How do you calculate a JWK thumbprint [RFC7638] of these keys?
A thumbprint is supposed to cover the "required" members.
draft-liusvaara-jose-cfrg-curves implies the thumbprint would cover {alg, crv,
kty, x}. That is different from other "kty":"EC" keys, where the thumbprint
covers {crv, kty, x, y}. It is different from all other keys that exclude "alg".
Theoretically we can probably have per-curve thumbprint rules, though so far
the thumbprint rules have been per-type (per kty value).
Two options could be:
1. Reuse "kty":"EC" but have per-curve thumbprint rules
2. Define a new key type, say, "kty":"EC2" for elliptic curve keys with these
thumbprint rules
Either way, draft-liusvaara-jose-cfrg-curves should explicitly state the
members covered by a RFC7638 thumbprint.
--
James Manger
-----Original Message-----
From: jose [mailto:[email protected]] On Behalf Of Ilari Liusvaara
Sent: Wednesday, 11 November 2015 4:56 AM
To: [email protected]
Subject: [jose] CFRG ECC in JOSE
I cooked up a pre-draft (already circulated privately) about using CFRG
ECC work in JOSE. Encompasses both ECDH and signatures.
Comments (before I attempt to submit this as an I-D)?
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Network Working Group I. Liusvaara
Internet-Draft Independent
Intended status: Standards Track October 17, 2015
Expires: April 19, 2016
CFRG curves and signatures in JOSE
draft-liusvaara-jose-cfrg-curves
Abstract
This document defines how to use curves and algorithms from IRTF CFRG
elliptic curves work (Diffie-Hellman and signatures) in JOSE.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts 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 Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 19, 2016.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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publication of this document. Please review these documents
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Terminology . . . . . . . . . . . . . . . . 2
1.2. Notation . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Algorithms . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.1. Signatures . . . . . . . . . . . . . . . . . . . . . . . 3
2.1.1. Curves . . . . . . . . . . . . . . . . . . . . . . . 3
2.1.2. Algorithms . . . . . . . . . . . . . . . . . . . . . 3
2.1.3. Signing . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.4. Verification . . . . . . . . . . . . . . . . . . . . 4
2.2. ECDH-ES . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2.1. Parameters . . . . . . . . . . . . . . . . . . . . . 4
2.2.2. Performing the ECDH operation . . . . . . . . . . . . 5
3. Security considerations . . . . . . . . . . . . . . . . . . . 5
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
5. IANA considerations . . . . . . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.1. Normative References . . . . . . . . . . . . . . . . . . 8
6.2. Informative References . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Internet Research Task Force (IRTF) Crypto Forum Research Group
(CFRG) selected new elliptic curves and signature algorithms for
asymmetric key cryptography. This document defines how those curves
and algorithms are to be used in JOSE in interoperable manner.
This extends [RFC7517] and [RFC7518]
1.1. Requirements Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
1.2. Notation
All inputs to and outputs from the the ECDH and signature functions
are defined to be octet strings, with the exception of output of
verfication function, which is a boolean.
2. Algorithms
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2.1. Signatures
2.1.1. Curves
The following curves are defined for the algorithms are defined here
(to be applied as values of "crv" parameter):
crv value: The curve:
E255 Edwards25519
E448 Edwards448
For each of these curves:
1. The parameter "kty" MUST be "EC".
2. The parameter "crv" MUST be set to appropriate value.
3. The parameter "alg" MUST be set to appropriate value.
4. The parameter "x" is the base64url [RFC4648] encoded public key
octet string (note: this is not the same as sec1 encoding). This
MUST be present for both public and private keys.
5. The parameter "y" MUST NOT be present. These curves only have
one public key component.
6. The parameter "d" is the base64url encoded private key octet
string. This MUST be present for private keys, and MUST NOT be
present for public keys.
7. These curves MUST NOT be used for ECDH-ES.
8. If key is private key, and thus both "x" and "d" are present,
then "x" MUST be the public key corresponding to private key "d".
2.1.2. Algorithms
The following signature algorithms are defined here (to be applied as
values of "alg" parameter):
alg value: crv: The algorithm:
Ed25519 E255 Ed25519
Ed25519ph E255 Ed25519ph
Ed448 E448 Ed448
Ed448ph E448 Ed448ph
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The key type for these algorithms MUST be "EC", "alg" parameter MUST
be present and "crv" parameter MUST match the indicated one for each
algorithm.
2.1.3. Signing
Signing for these is preformed by applying the signing algorithm
defined in [I-D.irtf-cfrg-eddsa] to the private key (as private key),
public key (as public key) and the JWS Signing Input (as message).
The resulting signature is the JWS Signature value. All inputs and
outputs are octet strings.
