draft-jones-webauthn-cose-algorithms.xml

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<rfc category="info" 
     ipr="trust200902" 
     docName="draft-jones-webauthn-cose-algorithms-01">
  <front>

    <title>COSE Algorithms for Web Authentication (WebAuthn)</title>

    <author fullname="Michael B. Jones" surname="Jones" initials="M.B.">
      <organization>Microsoft</organization>
      <address>
	<email>mbj@microsoft.com</email>
	<uri>http://self-issued.info/</uri>
      </address>
    </author>

    <date day="2" month="May" year="2018" />

    <area>Security</area>
    <workgroup>WebAuthn Working Group</workgroup>

    <keyword>Cryptography</keyword>
    <keyword>Digital Signature</keyword>
    <keyword>Encryption</keyword>
    <keyword>Internet-Draft</keyword>

    <abstract>
      <t>
	The W3C Web Authentication (WebAuthn) specification uses COSE algorithm identifiers.
	This specification registers algorithms in the IANA "COSE Algorithms" registry
	that are used by WebAuthn that are not already registered.
	Also, they are registered in the IANA "JSON Web Signature and Encryption Algorithms" registry,
	when not already registered there.
      </t>
    </abstract>
  </front>
  <middle>
    <section anchor="Introduction" title="Introduction">
      <t>
	This specification defines how to use several algorithms with
	COSE <xref target="RFC8152"/> that are used by the
	W3C Web Authentication (WebAuthn) <xref target="WebAuthn"/> specification.
	These algorithms are registered in
	the IANA "COSE Algorithms" registry <xref target="IANA.COSE.Algorithms"/>
	and also in
	the IANA "JSON Web Signature and Encryption Algorithms" registry <xref target="IANA.JOSE.Algorithms"/>,
	when not already registered there.
      </t>

      <section anchor="rnc" title="Requirements Notation and Conventions">
        <t>
	  The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	  "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	  "OPTIONAL" in this document are to be interpreted as described in
	  BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and
	  only when, they appear in all capitals, as shown here.
	</t>
      </section>
    </section>

    <section title="RSASSA-PKCS1-v1_5 Signature Algorithm" anchor="RSASSA-PKCS1-v1_5">
      <t>
	The RSASSA-PKCS1-v1_5 signature algorithm is defined in <xref target="RFC8017"/>.
	The RSASSA-PKCS1-v1_5 signature algorithm is parameterized with a hash function (h).
      </t>
      <t>
	A key of size 2048 bits or larger MUST be used with these algorithms.
	Implementations need to check that the key type is 'RSA' when creating or verifying a signature.
      </t>
      <t>
	The RSASSA-PKCS1-v1_5 algorithms specified in this document are in the following table.
      </t>
      <texttable anchor="table-rsa-algs" title="RSASSA-PKCS1-v1_5 Algorithm Values" suppress-title="false" align="center" style="full">
	<ttcol align="left">Name</ttcol>
	<ttcol align="left">Value</ttcol>
	<ttcol align="left">Hash</ttcol>
	<ttcol align="left">Description</ttcol>

	<c>RS256</c>
	<c>TBD (requested assignment -257)</c>
	<c>SHA-256</c>
	<c>RSASSA-PKCS1-v1_5 w/ SHA-256</c>

	<c>RS384</c>
	<c>TBD (requested assignment -258)</c>
	<c>SHA-384</c>
	<c>RSASSA-PKCS1-v1_5 w/ SHA-384</c>

	<c>RS512</c>
	<c>TBD (requested assignment -259)</c>
	<c>SHA-512</c>
	<c>RSASSA-PKCS1-v1_5 w/ SHA-512</c>

	<c>RS1</c>
	<c>TBD (requested assignment -65535)</c>
	<c>SHA-1</c>
	<c>RSASSA-PKCS1-v1_5 w/ SHA-1</c>

