 1/draftietfcosewebauthnalgorithms02.txt 20191101 20:13:09.267032981 0700
+++ 2/draftietfcosewebauthnalgorithms03.txt 20191101 20:13:09.295033686 0700
@@ 1,24 +1,24 @@
COSE Working Group M. Jones
InternetDraft Microsoft
Intended status: Standards Track October 24, 2019
Expires: April 26, 2020
+Intended status: Standards Track November 1, 2019
+Expires: May 4, 2020
COSE and JOSE Registrations for WebAuthn Algorithms
 draftietfcosewebauthnalgorithms02
+ draftietfcosewebauthnalgorithms03
Abstract
The W3C Web Authentication (WebAuthn) specification and the FIDO
 Alliance FIDO2 Client to Authenticator Protocol (CTAP) specification
 use CBOR Object Signing and Encryption (COSE) algorithm identifiers.
+ Alliance Client to Authenticator Protocol (CTAP) specification use
+ CBOR Object Signing and Encryption (COSE) algorithm identifiers.
This specification registers the following algorithms in the IANA
"COSE Algorithms" registry, which are used by WebAuthn and CTAP
implementations: RSASSAPKCS1v1_5 using SHA256, SHA384, SHA512,
and SHA1, and ECDSA using the secp256k1 curve and SHA256. It
registers the secp256k1 elliptic curve in the IANA "COSE Elliptic
Curves" registry. Also, for use with JSON Object Signing and
Encryption (JOSE), it registers the algorithm ECDSA using the
secp256k1 curve and SHA256 in the IANA "JSON Web Signature and
Encryption Algorithms" registry and the secp256k1 elliptic curve in
the IANA "JSON Web Key Elliptic Curve" registry.
@@ 31,83 +31,78 @@
InternetDrafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as InternetDrafts. The list of current Internet
Drafts is at https://datatracker.ietf.org/drafts/current/.
InternetDrafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use InternetDrafts as reference
material or to cite them other than as "work in progress."
 This InternetDraft will expire on April 26, 2020.
+ This InternetDraft will expire on May 4, 2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
InternetDrafCOSE and JOSE Registrations for WebAuthn Algor October 2019

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/licenseinfo) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Notation and Conventions . . . . . . . . . . 3
2. RSASSAPKCS1v1_5 Signature Algorithm . . . . . . . . . . . . 3
3. Using secp256k1 with JOSE and COSE . . . . . . . . . . . . . 4
 3.1. JOSE and COSE secp256k1 Curve Key Representations . . . . 4
+ 3.1. JOSE and COSE secp256k1 Curve Key Representations . . . . 5
3.2. ECDSA Signature with secp256k1 Curve . . . . . . . . . . 5
3.3. Other Uses of the secp256k1 Elliptic Curve . . . . . . . 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
4.1. COSE Algorithms Registrations . . . . . . . . . . . . . . 7
4.2. COSE Elliptic Curves Registrations . . . . . . . . . . . 8
4.3. JOSE Algorithms Registrations . . . . . . . . . . . . . . 8
4.4. JSON Web Key Elliptic Curves Registrations . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5.1. RSA Key Size Security Considerations . . . . . . . . . . 9
5.2. RSASSAPKCS1v1_5 with SHA2 Security Considerations . . 9
5.3. RSASSAPKCS1v1_5 with SHA1 Security Considerations . . 9
5.4. secp256k1 Security Considerations . . . . . . . . . . . . 9
 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
 6.1. Normative References . . . . . . . . . . . . . . . . . . 9
+ 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
+ 6.1. Normative References . . . . . . . . . . . . . . . . . . 10
6.2. Informative References . . . . . . . . . . . . . . . . . 11
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 12
Document History . . . . . . . . . . . . . . . . . . . . . . . . 12
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
This specification defines how to use several algorithms with CBOR
Object Signing and Encryption (COSE) [RFC8152] that are used by
implementations of the W3C Web Authentication (WebAuthn) [WebAuthn]
and FIDO Alliance FIDO2 Client to Authenticator Protocol (CTAP)
[CTAP] specifications. These specification registers these
algorithms in the IANA "COSE Algorithms" registry
 [IANA.COSE.Algorithms] and registers a related elliptic curve in the
 IANA "COSE Elliptic Curves" registry [IANA.COSE.Curves]. This
+ [IANA.COSE.Algorithms] and registers an elliptic curve in the IANA
+ "COSE Elliptic Curves" registry [IANA.COSE.Curves]. This
specification also registers a corresponding algorithm for use with
JSON Object Signing and Encryption (JOSE) [RFC7515] in the IANA "JSON

