draft-ietf-ipsecme-safecurves-01.txt		draft-ietf-ipsecme-safecurves-02.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: August 5, 2016 SJD		Expires: February 6, 2017 SJD
	February 2, 2016		August 5, 2016
	Curve25519 and Curve448 for IKEv2 Key Agreement		Curve25519 and Curve448 for IKEv2 Key Agreement
	draft-ietf-ipsecme-safecurves-01		draft-ietf-ipsecme-safecurves-02
	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 August 5, 2016.		This Internet-Draft will expire on February 6, 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 15 ¶		skipping to change at page 2, line 15 ¶
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	1.1. Conventions Used in This Document . . . . . . . . . . . . 2		1.1. Conventions Used in This Document . . . . . . . . . . . . 2
	2. Curve25519 & Curve448 . . . . . . . . . . . . . . . . . . . . 2		2. Curve25519 & Curve448 . . . . . . . . . . . . . . . . . . . . 2
	3. Use and Negotiation in IKEv2 . . . . . . . . . . . . . . . . 3		3. Use and Negotiation in IKEv2 . . . . . . . . . . . . . . . . 3
	3.1. Key Exchange Payload . . . . . . . . . . . . . . . . . . 3		3.1. Key Exchange Payload . . . . . . . . . . . . . . . . . . 3
	3.2. Recipient Tests . . . . . . . . . . . . . . . . . . . . . 4		3.2. Recipient Tests . . . . . . . . . . . . . . . . . . . . . 4
	4. Security Considerations . . . . . . . . . . . . . . . . . . . 4		4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4		5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
	6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4		6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
	7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5		7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
	7.1. Normative References . . . . . . . . . . . . . . . . . . 5		7.1. Normative References . . . . . . . . . . . . . . . . . . 5
	7.2. Informative References . . . . . . . . . . . . . . . . . 5		7.2. Informative References . . . . . . . . . . . . . . . . . 5
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5		Appendix A. Numerical Example for Curve25519 . . . . . . . . . . 5
			Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
	1. Introduction		1. Introduction
	[RFC7748] describes two elliptic curves: Curve25519 and Curve448, as		The "Elliptic Curves for Security" document [RFC7748] describes two
	well as the X25519 and X448 functions for performing key agreement		elliptic curves: Curve25519 and Curve448, as well as the X25519 and
	(Diffie-Hellman) operations with these curves. The curves and		X448 functions for performing key agreement (Diffie-Hellman)
	functions are designed for both performance and security.		operations with these curves. The curves and functions are designed
			for both performance and security.
	Almost ten years ago [RFC4753] specified the first elliptic curve		Almost ten years ago the "ECP Groups for IKE and IKEv2" document
	Diffie-Hellman groups for the Internet Key Exchange protocol (IKEv2 -		[RFC4753] specified the first elliptic curve Diffie-Hellman groups
	[RFC7296]). These were the so-called NIST curves. The state of the		for the Internet Key Exchange protocol (IKEv2 - [RFC7296]). These
	art has advanced since then. More modern curves allow faster		were the so-called NIST curves. The state of the art has advanced
	implementations while making it much easier to write constant-time		since then. More modern curves allow faster implementations while
	implementations free from time-based side-channel attacks. This		making it much easier to write constant-time implementations free
	document defines two such curves for use in IKE. See [Curve25519]		from time-based side-channel attacks. This document defines two such
	for details about the speed and security of the Curve25519 function.		curves for use in IKE. See [Curve25519] for details about the speed
			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 3, line 23 ¶		skipping to change at page 3, line 26 ¶
	SHARED_SECRET = X(d, pub_peer).		SHARED_SECRET = X(d, pub_peer).
	This shared secret is used directly as the value denoted g^ir in		This shared secret is used directly as the value denoted g^ir in
	section 2.14 of RFC 7296. It is 32 octets when Curve25519 is used,		section 2.14 of RFC 7296. It is 32 octets when Curve25519 is used,
	and 56 octets when Curve448 is used.		and 56 octets when Curve448 is used.
