compact" newline="false"> <dt>Confirmation MethodName: ckt</t> <t>ConfirmationName:</dt><dd>ckt</dd> <dt>Confirmation MethodDescription: COSEDescription:</dt><dd>COSE Key SHA-256Thumbprint</t> <t>JWTThumbprint</dd> <dt>JWT Confirmation MethodName: jkt</t> <t>Confirmation Key: [[TBD1]]</t> <t>ConfirmationName:</dt><dd>jkt</dd> <dt>Confirmation Key:</dt><dd>5</dd> <dt>Confirmation ValueType(s): binary string</t> <t>Change Controller: IETF</t> <t>Specification Document(s): [[This document]]</t> </list></t>Type(s):</dt><dd>binary string</dd> <dt>Change Controller:</dt><dd>IETF</dd> <dt>Specification Document(s):</dt><dd>RFC 9679</dd> </dl> <t>Furthermore, IANAis requested to addhas added a value to theIANA"OAuth URI" registry <xref target="IANA-OAuth"/> establishedwithby <xref target="RFC6755"/>:</t><t><list style="symbols"> <t>URN: urn:ietf:params:oauth:ckt</t> <t>Common Name: COSE<dl spacing="compact" newline="false"> <dt>URN:</dt><dd>urn:ietf:params:oauth:ckt</dd> <dt>Common Name:</dt><dd>COSE Key ThumbprintURI</t> <t>Change controller: IETF</t> <t>Specification Document: [[This document]]</t> </list></t>URI</dd> <dt>Change Controller:</dt><dd>IETF</dd> <dt>Specification Document(s):</dt><dd>RFC 9679</dd> </dl> </section> </middle> <back> <references> <name>References</name> <references anchor="sec-normative-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.8949.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.9052.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9053.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8747.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8392.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.4648.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6755.xml"/> </references> <references anchor="sec-informative-references"> <name>Informative References</name> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7638.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6234.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.5280.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9360.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9278.xml"/> <reference anchor="IANA.Hash.Algorithms" target="https://www.iana.org/assignments/named-information"> <front> <title>Named Information Hash Algorithm Registry</title> <author> <organization>IANA</organization> </author> <date/> </front> </reference> <reference anchor="IANA-CWT" target="https://www.iana.org/assignments/cwt"> <front> <title>CWT Confirmation Methods</title> <author> <organization>IANA</organization> </author> <date/> </front> </reference> <reference anchor="IANA-OAuth" target="https://www.iana.org/assignments/oauth-parameters"> <front> <title>OAuth URI</title> <author> <organization>IANA</organization> </author> <date/> </front> </reference> </references> </references> <sectionanchor="acknowledgements"><name>Acknowledgements</name>anchor="acknowledgements" numbered="false"> <name>Acknowledgements</name> <t>We would like to thank the authors of <xref target="RFC7638"/> for their work on theJSON Web Key (JWK)JWK Thumbprint specification. This document applies JWK Thumbprints to COSE Key structures.</t> <t>Additionally, we would like to thankCarsten Bormann, Ilari Liusvaara, Laurence Lundblade, Daisuke Ajitomi, Michael Richardson, Michael<contact fullname="Carsten Bormann"/>, <contact fullname="Ilari Liusvaara"/>, <contact fullname="Laurence Lundblade"/>, <contact fullname="Daisuke Ajitomi"/>, <contact fullname="Michael Richardson"/>, <contact fullname="Michael B.Jones, Mallory Knodel, Joel Jaeggli, Derrell Piper, Patrik Fältström, Warren Kumari, Deb Cooley and Brendan MoranJones"/>, <contact fullname="Mallory Knodel"/>, <contact fullname="Joel Jaeggli"/>, <contact fullname="Derrell Piper"/>, <contact fullname="Patrik Fältström"/>, <contact fullname="Warren Kumari"/>, <contact fullname="Deb Cooley"/>, and <contact fullname="Brendan Moran"/> for their feedback.