< draft-ietf-tls-ciphersuite-05.txt		draft-ietf-tls-ciphersuite-06.txt >
			A new Request for Comments is now available in online RFC libraries.
	Network Working Group Pete Chown		RFC 3268
	INTERNET DRAFT Skygate Technology
	<draft-ietf-tls-ciphersuite-05.txt> 14 August 2001
	AES Ciphersuites for TLS
	Status of this Memo
	This document is an Internet-Draft and is in full conformance with
	all provisions of Section 10 of RFC2026.
	Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF), its areas, and its working groups. Note that
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	Distribution of this document is unlimited. Please send comments to
	the author (pc@skygate.co.uk) or to the Transport Layer Security
	Working Group's discussion list (ietf-tls@lists.certicom.com).
	Overview
	At present, the symmetric ciphers supported by TLS are RC2, RC4,
	IDEA, DES and triple DES. The protocol would be enhanced by the
	addition of AES [AES] ciphersuites, for the following reasons:
	1. RC2, RC4 and IDEA are all subject to intellectual property
	claims. RSA Security Inc has trademark rights in the names RC2
	and RC4, and claims that the RC4 algorithm itself is a trade
	secret. Ascom Systec Ltd owns a patent on the IDEA algorithm.
	2. Triple DES is much less efficient than more modern ciphers.
	3. Now the AES process is completed there will be commercial pres¡
	sure to use the selected cipher. The AES is efficient and has
	withstood extensive cryptanalytic efforts. The AES is
	ietf-tls-ciphersuite-05 AES Ciphersuites for TLS 14 August 2001
	therefore a desirable choice.
	4. Currently the DHE ciphersuites only allow triple DES (along
	with some ``export'' variants which do not use a satisfactory
	key length). At the same time the DHE ciphersuites are the
	only ones to offer forward secrecy.
	This document proposes several new ciphersuites, with the aim of
	overcoming these problems.
	Cipher Usage
	The new ciphersuites proposed here are very similar to the follow¡
	ing, defined in [TLS]:
	TLS_RSA_WITH_3DES_EDE_CBC_SHA
	TLS_DH_DSS_WITH_3DES_EDE_CBC_SHA
	TLS_DH_RSA_WITH_3DES_EDE_CBC_SHA
	TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA
	TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA
	TLS_DH_anon_WITH_3DES_EDE_CBC_SHA
	All the ciphersuites described here use the AES in cipher block
	chaining (CBC) mode. Furthermore, they use SHA-1 [SHA-1] in an
	HMAC construction as described in section 5 of [TLS]. (Although
	the TLS ciphersuite names include the text ``SHA'', this actually
	refers to the modified SHA-1 version of the algorithm.)
	The ciphersuites differ in the type of certificate and key exchange
	method. The ciphersuites defined here use the following options
	for this part of the protocol:
	ietf-tls-ciphersuite-05 AES Ciphersuites for TLS 14 August 2001
	CipherSuite Certificate type (if applicable)
	and key exchange algorithm
	TLS_RSA_WITH_AES_128_CBC_SHA RSA
	TLS_DH_DSS_WITH_AES_128_CBC_SHA DH_DSS
	TLS_DH_RSA_WITH_AES_128_CBC_SHA DH_RSA
	TLS_DHE_DSS_WITH_AES_128_CBC_SHA DHE_DSS
	TLS_DHE_RSA_WITH_AES_128_CBC_SHA DHE_RSA
	TLS_DH_anon_WITH_AES_128_CBC_SHA DH_anon
	TLS_RSA_WITH_AES_256_CBC_SHA RSA
	TLS_DH_DSS_WITH_AES_256_CBC_SHA DH_DSS
	TLS_DH_RSA_WITH_AES_256_CBC_SHA DH_RSA
	TLS_DHE_DSS_WITH_AES_256_CBC_SHA DHE_DSS
	TLS_DHE_RSA_WITH_AES_256_CBC_SHA DHE_RSA
	TLS_DH_anon_WITH_AES_256_CBC_SHA DH_anon
	For the meanings of the terms RSA, DH_DSS, DH_RSA, DHE_DSS, DHE_RSA
	and DH_anon, please refer to sections 7.4.2 and 7.4.3 of [TLS].
