IPSecME Working Group
Internet Engineering Task Force (IETF)                            Y. Nir
Request for Comments: 8420                                      Dell EMC
Intended status:
Category: Standards Track                        October 26, 2017
Expires: April 29,                                      July 2018
ISSN: 2070-1721

   Using Edwards-curve the Edwards-Curve Digital Signature Algorithm (EdDSA) in the
            Internet Key Exchange Protocol Version 2 (IKEv2)


   This document describes the use of the Edwards-curve digital
   signature algorithm Digital
   Signature Algorithm (EdDSA) in the IKEv2 protocol. Internet Key Exchange Protocol
   Version 2 (IKEv2).

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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   This Internet-Draft will expire on April 29, 2018.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions Used in This Document . . . . . . . . . . . .   3
   2.  The "Identity" Hash Identifier  . . . . . . . . . . . . . . .   3
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   5.  Normative References  . . . . . . . . . . . . . . . . . . . .   3
   Appendix A.  ASN.1 Objects  . . . . . . . . . . . . . . . . . . .   5   4
     A.1.  ASN.1 Object for Ed25519  . . . . . . . . . . . . . . . .   5   4
     A.2.  ASN.1 Object for Ed448  . . . . . . . . . . . . . . . . .   5   4
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   The Internet Key Exchange protocol Protocol Version 2 [RFC7296] can use
   arbitrary signature algorithms as described in [RFC7427].  The latter RFC  [RFC7427]
   defines the SIGNATURE_HASH_ALGORITHMS notification where each side of
   the IKE negotiation lists its supported hash algorithms.  This
   assumes that all signature schemes involve a hashing phase followed
   by a signature phase.  This made sense because most signature
   algorithms either cannot sign messages bigger than their key or
   truncate messages bigger than their key.

   EdDSA ([RFC8032]) [RFC8032] defines signature methods that do not require pre-
   prehashing of the message.  Unlike other methods, these accept
   arbitrary-sized messages,
   messages of arbitrary size, so no pre-hashing prehashing is required.  These
   methods are called Ed25519 and Ed448, which respectively Ed448; they use the Edwards 25519 and
   the Edwards 448 ("Goldilocks") curves. curves, respectively.  Although that
   document also defines pre-hashed prehashed versions of these algorithm, algorithms, those
   versions are not recommended for protocols where the entire to-
   be-signed to-be-
   signed message is available at once. short enough as it is in IKEv2.  See section Section 8.5 or RFC 8032 of
   [RFC8032] for that recommendation.

   EdDSA defines the binary format of the signatures that should be used
   in the "Signature Value" field of the Authentication Data Format in
   section 3.  The CURDLE PKIX document ([I.D-curdle-pkix])
   Section 3 of RFC 8032.  [RFC8410] defines the object identifiers
   (OIDs) for these signature methods.  For convenience, these OIDs are
   repeated in Appendix A.

   In order to signal within IKE that no hashing needs to be done, we
   define a new value in the SIGNATURE_HASH_ALGORITHMS notification, one
   that indicates notification to
   indicate that no hashing is performed.

1.1.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  The "Identity" Hash Identifier

   This document defines a new value called "Identity" (value is 5) (5) in the hash algorithm "IKEv2
   Hash Algorithms" registry for use in the SIGNATURE_HASH_ALGORITHMS
   notification.  Inserting this new value into the notification
   indicates that the receiver supports at least one signature algorithm
   that accepts arbitrary-sized messages of arbitrary size such as Ed25519 and Ed448.

   Ed25519 and Ed448 are only defined with the Identity hash, "Identity" hash and MUST
   NOT be sent to a receiver that has not indicated support for the
   "Identity" hash.

   The pre-hashed prehashed versions of Ed25519 and Ed448 (Ed25519ph and Ed448ph Ed448ph,
   respectively) MUST NOT be used in IKE.

3.  Security Considerations

   The new "Identity" value is needed only for signature algorithms that
   accept an arbitrary-sized input. input of arbitrary size.  It MUST NOT be used if none of
   the supported and configured algorithms have this property.  On the
   hand hand, there is no good reason to pre-hash prehash the inputs where the
   signature algorithm has that property.  For this reason reason,
   implementations MUST have the "Identity" value in the
   SIGNATURE_HASH_ALGORITHMS notification when EdDSA is supported and
   configured.  Implementations SHOULD NOT have other hash algorithms in
   the notification if all supported and configured signature algorithms
   have this property.

4.  IANA Considerations

   IANA has assigned the value 5 for the algorithm with the name
   "Identity" in the "IKEv2 Hash Algorithms" registry with this draft as

   Upon publication of this document IANA is requested to update the
   entry with this document
   as reference.

5.  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,

   [RFC7296]  Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
              Kivinen, "Internet Key Exchange Protocol Version 2
              (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
              2014, <https://www.rfc-editor.org/info/rfc7296>.

   [RFC7427]  Kivinen, T. and J. Snyder, "Signature Authentication in
              the Internet Key Exchange Version 2 (IKEv2)", RFC 7427,
              DOI 10.17487/RFC7427, January 2015,

   [RFC8032]  Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital
              Signature Algorithm (EdDSA)", RFC 8032,
              DOI 10.17487/RFC8032, January 2017,


   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8410]  Josefsson, S. and J. Schaad, "Algorithm Identifiers for
              Ed25519, Ed25519ph, Ed448, Ed448ph, X25519 X25519, and X448 for
              use Use in the Internet
              X.509 Public Key Infrastructure",
              September 2017,
              <https://tools.ietf.org/html/draft-ietf-curdle-pkix-06>. RFC 8410,
              DOI 10.17487/RFC8410, July 2018,

Appendix A.  ASN.1 Objects


   [RFC8410] is the normative reference for the ASN.1 objects for
   Ed25519 and Ed448
   is in [I.D-curdle-pkix]. Ed448.  They are repeated below for convenience.

A.1.  ASN.1 Object for Ed25519

   id-Ed25519 OBJECT IDENTIFIER ::= { }

   Parameters are absent.  Length is 7 bytes.

   Binary encoding: 3005 0603 2B65 70

A.2.  ASN.1 Object for Ed448

   id-Ed448 OBJECT IDENTIFIER ::= { }

   Parameters are absent.  Length is 7 bytes.

   Binary encoding: 3005 0603 2B65 71

Author's Address

   Yoav Nir
   Dell EMC
   9 Andrei Sakharov St
   Haifa  3190500


   Email: ynir.ietf@gmail.com