< draft-ietf-ipsecme-safecurves-03.txt		draft-ietf-ipsecme-safecurves-04.txt >
	Network Working Group Y. Nir		Network Working Group Y. Nir
	Internet-Draft Check Point		Internet-Draft Check Point
	Intended status: Standards Track S. Josefsson		Intended status: Standards Track S. Josefsson
	Expires: February 10, 2017 SJD		Expires: March 3, 2017 SJD
	August 9, 2016		August 30, 2016
	Curve25519 and Curve448 for IKEv2 Key Agreement		Curve25519 and Curve448 for IKEv2 Key Agreement
	draft-ietf-ipsecme-safecurves-03		draft-ietf-ipsecme-safecurves-04
	Abstract		Abstract
	This document describes the use of Curve25519 and Curve448 for		This document describes the use of Curve25519 and Curve448 for
	ephemeral key exchange in the Internet Key Exchange (IKEv2) protocol.		ephemeral key exchange in the Internet Key Exchange (IKEv2) protocol.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	skipping to change at page 1, line 32 ¶		skipping to change at page 1, line 32 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on February 10, 2017.		This Internet-Draft will expire on March 3, 2017.
	Copyright Notice		Copyright Notice
	Copyright (c) 2016 IETF Trust and the persons identified as the		Copyright (c) 2016 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	skipping to change at page 2, line 30 ¶		skipping to change at page 2, line 30 ¶
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
	1. Introduction		1. Introduction
	The "Elliptic Curves for Security" document [RFC7748] describes two		The "Elliptic Curves for Security" document [RFC7748] describes two
	elliptic curves: Curve25519 and Curve448, as well as the X25519 and		elliptic curves: Curve25519 and Curve448, as well as the X25519 and
	X448 functions for performing key agreement (Diffie-Hellman)		X448 functions for performing key agreement (Diffie-Hellman)
	operations with these curves. The curves and functions are designed		operations with these curves. The curves and functions are designed
	for both performance and security.		for both performance and security.
	Almost ten years ago the "ECP Groups for IKE and IKEv2" document		Elliptic curve Diffie-Hellman [RFC5903] has been specified for the
	[RFC4753] specified the first elliptic curve Diffie-Hellman groups		Internet Key Exchange (IKEv2 - [RFC7296]) for almost ten years. That
	for the Internet Key Exchange protocol (IKEv2 - [RFC7296]). These		document specified the so-called NIST curves. The state of the art
	were the so-called NIST curves. The state of the art has advanced		has advanced since then. More modern curves allow faster
	since then. More modern curves allow faster implementations while		implementations while making it much easier to write constant-time
	making it much easier to write constant-time implementations free		implementations free from time-based side-channel attacks. This
	from time-based side-channel attacks. This document defines two such		document defines two such curves for use in IKE. See [Curve25519]
	curves for use in IKE. See [Curve25519] for details about the speed		for details about the speed and security of the Curve25519 function.
	and security of the Curve25519 function.
	1.1. Conventions Used in This Document		1.1. Conventions Used in This Document
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [RFC2119].		document are to be interpreted as described in [RFC2119].
	2. Curve25519 & Curve448		2. Curve25519 & Curve448
	All cryptographic computations are done using the X25519 and X448		All cryptographic computations are done using the X25519 and X448
	skipping to change at page 4, line 26 ¶		skipping to change at page 4, line 26 ¶
	4. Security Considerations		4. Security Considerations
	Curve25519 and Curve448 are designed to facilitate the production of		Curve25519 and Curve448 are designed to facilitate the production of
	high-performance constant-time implementations. Implementors are		high-performance constant-time implementations. Implementors are
	encouraged to use a constant-time implementation of the functions.		encouraged to use a constant-time implementation of the functions.
	This point is of crucial importance if the implementation chooses to		This point is of crucial importance if the implementation chooses to
	reuse its supposedly ephemeral key pair for many key exchanges, which		reuse its supposedly ephemeral key pair for many key exchanges, which
	some implementations do in order to improve performance.		some implementations do in order to improve performance.
	Curve25519 is intended for the ~128-bit security level, comparable to		Curve25519 is intended for the ~128-bit security level, comparable to
	the 256-bit random ECP group (group 19) defined in RFC 4753, also		the 256-bit random ECP group (group 19) defined in RFC 5903, also
	known as NIST P-256 or secp256r1. Curve448 is intended for the		known as NIST P-256 or secp256r1. Curve448 is intended for the
	~224-bit security level.		~224-bit security level.
	While the NIST curves are advertised as being chosen verifiably at		While the NIST curves are advertised as being chosen verifiably at
	random, there is no explanation for the seeds used to generate them.		random, there is no explanation for the seeds used to generate them.
	In contrast, the process used to pick these curves is fully		In contrast, the process used to pick these curves is fully
	documented and rigid enough so that independent verification has been		documented and rigid enough so that independent verification has been
	done. This is widely seen as a security advantage, since it prevents		done. This is widely seen as a security advantage, since it prevents
	the generating party from maliciously manipulating the parameters.		the generating party from maliciously manipulating the parameters.
	skipping to change at page 5, line 45 ¶		skipping to change at page 5, line 45 ¶
	[RFC7748] Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves		[RFC7748] Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves
	for Security", RFC 7748, January 2016.		for Security", RFC 7748, January 2016.
	7.2. Informative References		7.2. Informative References
	[Curve25519]		[Curve25519]
	Bernstein, J., "Curve25519: New Diffie-Hellman Speed		Bernstein, J., "Curve25519: New Diffie-Hellman Speed
	Records", LNCS 3958, February 2006,		Records", LNCS 3958, February 2006,
	<http://dx.doi.org/10.1007/11745853_14>.		<http://dx.doi.org/10.1007/11745853_14>.
	[RFC4753] Fu, D. and J. Solinas, "ECP Groups For IKE and IKEv2",		[RFC5903] Fu, D. and J. Solinas, "Elliptic Curve Groups modulo a
	RFC 4753, January 2007.		Prime (ECP Groups) for IKE and IKEv2", RFC 5903, June
			2010.
	[RFC6954] Merkle, J. and M. Lochter, "Using the Elliptic Curve		[RFC6954] Merkle, J. and M. Lochter, "Using the Elliptic Curve
	Cryptography (ECC) Brainpool Curves for the Internet Key		Cryptography (ECC) Brainpool Curves for the Internet Key
	Exchange Protocol Version 2 (IKEv2)", RFC 6954, July 2013.		Exchange Protocol Version 2 (IKEv2)", RFC 6954, July 2013.
	Appendix A. Numerical Example for Curve25519		Appendix A. Numerical Example for Curve25519
	Suppose we have both the initiator and the responder generating		Suppose we have both the initiator and the responder generating
	private keys by generating 32 random octets. As usual in IKEv2 and		private keys by generating 32 random octets. As usual in IKEv2 and
	its extension, we will denote Initiator values with the suffix _i and		its extension, we will denote Initiator values with the suffix _i and
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