	3. Use and Negotiation in IKEv2		3. Use and Negotiation in IKEv2
	The use of Curve25519 and Curve448 in IKEv2 is negotiated using a		The use of Curve25519 and Curve448 in IKEv2 is negotiated using a
	Transform Type 4 (Diffie-Hellman group) in the SA payload of either		Transform Type 4 (Diffie-Hellman group) in the SA payload of either
	an IKE_SA_INIT or a CREATE_CHILD_SA exchange. The value xx is used		an IKE_SA_INIT or a CREATE_CHILD_SA exchange. The value TBA1 is used
	for the group defined by Curve25519 and yy is used for the group		for the group defined by Curve25519 and the value TBA2 is used for
	defined by Curve448. Both are TBA by IANA.		the group defined by Curve448.
	3.1. Key Exchange Payload		3.1. Key Exchange Payload
	The diagram for the Key Exchange Payload from section 3.4 of RFC 7296		The diagram for the Key Exchange Payload from section 3.4 of RFC 7296
	is copied below for convenience:		is copied below for convenience:
	1 2 3		1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Next Payload |C| RESERVED | Payload Length |		| Next Payload |C| RESERVED | Payload Length |
	skipping to change at page 3, line 47 ¶		skipping to change at page 3, line 50 ¶
	| Diffie-Hellman Group Num | RESERVED |		| Diffie-Hellman Group Num | RESERVED |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |		| |
	~ Key Exchange Data ~		~ Key Exchange Data ~
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	o Payload Length - For Curve25519 the public key is 32 octets, so		o Payload Length - For Curve25519 the public key is 32 octets, so
	the Payload Length field will be 40, and for Curve448 the public		the Payload Length field will be 40, and for Curve448 the public
	key is 56 octets, so the Payload Length field will be 64.		key is 56 octets, so the Payload Length field will be 64.
	o The Diffie-Hellman Group Num is xx for Curve25519, or yy for		o The Diffie-Hellman Group Num is TBA1 for Curve25519, or TBA2 for
	Curve448 (both TBA by IANA).		Curve448.
	o The Key Exchange Data is the 32 or 56 octets as described in		o The Key Exchange Data is the 32 or 56 octets as described in
	section 6 of [RFC7748]		section 6 of [RFC7748]
	3.2. Recipient Tests		3.2. Recipient Tests
	This document matches the discussion in [RFC7748] related to		This document matches the discussion in [RFC7748] related to
	receiving and accepting incompatible point formats. In particular,		receiving and accepting incompatible point formats. In particular,
	receiving entities MUST mask the most-significant bit in the final		receiving entities MUST mask the most-significant bit in the final
	byte for X25519 (but not X448), and implementations MUST accept non-		byte for X25519 (but not X448), and implementations MUST accept non-
	canonical values. See section 5 of [RFC7748] for further discussion.		canonical values. See section 5 of [RFC7748] for further discussion.
	skipping to change at page 5, line 7 ¶		skipping to change at page 5, line 12 ¶
	"Curve25519" and "Curve448" and this document as reference. The		"Curve25519" and "Curve448" and this document as reference. The
	Recipient Tests field should also point to this document.		Recipient Tests field should also point to this document.
	6. Acknowledgements		6. Acknowledgements
	Curve25519 was designed by D. J. Bernstein and the parameters for		Curve25519 was designed by D. J. Bernstein and the parameters for
	Curve448 ("Goldilocks") is by Mike Hamburg. The specification of		Curve448 ("Goldilocks") is by Mike Hamburg. The specification of
	algorithms, wire format and other considerations are in RFC 7748 by		algorithms, wire format and other considerations are in RFC 7748 by
	Adam Langley, Mike Hamburg, and Sean Turner.		Adam Langley, Mike Hamburg, and Sean Turner.
			The examples in Appendix A were calculated using the master version
			of OpenSSL, retrieved on August 4th, 2016.