	The AES supports key lengths of 128, 192 and 256 bits. However,
	this document only defines ciphersuites for 128- and 256-bit keys.
	This is to avoid unnecessary proliferation of ciphersuites. Rijn¡
	dael actually allows for 192- and 256-bit block sizes as well as
	the 128-bit blocks mandated by the AES process. The ciphersuites
	defined here all use 128-bit blocks.
	The new ciphersuites will have the following definitions:
	CipherSuite TLS_RSA_WITH_AES_128_CBC_SHA = { 0x00, 0x2F };
	CipherSuite TLS_DH_DSS_WITH_AES_128_CBC_SHA = { 0x00, 0x30 };
	CipherSuite TLS_DH_RSA_WITH_AES_128_CBC_SHA = { 0x00, 0x31 };
	CipherSuite TLS_DHE_DSS_WITH_AES_128_CBC_SHA = { 0x00, 0x32 };
	CipherSuite TLS_DHE_RSA_WITH_AES_128_CBC_SHA = { 0x00, 0x33 };
	CipherSuite TLS_DH_anon_WITH_AES_128_CBC_SHA = { 0x00, 0x34 };
	CipherSuite TLS_RSA_WITH_AES_256_CBC_SHA = { 0x00, 0x35 };
	CipherSuite TLS_DH_DSS_WITH_AES_256_CBC_SHA = { 0x00, 0x36 };
	CipherSuite TLS_DH_RSA_WITH_AES_256_CBC_SHA = { 0x00, 0x37 };
	CipherSuite TLS_DHE_DSS_WITH_AES_256_CBC_SHA = { 0x00, 0x38 };
	CipherSuite TLS_DHE_RSA_WITH_AES_256_CBC_SHA = { 0x00, 0x39 };
	CipherSuite TLS_DH_anon_WITH_AES_256_CBC_SHA = { 0x00, 0x3A };
	Security Considerations
	It is not believed that the new ciphersuites are ever less secure
	than the corresponding older ones. The AES is believed to be
	ietf-tls-ciphersuite-05 AES Ciphersuites for TLS 14 August 2001
	secure, and it has withstood extensive cryptanalytic attack.
	The ephemeral Diffie-Hellman ciphersuites provide forward secrecy
	without any known reduction in security in other areas. To obtain
	the maximum benefit from these ciphersuites:
	1. The ephemeral keys should only be used once. With the TLS pro¡
	tocol as currently defined there is no significant efficiency
	gain from reusing ephemeral keys.
	2. Ephemeral keys should be destroyed securely when they are no
	longer required.
	3. The random number generator used to create ephemeral keys must
	not reveal past output even when its internal state is compro¡
	mised.
	[TLS] describes the anonymous Diffie-Hellman (ADH) ciphersuites as
	deprecated. The ADH ciphersuites defined here are not deprecated.
	However, when they are used, particular care must be taken:
	1. ADH provides confidentiality but not authentication. This
	means that (if authentication is required) the communicating
	parties must authenticate to each other by some means other
	than TLS.
	2. ADH is vulnerable to man-in-the-middle attacks, as a conse¡
	quence of the lack of authentication. The parties must have a
	way of determining whether they are participating in the same
	TLS connection. If they are not, they can deduce that they are
	under attack, and presumably abort the connection.
	For example, if the parties share a secret, it is possible to
	compute a MAC of the TLS Finished message. An attacker would
	have to negotiate two different TLS connections; one with each
	communicating party. The Finished messages would be different
	in each case, because they depend on the parties' public keys
	(among other things). For this reason, the MACs computed by
	each party would be different.
	It is important to note that authentication techniques which do
	not use the Finished message do not usually provide protection
	from this attack. For example, the client could authenticate
	to the server with a password, but it would still be vulnerable
	to man-in-the-middle attacks.
	Copyright
	ietf-tls-ciphersuite-05 AES Ciphersuites for TLS 14 August 2001
	Copyright (C) The Internet Society 2001. All Rights Reserved.
	This document and translations of it may be copied and furnished to
	others, and derivative works that comment on or otherwise explain
	it or assist in its implementation may be prepared, copied, pub¡
	lished and distributed, in whole or in part, without restriction of
	any kind, provided that the above copyright notice and this para¡
	graph are included on all such copies and derivative works. How¡
	ever, this document itself may not be modified in any way, such as
	by removing the copyright notice or references to the Internet
	Society or other Internet organizations, except as needed for the
	purpose of developing Internet standards in which case the proce¡
	dures for copyrights defined in the Internet Standards process must
	be followed, or as required to translate it into languages other
	than English.
	The limited permissions granted above are perpetual and will not be
	revoked by the Internet Society or its successors or assignees.
	This document and the information contained herein is provided on
	an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGI¡
	NEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
	INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
	INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WAR¡
	RANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
	Intellectual Property
	The IETF takes no position regarding the validity or scope of any
	intellectual property or other rights that might be claimed to per¡
	tain to the implementation or use other technology described in
	this document or the extent to which any license under such rights
	might or might not be available; neither does it represent that it
	has made any effort to identify any such rights. Information on the
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	claims of rights made available for publication and any assurances
	of licenses to be made available, or the result of an attempt made
	to obtain a general license or permission for the use of such pro¡
	prietary rights by implementors or users of this specification can
	be obtained from the IETF Secretariat.
	The IETF invites any interested party to bring to its attention any
	copyrights, patents or patent applications, or other proprietary
	rights which may cover technology that may be required to practice
	this standard. Please address the information to the IETF Executive
	Director.
	ietf-tls-ciphersuite-05 AES Ciphersuites for TLS 14 August 2001
	During the development of the AES, NIST published the following
	statement on intellectual property:
	SPECIAL NOTE - Intellectual Property
	NIST reminds all interested parties that the adoption of
	AES is being conducted as an open standards-setting
	activity. Specifically, NIST has requested that all
	interested parties identify to NIST any patents or inven¡
	tions that may be required for the use of AES. NIST
	hereby gives public notice that it may seek redress under
	the antitrust laws of the United States against any party
	in the future who might seek to exercise patent rights
	against any user of AES that have not been disclosed to
	NIST in response to this request for information.
	One of the authors of Rijndael signed the following disclaimer when
	submitting the algorithm to NIST for consideration in the AES pro¡
	cess:
	I, Joan Daemen, do hereby declare that to the best of my
	knowledge the practice of the algorithm, reference imple¡
	mentation, and mathematically optimized implementations,
	I have submitted, known as Rijndael may be covered by the
	following U.S. and/or foreign patents:
	none
	I do hereby declare that I am aware of no patent applica¡
	tions which may cover the practice of my submitted algo¡
	rithm, reference implementation or mathematically opti¡
	mized implementations.
	I do hereby understand that my submitted algorithm may
	not be selected for inclusion in the Advanced Encryption
	Standard. I also understand and agree that after the
	close of the submission period, my submission may not be
	withdrawn from public consideration for inclusion in the
	Federal Information Processing Standard (FIPS) for
	Advanced Encryption Standard (AES). I further understand
	that I will not receive financial compensation from the
	government for my submission. I certify that, to the
	best of my knowledge, I have fully disclosed all patents
	and patent applications relating to my algorithm. I also
	understand that the U.S. Government may, during the
	course of the lifetime of the AES or during the FIPS pub¡
	lic review process, modify the algorithm's specifications
	(e.g., to protect against a newly discovered
	ietf-tls-ciphersuite-05 AES Ciphersuites for TLS 14 August 2001
	vulnerability). Should my submission be selected for
	inclusion in the AES, I hereby agree not to place any
	restrictions on the use of the algorithm intending it to
	be available on a worldwide, non-exclusive, royalty-free
	basis.
	I do hereby agree to provide the statements for any
	patent or patent application identified to cover practice
	of my algorithm, reference implementation or mathemati¡
	cally optimized implementations and the right to use such
	implementations for the purposes of the AES evaluation
	process.
	I understand that NIST will announce the selected algo¡
	rithm(s) and proceed to publish the draft FIPS for public
	comment. If my algorithm (or the derived algorithm) is
	not selected for inclusion in the FIPS (including those
	not selected for second round of public evaluation), I
	understand that all rights, including use rights of the
	reference and mathematically optimized implementations,
	revert back to the submitter (and other owner[s] as
	appropriate). Additionally, should the U.S. Government
	not select my algorithm for inclusion in the AES after a
	period of four years from the close of the submission
	date for candidate algorithms, all rights revert to the
	submitter (and other owner[s] as appropriate).
	[signed]
	Title: Cryptographer
	Dated: 10-6-98
	Place: Brussels
	The following disclaimer was signed at the start of the second
	"round" of the AES process:
	Dear Mr Foti [of NIST],		Title: Advanced Encryption Standard (AES) Ciphersuites
			for Transport Layer Security (TLS)
			Author(s): P. Chown
			Status: Standards Track
			Date: June 2002
			Mailbox: pc@skygate.co.uk
			Pages: 6
			Characters: 13530
			Updates/Obsoletes/SeeAlso: None
	Hereby we confirm that the original patent and patent		I-D Tag: draft-ietf-tls-ciphersuite-06.txt
	application information, as provided to NIST with our
	original submission in June 1998, has not changed. To
	the best of our knowledge, there are no patents or patent
	applications covering the practice of the algorithm, ref¡
	erence implementation or the mathematically optimized
	implementations.
	ietf-tls-ciphersuite-05 AES Ciphersuites for TLS 14 August 2001		URL: ftp://ftp.rfc-editor.org/in-notes/rfc3268.txt
	[signed]		This document proposes several new ciphersuites. At present, the
	Joan Daemen, Vincent Rijmen		symmetric ciphers supported by Transport Layer Security (TLS) are RC2,
			RC4, International Data Encryption Algorithm (IDEA), Data Encryption
			Standard (DES), and triple DES. The protocol would be enhanced by the
			addition of Advanced Encryption Standard (AES) ciphersuites.
	Acknowledgements		This document is a product of the Transport Layer Security Working
			Group of the IETF.
	I would like to thank the ietf-tls mailing list contributors who		This is now a Proposed Standard Protocol.
	have made helpful suggestions for this document.
	References		This document specifies an Internet standards track protocol for
			the Internet community, and requests discussion and suggestions
			for improvements. Please refer to the current edition of the
			"Internet Official Protocol Standards" (STD 1) for the
			standardization state and status of this protocol. Distribution
			of this memo is unlimited.
	[TLS] T. Dierks, C. Allen, "The TLS Protocol Version 1.0" RFC-2246.		This announcement is sent to the IETF list and the RFC-DIST list.
	January, 1999.		Requests to be added to or deleted from the IETF distribution list
			should be sent to IETF-REQUEST@IETF.ORG. Requests to be
			added to or deleted from the RFC-DIST distribution list should
			be sent to RFC-DIST-REQUEST@RFC-EDITOR.ORG.
	[AES] J. Daemen, V. Rijmen, "The Rijndael Block Cipher"		Details on obtaining RFCs via FTP or EMAIL may be obtained by sending
	http://csrc.nist.gov/encryption/aes/rijndael/Rijndael.pdf 3rd		an EMAIL message to rfc-info@RFC-EDITOR.ORG with the message body
	September 1999.		help: ways_to_get_rfcs. For example:
	[SHA-1] FIPS PUB 180-1, "Secure Hash Standard," National Institute		To: rfc-info@RFC-EDITOR.ORG
	of Standards and Technology, U.S. Department of Commerce, April 17,		Subject: getting rfcs
	1995.
	Author's Address		help: ways_to_get_rfcs
	Pete Chown		Requests for special distribution should be addressed to either the
	Skygate Technology Ltd		author of the RFC in question, or to RFC-Manager@RFC-EDITOR.ORG. Unless
	8 Lombard Road		specifically noted otherwise on the RFC itself, all RFCs are for
	London		unlimited distribution.echo
	SW19 3TZ		Submissions for Requests for Comments should be sent to
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			Authors, for further information.
	Phone: +44 20 8542 7856		Joyce K. Reynolds and Sandy Ginoza
	Email: pc@skygate.co.uk		USC/Information Sciences Institute
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