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

The information below is for an old version of the document.
Document Type This is an older version of an Internet-Draft whose latest revision is Replaced
Author Yoav Nir
Last updated 2016-04-07
Replaced by draft-ietf-ipsecme-eddsa, draft-ietf-ipsecme-eddsa
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Network Working Group                                             Y. Nir
Internet-Draft                                               Check Point
Intended status: Standards Track                           April 8, 2016
Expires: October 10, 2016

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


   This document describes the use of the Edwards-curve digital
   signature algorithm in the IKEv2 protocol.

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 October 10, 2016.

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
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   ( in effect on the date of
   publication of this document.  Please review these documents
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   described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions Used in This Document . . . . . . . . . . . .   2
   2.  The "Identity" Hash Identifier  . . . . . . . . . . . . . . .   3
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   5.  Normative References  . . . . . . . . . . . . . . . . . . . .   3
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   4

1.  Introduction

   The Internet Key Exchange protocol [RFC7296] can use arbitrary
   signature algorithms as described in [RFC7427].  The latter RFC
   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 before a
   signature phase, which makes sense because most signature algorithms
   either cannot sign messages bigger than their key or truncate
   messages bigger than their key.

   [I.D-eddsa] defines signature algorithms that do not require pre-
   hashing of the message.  Unlike other methods, these signature
   algorithms accept arbitrary-sized messages, so no pre-hashing is
   required.  These methods are called Ed25519 and Ed448, which
   respectively use the Edwards 25519 and the Edwards 448 ("Goldilocks")
   curves.  Although that document also defines pre-hashed versions of
   these algorithm, those versions are not recommended for protocols
   where the entire to-be-signed message is available at once.

   [I.D-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.  [I.D-pkix-newcurves] defined the OIDs for these
   two signature methods.  To signal within IKE that no hashing needs to
   be done.  A new value has to be signalled in the
   SIGNATURE_HASH_ALGORITHMS notification, one that indicates that no
   hashing is performed.

1.1.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

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2.  The "Identity" Hash Identifier

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

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

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

3.  Security Considerations

   The new "Identity" value is needed only for signature algorithms that
   accept an arbitrary-sized input.  It MUST NOT be used if none of the
   supported algorithms has this property.  OTOH there is no good reason
   to hash where the signature algorithm does not require it (or does it
   internally), so the "Identity" value SHOULD be the only one used if
   all of the supported signature algorithms have this property.

4.  IANA Considerations

   IANA is requested to assign a new value from the "IKEv2 Hash
   Algorithms" registry with name "Identity" and this document as

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, <>.

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

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              Josefsson, S. and I. Liusvaara, "Edwards-curve Digital
              Signature Algorithm (EdDSA)", March 2016,

              Josefsson, S., "Using Curve25519 and Curve448 in PKIX",
              March 2016, <

Author's Address

   Yoav Nir
   Check Point Software Technologies Ltd.
   5 Hasolelim st.
   Tel Aviv  6789735


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