	7. References		7. References
	7.1. Normative References		7.1. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119, March 1997.		Requirement Levels", BCP 14, RFC 2119, March 1997.
	[RFC7296] Kivinen, T., Kaufman, C., Hoffman, P., Nir, Y., and P.		[RFC7296] Kivinen, T., Kaufman, C., Hoffman, P., Nir, Y., and P.
	Eronen, "Internet Key Exchange Protocol Version 2		Eronen, "Internet Key Exchange Protocol Version 2
	(IKEv2)", RFC 7296, October 2014.		(IKEv2)", RFC 7296, October 2014.
	skipping to change at page 5, line 35 ¶		skipping to change at page 5, line 43 ¶
	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",		[RFC4753] Fu, D. and J. Solinas, "ECP Groups For IKE and IKEv2",
	RFC 4753, January 2007.		RFC 4753, January 2007.
	[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.
	Authors' Addresses		Appendix A. Numerical Example for Curve25519
			Suppose we have both the initiator and the responder generating
			private keys by generating 32 random octets. As usual in IKEv2 and
			its extension, we will denote Initiator values with the suffix _i and
			responder values with the suffix _r:
			random_i = 75 1f b4 30 86 55 b4 76 b6 78 9b 73 25 f9 ea 8c
			dd d1 6a 58 53 3f f6 d9 e6 00 09 46 4a 5f 9d 94
			random_r = 0a 54 64 52 53 29 0d 60 dd ad d0 e0 30 ba cd 9e
			55 01 ef dc 22 07 55 a1 e9 78 f1 b8 39 a0 56 88
			These numbers need to be fixed by unsetting some bits as described in
			section 5 of RFC 7748. This affects only the first and last octets
			of each value:
			fixed_i = 70 1f b4 30 86 55 b4 76 b6 78 9b 73 25 f9 ea 8c
			dd d1 6a 58 53 3f f6 d9 e6 00 09 46 4a 5f 9d 54
			fixed_r = 08 54 64 52 53 29 0d 60 dd ad d0 e0 30 ba cd 9e
			55 01 ef dc 22 07 55 a1 e9 78 f1 b8 39 a0 56 48
			The actual private keys are considered to be encoded in little-endian
			format:
			d_i = 549D5F4A460900E6D9F63F53586AD1DD8CEAF925739B78B676B4558630B41F70
			d_r = 4856A039B8F178E9A1550722DCEF01559ECDBA30E0D0ADDD600D295352645408
			The public keys are generated from this using the formula in
			Section 2:
			pub_i = X25519(d_i, G) =
			48 d5 dd d4 06 12 57 ba 16 6f a3 f9 bb db 74 f1
			a4 e8 1c 08 93 84 fa 77 f7 90 70 9f 0d fb c7 66
			pub_r = X25519(d_r, G) =
			0b e7 c1 f5 aa d8 7d 7e 44 86 62 67 32 98 a4 43
			47 8b 85 97 45 17 9e af 56 4c 79 c0 ef 6e ee 25
			And this is the value of the Key Exchange Data field in the key
			exchange payload described in Section 3.1. The shared value is
			calculated as in Section 2:
			SHARED_SECRET = X25519(d_i, pub_r) = X25519(d_r, pub_i) =
			c7 49 50 60 7a 12 32 7f-32 04 d9 4b 68 25 bf b0
			68 b7 f8 31 9a 9e 37 08-ed 3d 43 ce 81 30 c9 50
			Authors' Addresses
	Yoav Nir		Yoav Nir
	Check Point Software Technologies Ltd.		Check Point Software Technologies Ltd.
	5 Hasolelim st.		5 Hasolelim st.
	Tel Aviv 6789735		Tel Aviv 6789735
	Israel		Israel
	Email: ynir.ietf@gmail.com		Email: ynir.ietf@gmail.com
	Simon Josefsson		Simon Josefsson
	SJD AB		SJD AB
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