< draft-ietf-ipsec-ah-md5-02.txt		draft-ietf-ipsec-ah-md5-03.txt >
	Network Working Group P Metzger		Network Working Group P Metzger
	Internet Draft W A Simpson		Internet Draft W A Simpson
	expires in six months March 1995		expires in six months April 1995
	IP Authentication using Keyed MD5		IP Authentication using Keyed MD5
	draft-ietf-ipsec-ah-md5-02.txt |		draft-ietf-ipsec-ah-md5-03.txt |
	Status of this Memo		Status of this Memo
	This document is a submission to the IP Security Working Group of the		This document is a submission to the IP Security Working Group of the
	Internet Engineering Task Force (IETF). Comments should be submitted		Internet Engineering Task Force (IETF). Comments should be submitted
	to the ipsec@ans.net mailing list.		to the ipsec@ans.net mailing list.
	Distribution of this memo is unlimited.		Distribution of this memo is unlimited.
	This document is an Internet-Draft. Internet Drafts are working		This document is an Internet-Draft. Internet Drafts are working
	skipping to change at page 1, line 56 ¶		skipping to change at page 1, line 56 ¶
	The Authentication Header (AH) [A-AH] provides integrity and		The Authentication Header (AH) [A-AH] provides integrity and
	authentication for IP datagrams.		authentication for IP datagrams.
	This specification describes the AH use of Message Digest 5 (MD5)		This specification describes the AH use of Message Digest 5 (MD5)
	[RFC-1321].		[RFC-1321].
	All implementations that claim conformance or compliance with the		All implementations that claim conformance or compliance with the
	Authentication Header specification MUST implement this MD5		Authentication Header specification MUST implement this MD5
	mechanism.		mechanism.
	Implementors should consult the most recent version of the IAB		Implementors should consult the most recent version of the IAB |
	Standards [RFC-1610] for further guidance on the status of this		Standards [RFC-1720] for further guidance on the status of this
	document.		document.
	This document assumes that the reader is familiar with the related		This document assumes that the reader is familiar with the related
	document "Security Architecture for the Internet Protocol" [A-SA],		document "Security Architecture for the Internet Protocol" [A-SA],
	which defines the overall security plan for IP, and provides		which defines the overall security plan for IP, and provides
	important background for this specification.		important background for this specification.
	1.1. Keys		1.1. Keys
	The secret authentication key shared between the communicating		The secret authentication key shared between the communicating
	skipping to change at page 2, line 11 ¶		skipping to change at page 2, line 11 ¶
	alternative authentication algorithms that have significantly		alternative authentication algorithms that have significantly
	faster throughput, are not patent-encumbered, and still retain		faster throughput, are not patent-encumbered, and still retain
	adequate cryptographic strength.		adequate cryptographic strength.
	2. Calculation		2. Calculation
	The 128-bit digest is calculated as described in [RFC-1321]. The		The 128-bit digest is calculated as described in [RFC-1321]. The
	specification of MD5 includes a portable 'C' programming language		specification of MD5 includes a portable 'C' programming language
	description of the MD5 algorithm.		description of the MD5 algorithm.
	The invariant fields of the entire IP datagram are hashed first. The		The variable length secret authentication key is zero-filled to the |
	variable length secret authentication key is concatenated with		next 128-bit boundary, concatenated with (immediately followed by) |
	(immediately followed by) this initial 128-bit digest, and the		the invariant fields of the entire IP datagram, concatenated with |
	combination is hashed again. This final 128-bit digest is inserted		(immediately followed by) the variable length secret authentication |
	into the Authentication Data field.		key again (trailing padding is added by the MD5 algorithm). The |
			resulting 128-bit digest is inserted into the Authentication Data |
			field.