</t> </section></middle> <back> <references title='Normative References' anchor="sec-normative-references"> <reference anchor="RFC2119"> <front> <title>Key words for use in RFCs to Indicate Requirement Levels</title> <author fullname="S. Bradner" initials="S." surname="Bradner"/> <date month="March" year="1997"/> <abstract> <t>In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.</t> </abstract> </front> <seriesInfo name="BCP" value="14"/> <seriesInfo name="RFC" value="2119"/> <seriesInfo name="DOI" value="10.17487/RFC2119"/> </reference> <reference anchor="RFC8949"> <front> <title>Concise Binary Object Representation (CBOR)</title> <author fullname="C. Bormann" initials="C." surname="Bormann"/> <author fullname="P. Hoffman" initials="P." surname="Hoffman"/> <date month="December" year="2020"/> <abstract> <t>The Concise Binary Object Representation (CBOR) is a data format whose design goals include the possibility of extremely small code size, fairly small message size, and extensibility without the need for version negotiation. These design goals make it different from earlier binary serializations such as ASN.1 and MessagePack.</t> <t>This document obsoletes RFC 7049, providing editorial improvements, new details, and errata fixes while keeping full compatibility with the interchange format of RFC 7049. It does not create a new version of the format.</t> </abstract> </front> <seriesInfo name="STD" value="94"/> <seriesInfo name="RFC" value="8949"/> <seriesInfo name="DOI" value="10.17487/RFC8949"/> </reference> <reference anchor="RFC8174"> <front> <title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</title> <author fullname="B. Leiba" initials="B." surname="Leiba"/> <date month="May" year="2017"/> <abstract> <t>RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.</t> </abstract> </front> <seriesInfo name="BCP" value="14"/> <seriesInfo name="RFC" value="8174"/> <seriesInfo name="DOI" value="10.17487/RFC8174"/> </reference> <reference anchor="RFC9052"> <front> <title>CBOR Object Signing and Encryption (COSE): Structures and Process</title> <author fullname="J. Schaad" initials="J." surname="Schaad"/> <date month="August" year="2022"/> <abstract> <t>Concise Binary Object Representation (CBOR) is a data format designed for small code size and small message size. There is a need to be able to define basic security services for this data format. This document defines the CBOR Object Signing and Encryption (COSE) protocol. This specification describes how to create and process signatures, message authentication codes, and encryption using CBOR for serialization. This specification additionally describes how to represent cryptographic keys using CBOR.</t> <t>This document, along with RFC 9053, obsoletes RFC 8152.</t> </abstract> </front> <seriesInfo name="STD" value="96"/> <seriesInfo name="RFC" value="9052"/> <seriesInfo name="DOI" value="10.17487/RFC9052"/> </reference> <reference anchor="RFC9053"> <front> <title>CBOR Object Signing and Encryption (COSE): Initial Algorithms</title> <author fullname="J. Schaad" initials="J." surname="Schaad"/> <date month="August" year="2022"/> <abstract> <t>Concise Binary Object Representation (CBOR) is a data format designed for small code size and small message size. There is a need to be able to define basic security services for this data format. This document defines a set of algorithms that can be used with the CBOR Object Signing and Encryption (COSE) protocol (RFC 9052).</t> <t>This document, along with RFC 9052, obsoletes RFC 8152.