Use of EdDSA Signatures in the Cryptographic Message Syntax (CMS)

The information below is for an old version of the document
Document Type Active Internet-Draft (curdle WG)
Last updated 2016-09-08
Stream IETF
Intended RFC status (None)
Formats pdf htmlized (tools) htmlized bibtex
Stream WG state WG Document
Document shepherd No shepherd assigned
IESG IESG state I-D Exists
Consensus Boilerplate Unknown
Telechat date
Responsible AD (None)
Send notices to (None)
Internet-Draft                                                R. Housley
Intended status: Standards Track                          Vigil Security
Expires: 8 March 2017                                   8 September 2016

   Use of EdDSA Signatures in the Cryptographic Message Syntax (CMS)



   This document describes the conventions for using Edwards-curve
   Digital Signature Algorithm (EdDSA) in the Cryptographic Message
   Syntax (CMS).  The conventions for Ed25519 and Ed448 are described,
   but Ed25519ph and Ed448ph are not used with the CMS.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at

   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 8 March 2017.

Copyright Notice

   Copyright (c) 2016 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
   ( 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.

Housley              Using EdDSA Signatures with CMS            [Page 1]
Internet-Draft                                          8 September 2016

1.  Introduction

   This document specifies the conventions for using the Edwards-curve
   Digital Signature Algorithm (EdDSA) [EDDSA] with the Cryptographic
   Message Syntax [CMS] signed-data content type.  For each curve,
   [EDDSA] defines two modes, the PureEdDSA mode without pre-hashing,
   and the HashEdDSA mode with pre-hashing.  The CMS conventions for two
   PureEdDSA curves (Ed25519 and Ed448) are described in this document,
   but HashEdDSA is not used with the CMS.

1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [STDWORDS].

1.2.  ASN.1

   CMS values are generated using ASN.1 [X680], which uses the Basic
   Encoding Rules (BER) and the Distinguished Encoding Rules (DER)

2.  EdDSA Signature Algorithm

   The Edwards-curve Digital Signature Algorithm (EdDSA) [EDDSA] is a
   variant of Schnorr's signature system with (possibly twisted) Edwards
   curves.  Ed25519 is intended to operate at around the 128-bit
   security level, and Ed448 at around the 224-bit security level.

   One of the parameters of the EdDSA algorithm is the "prehash"
   function.  This may be the identity function, resulting in an
   algorithm called PureEdDSA, or a collision-resistant hash function,
   resulting in an algorithm called HashEdDSA.  In most situations the
   CMS SignedData includes signed attributes, including the message
   digest of the content.  Since HashEdDSA offers no benefit when signed
   attributes are present, only PureEdDSA is used with the CMS.

   A message digest is computed over the data to be signed using
   PureEdDSA, and then a private key operation is performed to generate
   the signature value.  As described in Section 3.3 of [EDDSA], the
   signature value is the opaque value ENC(R) || ENC(S).  As described
   in Section 5.3 of [CMS], the signature value is ASN.1 encoded as an
   OCTET STRING and included in the signature field of SignerInfo.

Housley              Using EdDSA Signatures with CMS            [Page 2]
Internet-Draft                                          8 September 2016

2.1.  EdDSA Algorithm Identifiers

   The EdDSA signature algorithm is defined in [EDDSA], and the
   conventions for encoding the public key are defined in [ID.curdle-

   The id-Ed25519 and id-Ed448 object identifiers are used to identify
   EdDSA public keys in certificates.  The object identifiers are
   specified in [ID.curdle-pkix], and they are repeated here for

      id-Ed25519  OBJECT IDENTIFIER ::= { 1 3 101 112 }
      id-Ed448    OBJECT IDENTIFIER ::= { 1 3 101 113 }

2.2.  EdDSA Signatures

   The id-Ed25519 and id-Ed448 object identifiers are also used for
Show full document text