draft-ietf-ipsecme-chacha20-poly1305-07.txt		draft-ietf-ipsecme-chacha20-poly1305-08.txt
	Network Working Group Y. Nir		Network Working Group Y. Nir
	Internet-Draft Check Point		Internet-Draft Check Point
	Intended status: Standards Track May 7, 2015		Intended status: Standards Track May 14, 2015
	Expires: November 8, 2015		Expires: November 15, 2015
	ChaCha20, Poly1305 and their use in IKE & IPsec		ChaCha20, Poly1305 and their use in IKE & IPsec
	draft-ietf-ipsecme-chacha20-poly1305-07		draft-ietf-ipsecme-chacha20-poly1305-08
	Abstract		Abstract
	This document describes the use of the ChaCha20 stream cipher along		This document describes the use of the ChaCha20 stream cipher along
	with the Poly1305 authenticator, combined into an AEAD algorithm for		with the Poly1305 authenticator, combined into an AEAD algorithm for
	the Internet Key Exchange protocol (IKEv2) and for IPsec.		the Internet Key Exchange protocol (IKEv2) and for IPsec.
	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
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	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 November 8, 2015.		This Internet-Draft will expire on November 15, 2015.
	Copyright Notice		Copyright Notice
	Copyright (c) 2015 IETF Trust and the persons identified as the		Copyright (c) 2015 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
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	the only other widely supported cipher being the much slower 3DES, it		the only other widely supported cipher being the much slower 3DES, it
	is not feasible to re-configure IPsec installations away from AES.		is not feasible to re-configure IPsec installations away from AES.
	[standby-cipher] describes this issue and the need for a standby		[standby-cipher] describes this issue and the need for a standby
	cipher in greater detail.		cipher in greater detail.
	This document proposes the fast and secure ChaCha20 stream cipher as		This document proposes the fast and secure ChaCha20 stream cipher as
	such a standby cipher in an Authenticated Encryption with Associated		such a standby cipher in an Authenticated Encryption with Associated
	Data (AEAD) construction with the Poly1305 authenticator for use with		Data (AEAD) construction with the Poly1305 authenticator for use with
	the Encapsulated Security Protocol (ESP - [RFC4303]) and the Internet		the Encapsulated Security Protocol (ESP - [RFC4303]) and the Internet
	Key Exchange Protocol (IKEv2 - [RFC7296]). The algorithms are		Key Exchange Protocol (IKEv2 - [RFC7296]). The algorithms are
	described in a separate document ([chacha_poly]). This document only		described in a separate document ([RFC7539]). This document only
	describes the IPsec-specific things.		describes the IPsec-specific things.
	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. ChaCha20 & Poly1305 for ESP		2. ChaCha20 & Poly1305 for ESP
	AEAD_CHACHA20_POLY1305 is a combined mode algorithm, or AEAD. The		AEAD_CHACHA20_POLY1305 is a combined mode algorithm, or AEAD. The
	construction follows the AEAD construction in section 2.8 of		construction follows the AEAD construction in section 2.8 of
	[chacha_poly]:		[RFC7539]:
	o The Initialization Vector (IV) is 64-bit, and is used as part of		o The Initialization Vector (IV) is 64-bit, and is used as part of
	the nonce. The IV MUST be unique for each invocation for a		the nonce. The IV MUST be unique for each invocation for a
	particular SA but does not need to be unpredictable. The use of a		particular SA but does not need to be unpredictable. The use of a
	counter or a linear feedback shift register (LFSR) is RECOMMENDED.		counter or a linear feedback shift register (LFSR) is RECOMMENDED.
	o A 32-bit Salt is prepended to the 64-bit IV to form the 96-bit		o A 32-bit Salt is prepended to the 64-bit IV to form the 96-bit
	nonce. The salt is fixed per SA and it is not transmitted as part		nonce. The salt is fixed per SA and it is not transmitted as part
	of the ESP packet.		of the ESP packet.
	o The encryption key is 256-bit.		o The encryption key is 256-bit.
	o The Internet Key Exchange protocol generates a bitstring called		o The Internet Key Exchange protocol generates a bitstring called
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	plaintext, no padding should be necessary. However, in keeping with		plaintext, no padding should be necessary. However, in keeping with
	the specification in RFC 4303, the plaintext always has a pad length		the specification in RFC 4303, the plaintext always has a pad length
	octet and a Next Header octet and may require padding bytes so as to		octet and a Next Header octet and may require padding bytes so as to
	align the buffer to an integral multiple of 4 octets.		align the buffer to an integral multiple of 4 octets.