</t> </abstract> </front> <seriesInfo name="RFC" value="9053"/> <seriesInfo name="DOI" value="10.17487/RFC9053"/> </reference> <reference anchor="RFC8747"> <front> <title>Proof-of-Possession Key Semantics for CBOR Web Tokens (CWTs)</title> <author fullname="M. Jones" initials="M." surname="Jones"/> <author fullname="L. Seitz" initials="L." surname="Seitz"/> <author fullname="G. Selander" initials="G." surname="Selander"/> <author fullname="S. Erdtman" initials="S." surname="Erdtman"/> <author fullname="H. Tschofenig" initials="H." surname="Tschofenig"/> <date month="March" year="2020"/> <abstract> <t>This specification describes how to declare in a CBOR Web Token (CWT) (which is defined by RFC 8392) that the presenter of the CWT possesses a particular proof-of-possession key. Being able to prove possession of a key is also sometimes described as being the holder-of-key. This specification provides equivalent functionality to "Proof-of-Possession Key Semantics for JSON Web Tokens (JWTs)" (RFC 7800) but using Concise Binary Object Representation (CBOR) and CWTs rather than JavaScript Object Notation (JSON) and JSON Web Tokens (JWTs).</t> </abstract> </front> <seriesInfo name="RFC" value="8747"/> <seriesInfo name="DOI" value="10.17487/RFC8747"/> </reference> <reference anchor="RFC8392"> <front> <title>CBOR Web Token (CWT)</title> <author fullname="M. Jones" initials="M." surname="Jones"/> <author fullname="E. Wahlstroem" initials="E." surname="Wahlstroem"/> <author fullname="S. Erdtman" initials="S." surname="Erdtman"/> <author fullname="H. Tschofenig" initials="H." surname="Tschofenig"/> <date month="May" year="2018"/> <abstract> <t>CBOR Web Token (CWT) is a compact means of representing claims to be transferred between two parties. The claims in a CWT are encoded in the Concise Binary Object Representation (CBOR), and CBOR Object Signing and Encryption (COSE) is used for added application-layer security protection. A claim is a piece of information asserted about a subject and is represented as a name/value pair consisting of a claim name and a claim value. CWT is derived from JSON Web Token (JWT) but uses CBOR rather than JSON.</t> </abstract> </front> <seriesInfo name="RFC" value="8392"/> <seriesInfo name="DOI" value="10.17487/RFC8392"/> </reference> <reference anchor="RFC7515"> <front> <title>JSON Web Signature (JWS)</title> <author fullname="M. Jones" initials="M." surname="Jones"/> <author fullname="J. Bradley" initials="J." surname="Bradley"/> <author fullname="N. Sakimura" initials="N." surname="Sakimura"/> <date month="May" year="2015"/> <abstract> <t>JSON Web Signature (JWS) represents content secured with digital signatures or Message Authentication Codes (MACs) using JSON-based data structures. Cryptographic algorithms and identifiers for use with this specification are described in the separate JSON Web Algorithms (JWA) specification and an IANA registry defined by that specification. Related encryption capabilities are described in the separate JSON Web Encryption (JWE) specification.</t> </abstract> </front> <seriesInfo name="RFC" value="7515"/> <seriesInfo name="DOI" value="10.17487/RFC7515"/> </reference> <reference anchor="RFC4648"> <front> <title>The Base16, Base32, and Base64 Data Encodings</title> <author fullname="S. Josefsson" initials="S." surname="Josefsson"/> <date month="October" year="2006"/> <abstract> <t>This document describes the commonly used base 64, base 32, and base 16 encoding schemes. It also discusses the use of line-feeds in encoded data, use of padding in encoded data, use of non-alphabet characters in encoded data, use of different encoding alphabets, and canonical encodings. [STANDARDS-TRACK]</t> </abstract> </front> <seriesInfo name="RFC" value="4648"/> <seriesInfo name="DOI" value="10.17487/RFC4648"/> </reference> <reference anchor="RFC6755"> <front> <title>An IETF URN Sub-Namespace for OAuth</title> <author fullname="B. Campbell" initials="B." surname="Campbell"/> <author fullname="H. Tschofenig" initials="H." surname="Tschofenig"/> <date month="October" year="2012"/> <abstract> <t>This document establishes an IETF URN Sub-namespace for use with OAuth-related specifications. This document is not an Internet Standards Track specification; it is published for informational purposes.