      </texttable>
    </section>

    <section anchor="IANA" title="IANA Considerations">

      <section anchor="cose-algorithms-registrations" title="COSE Algorithms Registrations">
        <t>
	  This section registers the following values in the
	  IANA "COSE Algorithms" registry <xref target="IANA.COSE.Algorithms"/>. 
	</t>
	<t>
	  <?rfc subcompact="yes"?>
	  <list style='symbols'>
	    <t>
	      Name: RS256
	    </t>
	    <t>
	      Value: TBD (requested assignment -257)
	    </t>
	    <t>
	      Description: RSASSA-PKCS1-v1_5 w/ SHA-256
	    </t>
	    <t>
	      Reference: <xref target="RSASSA-PKCS1-v1_5"/> of this document 
	    </t>
	    <t>
	      Recommended: No
	    </t>
	  </list>
	</t>
	<t>
	  <list style='symbols'>
	    <t>
	      Name: RS384
	    </t>
	    <t>
	      Value: TBD (requested assignment -258)
	    </t>
	    <t>
	      Description: RSASSA-PKCS1-v1_5 w/ SHA-384
	    </t>
	    <t>
	      Reference: <xref target="RSASSA-PKCS1-v1_5"/> of this document
	    </t>
	    <t>
	      Recommended: No
	    </t>
	  </list>
	</t>
	<t>
	  <list style='symbols'>
	    <t>
	      Name: RS512
	    </t>
	    <t>
	      Value: TBD (requested assignment -259)
	    </t>
	    <t>
	      Description: RSASSA-PKCS1-v1_5 w/ SHA-512
	    </t>
	    <t>
	      Reference: <xref target="RSASSA-PKCS1-v1_5"/> of this document 
	    </t>
	    <t>
	      Recommended: No
	    </t>
	  </list>
	</t>
	<t>
	  <list style='symbols'>
	    <t>
	      Name: RS1
	    </t>
	    <t>
	      Value: TBD (requested assignment -65535)
	    </t>
	    <t>
	      Description: RSASSA-PKCS1-v1_5 w/ SHA-1
	    </t>
	    <t>
	      Reference: <xref target="RSASSA-PKCS1-v1_5"/> of this document 
	    </t>
	    <t>
	      Recommended: Deprecated
	    </t>
	  </list>
	</t>
	<?rfc subcompact="no"?>
      </section>

    </section>

    <section anchor="Security" title="Security Considerations">

      <section title="RSA Key Size Security Considerations" anchor="KeySize-considerations">
	<t>
	  The security considerations on key sizes for RSA algorithms
	  from Section 6.1 of <xref target="RFC8230"/> also apply to the RSA algorithms
	  in this specification.
	</t>
      </section>

      <section title="RSASSA-PKCS1-v1_5 with SHA-2 Security Considerations" anchor="RSASSA-PKCS1-v1_5_SHA-2_considerations">
	<t>
	  The security considerations on the use of RSASSA-PKCS1-v1_5 with SHA-2 hash functions
	  from Section 8.3 of <xref target="RFC7518"/> also apply to their use
	  in this specification.
	  For that reason, these algorithms are registered as being "Not Recommended".
	</t>
      </section>

      <section title="RSASSA-PKCS1-v1_5 with SHA-1 Security Considerations" anchor="RSASSA-PKCS1-v1_5_SHA-1_considerations">
	<t>
	  The security considerations on the use of the SHA-1 hash function
	  from <xref target="RFC6194"/> apply in this specification.
	  For that reason, the "RS1" algorithm is registered as "Deprecated".
	  It MUST NOT be used by COSE implementations.
	</t>
	<t>
	  A COSE algorithm identifier for this algorithm is nonetheless being registered
	  because deployed TPMs continue to use it, and therefore WebAuthn implementations
	  need a COSE algorithm identifier for "RS1" when TPM attestations using
	  this algorithm are being represented.
	</t>
      </section>

    </section>

  </middle>

  <back>
    <references title="Normative References">

      <?rfc include="reference.RFC.2119.xml"?>
      <?rfc include="reference.RFC.6194.xml"?>
      <?rfc include="reference.RFC.7049.xml"?>
      <?rfc include="reference.RFC.7515.xml"?>
      <?rfc include="reference.RFC.7518.xml"?>
      <?rfc include="reference.RFC.8017.xml"?>
      <?rfc include="reference.RFC.8152.xml"?>
      <?rfc include="reference.RFC.8174.xml"?>
      <?rfc include="reference.RFC.8230.xml"?>

