CFRG Elliptic Curve Diffie-Hellman (ECDH) and Signatures in JSON Object Signing and Encryption (JOSE)
RFC 8037

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Internet Engineering Task Force (IETF)                      I. Liusvaara
Request for Comments: 8037                                   Independent
Category: Standards Track                                   January 2017
ISSN: 2070-1721

        CFRG Elliptic Curve Diffie-Hellman (ECDH) and Signatures
              in JSON Object Signing and Encryption (JOSE)

Abstract

   This document defines how to use the Diffie-Hellman algorithms
   "X25519" and "X448" as well as the signature algorithms "Ed25519" and
   "Ed448" from the IRTF CFRG elliptic curves work in JSON Object
   Signing and Encryption (JOSE).

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc8037.

Copyright Notice

   Copyright (c) 2017 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   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.

Liusvaara                    Standards Track                    [Page 1]
RFC 8037            CFRG ECDH and Signatures in JOSE        January 2017

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Key Type "OKP"  . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Algorithms  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Signatures  . . . . . . . . . . . . . . . . . . . . . . .   4
       3.1.1.  Signing . . . . . . . . . . . . . . . . . . . . . . .   4
       3.1.2.  Verification  . . . . . . . . . . . . . . . . . . . .   4
     3.2.  ECDH-ES . . . . . . . . . . . . . . . . . . . . . . . . .   4
       3.2.1.  Performing the ECDH Operation . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .   9
     A.1.  Ed25519 Private Key . . . . . . . . . . . . . . . . . . .   9
     A.2.  Ed25519 Public Key  . . . . . . . . . . . . . . . . . . .   9
     A.3.  JWK Thumbprint Canonicalization . . . . . . . . . . . . .   9
     A.4.  Ed25519 Signing . . . . . . . . . . . . . . . . . . . . .  10
     A.5.  Ed25519 Validation  . . . . . . . . . . . . . . . . . . .  11
     A.6.  ECDH-ES with X25519 . . . . . . . . . . . . . . . . . . .  11
     A.7.  ECDH-ES with X448 . . . . . . . . . . . . . . . . . . . .  12
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  14
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   The Internet Research Task Force (IRTF) Crypto Forum Research Group
   (CFRG) selected new Diffie-Hellman algorithms ("X25519" and "X448";
   [RFC7748]) and signature algorithms ("Ed25519" and "Ed448";
   [RFC8032]) for asymmetric key cryptography.  This document defines
   how to use those algorithms in JOSE in an interoperable manner.

   This document defines the conventions to use in the context of
   [RFC7515], [RFC7516], and [RFC7517].

   While the CFRG also defined two pairs of isogenous elliptic curves
   that underlie these algorithms, these curves are not directly
   exposed, as the algorithms laid on top are sufficient for the
   purposes of JOSE and are much easier to use.

   All inputs to and outputs from the Elliptic Curve Diffie-Hellman
   (ECDH) and signature functions are defined to be octet strings, with
   the exception of outputs of verification functions, which are
   booleans.

Liusvaara                    Standards Track                    [Page 2]
RFC 8037            CFRG ECDH and Signatures in JOSE        January 2017

1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",