</t> </abstract> </front> <seriesInfo name="RFC" value="6755"/> <seriesInfo name="DOI" value="10.17487/RFC6755"/> </reference> </references> <references title='Informative References' anchor="sec-informative-references"> <reference anchor="RFC7638"> <front> <title>JSON Web Key (JWK) Thumbprint</title> <author fullname="M. Jones" initials="M." surname="Jones"/> <author fullname="N. Sakimura" initials="N." surname="Sakimura"/> <date month="September" year="2015"/> <abstract> <t>This specification defines a method for computing a hash value over a JSON Web Key (JWK). It defines which fields in a JWK are used in the hash computation, the method of creating a canonical form for those fields, and how to convert the resulting Unicode string into a byte sequence to be hashed. The resulting hash value can be used for identifying or selecting the key represented by the JWK that is the subject of the thumbprint.</t> </abstract> </front> <seriesInfo name="RFC" value="7638"/> <seriesInfo name="DOI" value="10.17487/RFC7638"/> </reference> <reference anchor="RFC6234"> <front> <title>US Secure Hash Algorithms (SHA and SHA-based HMAC and HKDF)</title> <author fullname="D. Eastlake 3rd" initials="D." surname="Eastlake 3rd"/> <author fullname="T. Hansen" initials="T." surname="Hansen"/> <date month="May" year="2011"/> <abstract> <t>Federal Information Processing Standard, FIPS</t> </abstract> </front> <seriesInfo name="RFC" value="6234"/> <seriesInfo name="DOI" value="10.17487/RFC6234"/> </reference> <reference anchor="RFC5280"> <front> <title>Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile</title> <author fullname="D. Cooper" initials="D." surname="Cooper"/> <author fullname="S. Santesson" initials="S." surname="Santesson"/> <author fullname="S. Farrell" initials="S." surname="Farrell"/> <author fullname="S. Boeyen" initials="S." surname="Boeyen"/> <author fullname="R. Housley" initials="R." surname="Housley"/> <author fullname="W. Polk" initials="W." surname="Polk"/> <date month="May" year="2008"/> <abstract> <t>This memo profiles the X.509 v3 certificate and X.509 v2 certificate revocation list (CRL) for use in the Internet. An overview of this approach and model is provided as an introduction. The X.509 v3 certificate format is described in detail, with additional information regarding the format and semantics of Internet name forms. Standard certificate extensions are described and two Internet-specific extensions are defined. A set of required certificate extensions is specified. The X.509 v2 CRL format is described in detail along with standard and Internet-specific extensions. An algorithm for X.509 certification path validation is described. An ASN.1 module and examples are provided in the appendices. [STANDARDS-TRACK]</t> </abstract> </front> <seriesInfo name="RFC" value="5280"/> <seriesInfo name="DOI" value="10.17487/RFC5280"/> </reference> <reference anchor="RFC9360"> <front> <title>CBOR Object Signing and Encryption (COSE): Header Parameters for Carrying and Referencing X.509 Certificates</title> <author fullname="J. Schaad" initials="J." surname="Schaad"/> <date month="February" year="2023"/> <abstract> <t>The CBOR Object Signing and Encryption (COSE) message structure uses references to keys in general. For some algorithms, additional properties are defined that carry parameters relating to keys as needed. The COSE Key structure is used for transporting keys outside of COSE messages. This document extends the way that keys can be identified and transported by providing attributes that refer to or contain X.509 certificates.</t> </abstract> </front> <seriesInfo name="RFC" value="9360"/> <seriesInfo name="DOI" value="10.17487/RFC9360"/> </reference> <reference anchor="RFC9278"> <front> <title>JWK Thumbprint URI</title> <author fullname="M. Jones" initials="M." surname="Jones"/> <author fullname="K. Yasuda" initials="K." surname="Yasuda"/> <date month="August" year="2022"/> <abstract> <t>This specification registers a kind of URI that represents a JSON Web Key (JWK) Thumbprint value. JWK Thumbprints are defined in RFC 7638. 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