	The MD5 algorithm requires a particular format of padding after the *		Care must be taken that the keys and padding are not sent over the |
	end of the authenticated data. This padding is not sent over the		link.
	link. *
	Security Considerations		Security Considerations
	Users need to understand that the quality of the security provided by		Users need to understand that the quality of the security provided by
	this specification depends completely on the strength of the MD5 hash		this specification depends completely on the strength of the MD5 hash
	function, the correctness of that algorithm's implementation, the		function, the correctness of that algorithm's implementation, the
	security of the key management mechanism and its implementation, the		security of the key management mechanism and its implementation, the
	strength of the key [CN94], and upon the correctness of the		strength of the key [CN94], and upon the correctness of the
	implementations in all of the participating nodes.		implementations in all of the participating nodes.
	skipping to change at page 3, line 13 ¶		skipping to change at page 3, line 13 ¶
	move in the near future to algorithms with longer hash lengths.		move in the near future to algorithms with longer hash lengths.
	Acknowledgements		Acknowledgements
	Some of the text of this specification was derived from work by		Some of the text of this specification was derived from work by
	Randall Atkinson for the SIP, SIPP, and IPv6 Working Groups.		Randall Atkinson for the SIP, SIPP, and IPv6 Working Groups.
	The basic concept and use of MD5 is derived in large part from the		The basic concept and use of MD5 is derived in large part from the
	work done for SNMPv2 [RFC-1446].		work done for SNMPv2 [RFC-1446].
	Burt Kaliski suggested the two step keyed-MD5 technique.		Steve Bellovin, Steve Deering, Frank Kastenholz, Charles Lynn, and *
	Steve Bellovin, Steve Deering, Frank Kastenholz, Charles Lynn, and
	Dave Mihelcic provided useful critiques of earlier versions of this		Dave Mihelcic provided useful critiques of earlier versions of this
	draft.		draft.
	References		References
	[A-SA] Randall Atkinson, "Security Architecture for the Internet		[A-SA] Randall Atkinson, "Security Architecture for the Internet
	Protocol", work in progress.		Protocol", work in progress.
	[A-AH] Randall Atkinson, "IP Authentication Header", work in		[A-AH] Randall Atkinson, "IP Authentication Header", work in
	progress.		progress.
	skipping to change at page 3, line 43 ¶		skipping to change at page 3, line 41 ¶
	253-280, July 1994.		253-280, July 1994.
	[RFC-1321]		[RFC-1321]
	Ronald Rivest, "The MD5 Message-Digest Algorithm", RFC-1321,		Ronald Rivest, "The MD5 Message-Digest Algorithm", RFC-1321,
	DDN Network Information Center, April 1992.		DDN Network Information Center, April 1992.
	[RFC-1446]		[RFC-1446]
	Galvin, J., and McCloghrie, K., "Security Protocols for		Galvin, J., and McCloghrie, K., "Security Protocols for
	Version 2 of the Simple Network Management Protocol		Version 2 of the Simple Network Management Protocol
	(SNMPv2)", RFC-1446, DDN Network Information Center, April		(SNMPv2)", RFC-1446, DDN Network Information Center, April
	1993.		1993. *
	[RFC-1610]
	Postel, J., "Internet Official Protocol Standards", STD 1,
	RFC 1610, USC/Information Sciences Institute, July 1994.
	[RFC-1700]		[RFC-1700]
	Reynolds, J., and Postel, J., "Assigned Numbers", STD 2, RFC		Reynolds, J., and Postel, J., "Assigned Numbers", STD 2, RFC
	1700, USC/Information Sciences Institute, October 1994.		1700, USC/Information Sciences Institute, October 1994. |
			[RFC-1720] |
			Postel, J., "Internet Official Protocol Standards", STD 1, |
			RFC 1720, USC/Information Sciences Institute, November 1994.
	[OW94] Paul C. van Oorschot & Michael J. Wiener, "Parallel		[OW94] Paul C. van Oorschot & Michael J. Wiener, "Parallel
	Collision Search with Application to Hash Functions and		Collision Search with Application to Hash Functions and
	Discrete Logarithms", