< draft-ietf-curdle-ssh-kex-sha2-02.txt		draft-ietf-curdle-ssh-kex-sha2-03.txt >
	Internet Engineering Task Force M. Baushke		Internet Engineering Task Force M. Baushke
	Internet-Draft Juniper Networks, Inc.		Internet-Draft Juniper Networks, Inc.
	Updates: 4253, 4419, 4432, 4462, 5656 March 8, 2016		Updates: 4253, 4419, 4432, 4462, 5656 March 14, 2016
	(if approved)		(if approved)
	Intended status: Standards Track		Intended status: Standards Track
	Expires: September 9, 2016		Expires: September 15, 2016
	Key Exchange Method Updates for Secure Shell (SSH)		Key Exchange (KEX) Method Updates and Recommendations for Secure Shell
	draft-ietf-curdle-ssh-kex-sha2-02		(SSH)
			draft-ietf-curdle-ssh-kex-sha2-03
	Abstract		Abstract
	This document deprecates some previously specified Key Exchange		This document adds recommendations for adoption of ssh-curves from
	Method algorithm names as well as defining a few added Modular		the [I-D.ietf-curdle-ssh-curves], adds some new Modular Exponential
	Exponential (MODP) Groups for the Secure Shell (SSH) protocol. It		(MODP) Groups, and deprecates some previously specified Key Exchange
	also updates [RFC4253], [RFC4419], [RFC4462], and [RFC5656] by		Method algorithm names for the Secure Shell (SSH) protocol. It also
	specifying the set key exchange algorithms that currently exist and		updates [RFC4253], [RFC4419], [RFC4462], and [RFC5656] by specifying
	which ones MUST, SHOULD, MAY, and SHOULD NOT be implemented. New key		the set key exchange algorithms that currently exist and which ones
	exchange methods use the SHA-2 family of hashes.		MUST, SHOULD, MAY, and SHOULD NOT be implemented. New key exchange
			methods use the SHA-2 family of hashes.
	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.
	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 September 9, 2016.		This Internet-Draft will expire on September 15, 2016.
	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 21 ¶		skipping to change at page 2, line 23 ¶
	Secure Shell (SSH) is a common protocol for secure communication on		Secure Shell (SSH) is a common protocol for secure communication on
	the Internet. In [RFC4253], SSH originally defined the Key Exchange		the Internet. In [RFC4253], SSH originally defined the Key Exchange
	Method Name diffie-hellman-group1-sha1 which used [RFC2409] Oakley		Method Name diffie-hellman-group1-sha1 which used [RFC2409] Oakley
	Group 1 (a MODP group with 768 bits) and SHA-1 [RFC3174]. Due to		Group 1 (a MODP group with 768 bits) and SHA-1 [RFC3174]. Due to
	recent security concerns with SHA-1 [RFC6194] and with MODP groups		recent security concerns with SHA-1 [RFC6194] and with MODP groups
	with less than 2048 bits [NIST-SP-800-131Ar1] implementer and users		with less than 2048 bits [NIST-SP-800-131Ar1] implementer and users
	request support for larger MODP group sizes with data integrity		request support for larger MODP group sizes with data integrity
	verification using the SHA-2 family of secure hash algorithms as well		verification using the SHA-2 family of secure hash algorithms as well
	as MODP groups providing more security.		as MODP groups providing more security.
	The United States Information Assurance Directorate at the National		The United States Information Assurance Directorate (IAD) at the
	Security Agency has published a FAQ [MFQ-U-OO-815099-15] suggesting		National Security Agency (NSA) has published a FAQ
	that the use of ECDH using the nistp256 curve and SHA-2 based hashes		[MFQ-U-OO-815099-15] suggesting that the use of Elliptic Curve
			Diffie-Hellman (ECDH) using the nistp256 curve and SHA-2 based hashes
	less than SHA2-384 are no longer sufficient for transport of Top		less than SHA2-384 are no longer sufficient for transport of Top
	Secret information. It is for this reason that this draft moves		Secret information. It is for this reason that this draft moves
	ecdh-sha2-nistp256 from a REQUIRED to OPTIONAL as a key exchange		ecdh-sha2-nistp256 from a REQUIRED to OPTIONAL as a key exchange
	method. This is the same reason that the stronger MODP groups being		method. This is the same reason that the stronger MODP groups being
	introduced are using SHA2-512 as the hash algorithm. Group14 is		introduced are using SHA2-512 as the hash algorithm. Group14 is
	already present in most SSH implementations and most implementations		already present in most SSH implementations and most implementations
	already have a SHA2-256 implementation, so diffie-hellman-		already have a SHA2-256 implementation, so diffie-hellman-
	group14-sha256 is provided as an easy to implement and faster to use		group14-sha256 is provided as an easy to implement and faster to use
	key exchange for small embedded applications.		key exchange for small embedded applications.
	It has been observed in [safe-curves] that the NIST recommended		It has been observed in [safe-curves] that the NIST recommended
	Elliptic Curve Prime Curves (P-256, P-384, and P-521) are perhaps not		Elliptic Curve Prime Curves (P-256, P-384, and P-521) are perhaps not
	the best available for Elliptic Curve Cryptography Security. For		the best available for Elliptic Curve Cryptography (ECC) Security.
	this reason, none of the [RFC5656] curves are marked as a MUST		For this reason, none of the [RFC5656] curves are marked as a MUST
	implement. However, the requirement that "every compliant SSH ECC		implement. However, the requirement that "every compliant SSH ECC
	implementation MUST implement ECDH key exchange" is now taken to mean		implementation MUST implement ECDH key exchange" is now taken to mean
	that if ecdsa-sha2-[identifier] is implemented, then ecdh-		that if ecdsa-sha2-[identifier] is implemented, then ecdh-
	sha2-[identifier] MUST be implemented.		sha2-[identifier] MUST be implemented.
	Please send comments on this draft to ietf-ssh@NetBSD.org.		Please send comments on this draft to curdle@ietf.org.
	2. Requirements Language		2. Requirements Language
	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].
	3. Key Exchange Algorithms		3. Key Exchange Algorithms
	This memo adopts the style and conventions of [RFC4253] in specifying		This memo adopts the style and conventions of [RFC4253] in specifying
	how the use of new data key exchange is indicated in SSH.		how the use of new data key exchange is indicated in SSH.
			A new set of Elliptic Curve Diffie-Hellman ssh-curves exist. The
			curve25519-sha256 MUST be adopted where possible.
			As a hedge against uncertainty raised by the NSA IAD FAQ publication,
			three new MODP Diffie-Hellman based key exchanges are proposed for
			inclusion in the set of key exchange method names as well as the
			curve448-sha512 curve.
	The following new key exchange algorithms are defined:		The following new key exchange algorithms are defined:
	Key Exchange Method Name Note		Key Exchange Method Name Note
	diffie-hellman-group14-sha256 MAY/OPTIONAL		diffie-hellman-group14-sha256 MAY/OPTIONAL
	diffie-hellman-group16-sha512 SHOULD/RECOMMENDED		diffie-hellman-group16-sha512 SHOULD/RECOMMENDED
	diffie-hellman-group18-sha512 MAY/OPTIONAL		diffie-hellman-group18-sha512 MAY/OPTIONAL
	Figure 1		Figure 1
	The SHA-2 family of secure hash algorithms are defined in		The SHA-2 family of secure hash algorithms are defined in
	skipping to change at page 4, line 47 ¶		skipping to change at page 5, line 4 ¶
	SHOULD NOT be used. If it is used, it should only be provided for		SHOULD NOT be used. If it is used, it should only be provided for
	backwards compatibility, should not be used in new designs, and		backwards compatibility, should not be used in new designs, and
	should be phased out of existing key exchanges as quickly as possible		should be phased out of existing key exchanges as quickly as possible
	because of its known weaknesses. Any key exchange using SHA-1 SHOULD		because of its known weaknesses. Any key exchange using SHA-1 SHOULD
	NOT be in a default key exchange list if at all possible. If they		NOT be in a default key exchange list if at all possible. If they
	are needed for backward compatibility, they SHOULD be listed after		are needed for backward compatibility, they SHOULD be listed after
	all of the SHA-2 based key exchanges.		all of the SHA-2 based key exchanges.
	The RFC4253 REQUIRED diffie-hellman-group14-sha1 method SHOULD be		The RFC4253 REQUIRED diffie-hellman-group14-sha1 method SHOULD be
	retained for compatibility with older Secure Shell implementations.		retained for compatibility with older Secure Shell implementations.
	It is intended that this key exchange be phased out as soon as		It is intended that this key exchange be phased out as soon as
	possible.		possible.
	5. Acknowledgements		5. Acknowledgements
	Thanks to the following people for review and comments: Denis Bider,		Thanks to the following people for review and comments: Denis Bider,
	Peter Gutmann, Damien Miller, Niels Moeller, Matt Johnston, Iwamoto		Peter Gutmann, Damien Miller, Niels Moeller, Matt Johnston, Iwamoto
	Kouichi, Simon Josefsson, Dave Dugal.		Kouichi, Simon Josefsson, Dave Dugal, Daniel Migault.
	Thanks to the following people for code to implement interoperable		Thanks to the following people for code to implement interoperable
	exchanges using some of these groups as found in an the -01 draft:		exchanges using some of these groups as found in an this draft:
	Darren Tucker for OpenSSH and Matt Johnston for Dropbear. And thanks		Darren Tucker for OpenSSH and Matt Johnston for Dropbear. And thanks
	to Iwamoto Kouichi for information about RLogin, Tera Term (ttssh)		to Iwamoto Kouichi for information about RLogin, Tera Term (ttssh)
	and Poderosa implementations also adopting new Diffie-Hellman groups		and Poderosa implementations also adopting new Diffie-Hellman groups
	based on the -01 draft.		based on this draft.
	6. Security Considerations		6. Security Considerations
	The security considerations of [RFC4253] apply to this document.		The security considerations of [RFC4253] apply to this document.
	The security considerations of [RFC3526] suggest that these MODP		The security considerations of [RFC3526] suggest that these MODP
	groups have security strengths given in this table. They are based		groups have security strengths given in this table. They are based
	on [RFC3766] Determining Strengths For Public Keys Used For		on [RFC3766] Determining Strengths For Public Keys Used For
	Exchanging Symmetric Keys.		Exchanging Symmetric Keys.
End of changes. 13 change blocks.
	21 lines changed or deleted		33 lines changed or added
This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/