    </references>

    <references title="Informative References">

      <reference anchor="WebAuthn" target="https://w3c.github.io/webauthn/">
        <front>
          <title>Web Authentication: An API for accessing Public Key Credentials</title>
          <author initials="D." surname="Balfanz" fullname="Dirk Balfanz">
            <organization>Google</organization>
            <address>
              <email>balfanz@google.com</email>
            </address>
          </author>

          <author initials="A." surname="Czeskis" fullname="Alexei Czeskis">
            <organization>Google</organization>
            <address>
              <email>aczeskis@google.com</email>
            </address>
          </author>

          <author initials="J." surname="Hodges" fullname="Jeff Hodges">
            <organization>PayPal</organization>
            <address>
              <email>Jeff.Hodges@paypal.com</email>
            </address>
          </author>

          <author initials="J.C." surname="Jones" fullname="J.C. Jones">
            <organization>Mozilla</organization>
            <address>
              <email>jc@mozilla.com</email>
            </address>
          </author>

          <author initials="M.B." surname="Jones" fullname="Michael B. Jones">
            <organization>Microsoft</organization>
            <address>
              <email>mbj@microsoft.com</email>
	      <uri>http://self-issued.info/</uri>
            </address>
          </author>

          <author initials="A." surname="Kumar" fullname="Akshay Kumar">
            <organization>Microsoft</organization>
            <address>
              <email>akshayku@microsoft.com</email>
            </address>
          </author>

          <author initials="A." surname="Liao" fullname="Angelo Liao">
            <organization>Microsoft</organization>
            <address>
              <email>huliao@microsoft.com</email>
            </address>
          </author>

          <author initials="R." surname="Lindemann" fullname="Rolf Lindemann">
            <organization>Nok Nok Labs</organization>
            <address>
              <email>rolf@noknok.com</email>
            </address>
          </author>

          <author initials="E." surname="Lundberg" fullname="Emil Lundberg">
            <organization>Yubico</organization>
            <address>
              <email>emil@yubico.com</email>
            </address>
          </author>

          <date month="March" day="20" year="2018" />
        </front>
	<seriesInfo name="" value="Candidate Recommendation" />
        <seriesInfo name="World Wide Web Consortium (W3C)" value="Recommendation-track" />
        <format type="HTML" target="www.w3.org/TR/2018/CR-webauthn-20180320/" />
      </reference>

      <reference anchor="IANA.COSE.Algorithms" target="https://www.iana.org/assignments/cose/cose.xhtml#algorithms">
        <front>
          <title>COSE Algorithms</title>
          <author>
            <organization>IANA</organization>
          </author>
	  <date/>
        </front>
      </reference>

      <reference anchor="IANA.JOSE.Algorithms" target="https://www.iana.org/assignments/jose/jose.xhtml#web-signature-encryption-algorithms">
        <front>
          <title>JSON Web Signature and Encryption Algorithms</title>
          <author>
            <organization>IANA</organization>
          </author>
	  <date/>
        </front>
      </reference>

    </references>

    <section title="Acknowledgements" anchor="Acknowledgements" numbered="no">

      <t>
	Thanks to
	John Fontana,
	Jeff Hodges,
	Tony Nadalin,
	Jim Schaad,
	Göran Selander,
	Wendy Seltzer,
	Sean Turner,
	and
	Samuel Weiler
	for their roles in registering these algorithm identifiers.
      </t>
    </section>

    <section title="Document History" anchor="History">
      <t>
        [[ to be removed by the RFC Editor before publication as an RFC ]]
      </t>

      <t>
        -01
        <list style='symbols'>
          <t>
	    Updated the requested RS1 value from -262 to -65535
	    to match the temporary registration made on 2018-04-19.
          </t>
	  <t>
	    Populated the Acknowledgements section.
	  </t>
        </list>
      </t>

      <t>
        -00
        <list style='symbols'>
          <t>
	    Initial version.
          </t>
        </list>
      </t>

    </section>

  </back>
</rfc>