2.1.4. Verification
Verification is performed by applying the verification algorithm
defined in [I-D.irtf-cfrg-eddsa] to the public key (as public key),
the JWS Signing Input (as message) and the JWS Signature value (as
signature). All inputs are octet strings. If the algorithm accepts,
the signature is valid, otherwise it is invalid.
2.2. ECDH-ES
The following curves are defined for the algorithms are defined here
(to be applied as values of "crv" parameter):
crv value: The curve:
X255 X25519
X448 X448
The key type used with these keys is "EC".
These curves MUST NOT be used for signatures.
2.2.1. Parameters
For each of these curves:
1. The "x" parameter is base64url encoding of point octet string
(note: This is not SEC1 encoding). This parameter MUST be
present in both public and private keys.
2. The "y" parameter MUST NOT be present. These functions only have
one public key component.
3. The "d" parameter is base64url encoding of scalar octet string.
This parameter MUST be present in private keys, and it MUST NOT
be present in public keys.
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4. If key is private key, and thus both "x" and "d" are present,
then "x" MUST be the output of applying ECDH function to the
value of "d" (as scalar input) and the standard basepoint (as
u-coordinate input).
2.2.2. Performing the ECDH operation
The "x" parameter of "epk" field is set as follows:
Apply the appropriate ECDH function to the ephemeral private key (as
scalar input) and the standard basepoint (as u-coordinate input).
The output is the value for "x" parameter of "epk" field. All inputs
and outputs are octet strings.
The Z value (raw key agreement output) for key agreement is
determined as follows:
Apply the appropriate ECDH function to the ephemeral private key (as
scalar input) and receiver public key (as u-coordinate input). The
output is the Z value. All inputs and outputs are octet strings.
3. Security considerations
Security considerations from [I-D.irtf-cfrg-curves] and
[I-D.irtf-cfrg-eddsa] apply here.
The same key MUST NOT be used with multiple algorithms, since some of
the algorithms defined here interact in bad ways. For this reason
"alg" parameters for signature keys are REQUIRED.
Do not assume that signature also binds the key used for signing, it
does not (there are also other widespread signature algorithms where
this binding fails, as such binding is not part of the definition of
secure signature primitive). As an example of such failure, the
Ed25519ph signature of X under key (Ed25519ph,Y) is identical to
Ed25519 signature of SHA512(X) under key (Ed25519,Y). And often it
takes only setting a few bits of message (easy to do by brute force)
to make the message valid enough to be processed in some very
surprising way.
If key generation or batch signature verification is performed, a
well-seed cryptographical random number generator is REQUIRED.
Signing and non-batch signature verification are deterministic
operations do not need random numbers of any kind.
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4. Acknowledgements
Mike Jones for comments on initial pre-draft.
5. IANA considerations
The following is added to JSON Web Signature and Encryption
Algorithms Registry:
o Algorithm Name: "Ed25519"
o Algorithm Description: Ed25519 signature algorithm
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 2.1 of [RFC-THIS]
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "Ed25519ph"
o Algorithm Description: Ed25519 signature algorithm with prehash
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 2.1 of [RFC-THIS]
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "Ed448"
o Algorithm Description: Ed448 signature algorithm
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
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o Specification Document(s): Section 2.1 of [RFC-THIS]
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "Ed448ph"
o Algorithm Description: Ed448 signature algorithm with prehash
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 2.1 of [RFC-THIS]
o Algorithm Analysis Documents(s): n/a
The following is added to JSON Web Key Elliptic Curve Registry:
o Curve Name: "X25519"
o Curve Description: The X25519 function
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 2.2 of [RFC-THIS]
o Curve Name: "X448"
o Curve Description: The X448 function
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 2.2 of [RFC-THIS]
o Curve Name: "Ed25519"
o Curve Description: The Edwards25519 curve
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o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 2.1 of [RFC-THIS]
o Curve Name: "Ed448"
o Curve Description: The Edwards448 curve
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 2.2 of [RFC-THIS]
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<http://www.rfc-editor.org/info/rfc4648>.
[I-D.irtf-cfrg-curves]
Langley, A. and M. Hamburg, "Elliptic Curves for
Security", draft-irtf-cfrg-curves-09 (work in progress),
September 2015.
[I-D.irtf-cfrg-eddsa]
Josefsson, S. and I. Liusvaara, "Edwards-curve Digital
Signature Algorithm (EdDSA)", draft-irtf-cfrg-eddsa-00
(work in progress), October 2015.
6.2. Informative References
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517, DOI 10.17487/
RFC7517, May 2015,
<http://www.rfc-editor.org/info/rfc7517>.
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[RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518, DOI
10.17487/RFC7518, May 2015,
<http://www.rfc-editor.org/info/rfc7518>.
Author's Address
Ilari Liusvaara
Independent
Email: [email protected]
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-Ilari
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