IPSecME Working Group Y. Nir
Internet-Draft Dell EMC
Intended status: Standards Track October 26, 2017
Expires: April 29, 2018
Using Edwards-curve Digital Signature Algorithm (EdDSA) in the Internet
Key Exchange (IKEv2)
draft-ietf-ipsecme-eddsa-04
Abstract
This document describes the use of the Edwards-curve digital
signature algorithm in the IKEv2 protocol.
Status of This Memo
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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
A.1. ASN.1 Object for Ed25519 . . . . . . . . . . . . . . . . 5
A.2. ASN.1 Object for Ed448 . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
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 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]) defines signature methods that do not require pre-
hashing of the message. Unlike other methods, these 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. See section 8.5 or RFC 8032
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]) 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 that no hashing is performed.
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1.1. Conventions Used in This Document
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].
2. The "Identity" Hash Identifier
This document defines a new value called "Identity" (value is 5) in
the hash algorithm 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 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) 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. It MUST NOT be used if none of the
supported and configured algorithms have this property. On the other
hand there is no good reason to pre-hash the inputs where the
signature algorithm has that property. For this 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
reference.
Upon publication of this document IANA is requested to update the
entry with this document as reference.
5. Normative References
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[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,
<https://www.rfc-editor.org/info/rfc7427>.
[RFC8032] Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital
Signature Algorithm (EdDSA)", RFC 8032,
DOI 10.17487/RFC8032, January 2017,
<https://www.rfc-editor.org/info/rfc8032>.
[I.D-curdle-pkix]
Josefsson, S. and J. Schaad, "Algorithm Identifiers for
Ed25519, Ed25519ph, Ed448, Ed448ph, X25519 and X448 for
use in the Internet X.509 Public Key Infrastructure",
September 2017,
<https://tools.ietf.org/html/draft-ietf-curdle-pkix-06>.
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The normative reference for the ASN.1 objects for Ed25519 and Ed448
is in [I.D-curdle-pkix]. They are repeated below for convenience.
A.1. ASN.1 Object for Ed25519
id-Ed25519 OBJECT IDENTIFIER ::= { 1.3.101.112 }
Parameters are absent. Length is 7 bytes.
Binary encoding: 3005 0603 2B65 70
A.2. ASN.1 Object for Ed448
id-Ed448 OBJECT IDENTIFIER ::= { 1.3.101.113 }
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
Israel
EMail: ynir.ietf@gmail.com
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