	The same key and nonce, along with a block counter of zero are passed		The same key and nonce, along with a block counter of zero are passed
	to the ChaCha20 block function, and the top 256 bits of the result		to the ChaCha20 block function, and the top 256 bits of the result
	are used as the Poly1305 key.		are used as the Poly1305 key.
	Finally, the Poly1305 function is run on the data to be		Finally, the Poly1305 function is run on the data to be
	authenticated, which is, as specified in section 2.8 of [chacha_poly]		authenticated, which is, as specified in section 2.8 of [RFC7539] a
	a concatenation of the following in the below order:		concatenation of the following in the below order:
	o The Authenticated Additional Data (AAD) - see Section 2.1.		o The Authenticated Additional Data (AAD) - see Section 2.1.
	o Zero-octet padding that rounds the length up to 16 bytes. This is		o Zero-octet padding that rounds the length up to 16 bytes. This is
	4 or 8 bytes depending on the length of the AAD.		4 or 8 bytes depending on the length of the AAD.
	o The ciphertext		o The ciphertext
	o Zero octet padding that rounds the total length up to an integral		o Zero octet padding that rounds the total length up to an integral
	multiple of 16 bytes.		multiple of 16 bytes.
	o The length of the additional authenticated data (AAD) in octets		o The length of the additional authenticated data (AAD) in octets
	(as a 64-bit integer encoded in little-endian byte order).		(as a 64-bit integer encoded in little-endian byte order).
	o The length of the ciphertext in octets (as a 64-bit integer		o The length of the ciphertext in octets (as a 64-bit integer
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	The most important security consideration in implementing this draft		The most important security consideration in implementing this draft
	is the uniqueness of the nonce used in ChaCha20. The nonce should be		is the uniqueness of the nonce used in ChaCha20. The nonce should be
	selected uniquely for a particular key, but unpredictability of the		selected uniquely for a particular key, but unpredictability of the
	nonce is not required. Counters and LFSRs are both acceptable ways		nonce is not required. Counters and LFSRs are both acceptable ways
	of generating unique nonces.		of generating unique nonces.
	Another issue with implementing these algorithms is avoiding side		Another issue with implementing these algorithms is avoiding side
	channels. This is trivial for ChaCha20, but requires some care for		channels. This is trivial for ChaCha20, but requires some care for
	Poly1305. Considerations for implementations of these algorithms are		Poly1305. Considerations for implementations of these algorithms are
	in the [chacha_poly] document.		in [RFC7539].
	The Salt value in used nonce construction in ESP and IKEv2 is derived		The Salt value in used nonce construction in ESP and IKEv2 is derived
	from the keystream, same as the encryption key. It is never		from the keystream, same as the encryption key. It is never
	transmitted on the wire, but the security of the algorithm does not		transmitted on the wire, but the security of the algorithm does not
	depend on its secrecy. Thus implementations that keep keys and other		depend on its secrecy. Thus implementations that keep keys and other
	secret material within some security boundary MAY export the Salt		secret material within some security boundary MAY export the Salt
	from the security boundary. This may be useful if the API provided		from the security boundary. This may be useful if the API provided
	by the library accepts the nonce as parameter rather than the IV.		by the library accepts the nonce as parameter rather than the IV.
	6. IANA Considerations		6. IANA Considerations
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	[RFC5282] Black, D. and D. McGrew, "Using Authenticated Encryption		[RFC5282] Black, D. and D. McGrew, "Using Authenticated Encryption
	Algorithms with the Encrypted Payload of the Internet Key		Algorithms with the Encrypted Payload of the Internet Key
	Exchange version 2 (IKEv2) Protocol", RFC 5282, August		Exchange version 2 (IKEv2) Protocol", RFC 5282, August
	2008.		2008.
	[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.
	[chacha_poly]		[RFC7539] Langley, A. and Y. Nir, "ChaCha20 and Poly1305 for IETF
	Langley, A. and Y. Nir, "ChaCha20 and Poly1305 for IETF		protocols", RFC 7539, May 2015.
	protocols", draft-nir-cfrg-chacha20-poly1305-01 (work in
	progress), January 2014.
	8.2. Informative References		8.2. Informative References
	[AE] Bellare, M. and C. Namprempre, "Authenticated Encryption:		[AE] Bellare, M. and C. Namprempre, "Authenticated Encryption:
	Relations among notions and analysis of the generic		Relations among notions and analysis of the generic
	composition paradigm", 2000,		composition paradigm", 2000,
	<http://cseweb.ucsd.edu/~mihir/papers/oem.html>.		<http://cseweb.ucsd.edu/~mihir/papers/oem.html>.
	[FIPS-197]		[FIPS-197]
	National Institute of Standards and Technology, "Advanced		National Institute of Standards and Technology, "Advanced
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