InternetDrafCOSE and JOSE Registrations for WebAuthn Algor October 2019

Web Signature and Encryption Algorithms" registry
 [IANA.JOSE.Algorithms] and registers a related elliptic curve in the
 IANA "JSON Web Key Elliptic Curve" registry [IANA.JOSE.Curves].
+ [IANA.JOSE.Algorithms] and registers an elliptic curve in the IANA
+ "JSON Web Key Elliptic Curve" registry [IANA.JOSE.Curves].
1.1. Requirements Notation and Conventions
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 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. RSASSAPKCS1v1_5 Signature Algorithm
@@ 116,22 +111,20 @@
The RSASSAPKCS1v1_5 signature algorithm is parameterized with a
hash function (h).
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.
The RSASSAPKCS1v1_5 algorithms specified in this document are in
the following table.
InternetDrafCOSE and JOSE Registrations for WebAuthn Algor October 2019

++++++
 Name  Value  Hash  Description  Recommended 
++++++
 RS256  TBD  SHA256  RSASSAPKCS1v1_5  No 
  (temporary   using SHA256  
  assignment    
  257 already    
  in place)    
 RS384  TBD  SHA384  RSASSAPKCS1v1_5  No 
  (temporary   using SHA384  
@@ 146,20 +139,24 @@
 RS1  TBD  SHA1  RSASSAPKCS1v1_5  Deprecated 
  (temporary   using SHA1  
  assignment    
  65535    
  already in    
  place)    
++++++
Table 1: RSASSAPKCS1v1_5 Algorithm Values
+ Security considerations for use of the first three algorithms are in
+ Section 5.2. Security considerations for use of the last algorithm
+ are in Section 5.3.
+
Note that these algorithms are already present in the IANA "JSON Web
Signature and Encryption Algorithms" registry [IANA.JOSE.Algorithms],
and so these registrations are only for the IANA "COSE Algorithms"
registry [IANA.COSE.Algorithms].
3. Using secp256k1 with JOSE and COSE
This section defines algorithm encodings and representations enabling
the Standards for Efficient Cryptography Group (SECG) elliptic curve
secp256k1 [SEC2] to be used for JOSE [RFC7515] and COSE [RFC8152]
@@ 167,22 +164,20 @@
3.1. JOSE and COSE secp256k1 Curve Key Representations
The Standards for Efficient Cryptography Group (SECG) elliptic curve
secp256k1 [SEC2] is represented in a JSON Web Key (JWK) [RFC7517]
using these values:
o "kty": "EC"
o "crv": "secp256k1"
InternetDrafCOSE and JOSE Registrations for WebAuthn Algor October 2019

plus the values needed to represent the curve point, as defined in
Section 6.2.1 of [RFC7518]. As a compressed point encoding
representation is not defined for JWK elliptic curve points, the
uncompressed point encoding defined there MUST be used. The "x" and
"y" values represented MUST both be exactly 256 bits, with any
leading zeros preserved. Other optional values such as "alg" MAY
also be present.
It is represented in a COSE_Key [RFC8152] using these values:
@@ 215,22 +210,20 @@
1. Generate a digital signature of the JWS Signing Input or the COSE
Sig_structure using ECDSA secp256k1 SHA256 with the desired
private key. The output will be the pair (R, S), where R and S
are 256bit unsigned integers.
2. Turn R and S into octet sequences in bigendian order, with each
array being be 32 octets long. The octet sequence
representations MUST NOT be shortened to omit any leading zero
octets contained in the values.
InternetDrafCOSE and JOSE Registrations for WebAuthn Algor October 2019

3. Concatenate the two octet sequences in the order R and then S.
(Note that many ECDSA implementations will directly produce this
concatenation as their output.)
4. The resulting 64octet sequence is the JWS Signature or COSE
signature value.
Implementations SHOULD use a deterministic algorithm to generate the
ECDSA nonce, k, such as [RFC6979]. However, in situations where
devices are vulnerable to physical attacks, deterministic ECDSA has
@@ 248,38 +241,36 @@
 JOSE Alg  COSE Alg Value  Description  Recommended 
 Name    
+++++
 ES256K  TBD (requested  ECDSA using  Yes 
  assignment 46)  secp256k1 curve and  
   SHA256  
+++++
Table 2: ECDSA Algorithm Values
 Implementation of this algorithm is RECOMMENDED because of its
+ Implementation of this algorithm is recommended because of its
widespread use in decentralized systems and those that chose it over
the NIST curves.
When using a JWK or COSE_Key for this algorithm, the following checks
are made:
o The "kty" field MUST be present and it MUST be "EC" for JOSE or
"EC2" for COSE.
o The "crv" field MUST be present and it MUST represent the
"secp256k1" elliptic curve.
o If the "alg" field is present, it MUST represent the "ES256K"
algorithm.
InternetDrafCOSE and JOSE Registrations for WebAuthn Algor October 2019

o If the "key_ops" field is present, it MUST include "sign" when
creating an ECDSA signature.
o If the "key_ops" field is present, it MUST include "verify" when
verifying an ECDSA signature.
o If the JWK _use_ field is present, its value MUST be "sig".
3.3. Other Uses of the secp256k1 Elliptic Curve
@@ 314,23 +305,20 @@
o Recommended: No
o Name: RS512
o Value: TBD (temporary assignment 259 already in place)
o Description: RSASSAPKCS1v1_5 using SHA512
o Reference: Section 2 of this document
o Recommended: No
o Name: RS1
o Value: TBD (temporary assignment 65535 already in place)

InternetDrafCOSE and JOSE Registrations for WebAuthn Algor October 2019

o Description: RSASSAPKCS1v1_5 using SHA1
o Reference: Section 2 of this document
o Recommended: Deprecated
o Name: ES256K
o Value: TBD (requested assignment 46)
o Description: ECDSA using secp256k1 curve and SHA256
o Reference: Section 3.2 of this document
o Recommended: Yes
@@ 364,22 +352,20 @@
This section registers the following value in the IANA "JSON Web Key
Elliptic Curve" registry [IANA.JOSE.Curves].
o Curve Name: secp256k1
o Curve Description: SECG secp256k1 curve
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.1 of [[ this specification ]]
InternetDrafCOSE and JOSE Registrations for WebAuthn Algor October 2019

5. Security Considerations
5.1. RSA Key Size Security Considerations
The security considerations on key sizes for RSA algorithms from
Section 6.1 of [RFC8230] also apply to the RSA algorithms in this
specification.
5.2. RSASSAPKCS1v1_5 with SHA2 Security Considerations
@@ 414,22 +400,20 @@
6. References
6.1. Normative References
[DSS] National Institute of Standards and Technology (NIST),
"Digital Signature Standard (DSS)", FIPS PUB 1864, July
2013, .
InternetDrafCOSE and JOSE Registrations for WebAuthn Algor October 2019

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
.
[RFC6194] Polk, T., Chen, L., Turner, S., and P. Hoffman, "Security
Considerations for the SHA0 and SHA1 MessageDigest
Algorithms", RFC 6194, DOI 10.17487/RFC6194, March 2011,
.
@@ 464,22 +448,20 @@
[RFC8230] Jones, M., "Using RSA Algorithms with CBOR Object Signing
and Encryption (COSE) Messages", RFC 8230,
DOI 10.17487/RFC8230, September 2017,
.
[SEC1] Standards for Efficient Cryptography Group, "SEC 1:
Elliptic Curve Cryptography", Version 2.0, May 2009,
.
InternetDrafCOSE and JOSE Registrations for WebAuthn Algor October 2019

[SEC2] Standards for Efficient Cryptography Group, "SEC 2:
Recommended Elliptic Curve Domain Parameters",
Version 2.0, January 2010,
.
6.2. Informative References
[CTAP] Brand, C., Czeskis, A., Ehrensvaerd, J., Jones, M., Kumar,
A., Lindemann, R., Powers, A., and J. Verrept, "Client to
Authenticator Protocol (CTAP)", FIDO Alliance Proposed
@@ 513,22 +495,20 @@
IANA, "JSON Web Key Elliptic Curve",
.
[Kudelski17]
Romailler, Y., "How to defeat Ed25519 and EdDSA using
faults", October 2017,
.
InternetDrafCOSE and JOSE Registrations for WebAuthn Algor October 2019

[RFC6979] Pornin, T., "Deterministic Usage of the Digital Signature
Algorithm (DSA) and Elliptic Curve Digital Signature
Algorithm (ECDSA)", RFC 6979, DOI 10.17487/RFC6979, August
2013, .
[WebAuthn]
Balfanz, D., Czeskis, A., Hodges, J., Jones, J., Jones,
M., Kumar, A., Liao, A., Lindemann, R., and E. Lundberg,
"Web Authentication: An API for accessing Public Key
Credentials  Level 1", World Wide Web Consortium
@@ 540,28 +520,31 @@
Thanks to Stephen Farrell, John Fontana, Jeff Hodges, Kevin Jacobs,
J.C. Jones, Benjamin Kaduk, Neil Madden, John Mattsson, Tony
Nadalin, Matt Palmer, Jim Schaad, Goeran Selander, Wendy Seltzer,
Sean Turner, and Samuel Weiler for their roles in registering these
algorithm identifiers.
Document History
[[ to be removed by the RFC Editor before publication as an RFC ]]
+ 03
+
+ o Addressed review of 02 by Jim Schaad.
+
02
o Addressed working group last call comments. Thanks to J.C.
Jones, Kevin Jacobs, Jim Schaad, Neil Madden, and Benjamin Kaduk
for their useful feedback.
01

o Changed the JOSE curve identifier from "P256K" to "secp256k1".
o Specified that secp256k1 signing is done using the SHA256 hash
function.
00
o Created the initial working group draft from draftjonescose
additionalalgorithms00, changing only the title, date, and
history entry.
@@ 559,19 +542,17 @@
o Specified that secp256k1 signing is done using the SHA256 hash
function.
00
o Created the initial working group draft from draftjonescose
additionalalgorithms00, changing only the title, date, and
history entry.
InternetDrafCOSE and JOSE Registrations for WebAuthn Algor October 2019

Author's Address
Michael B. Jones
Microsoft
Email: mbj@microsoft.com
URI: http://selfissued.info/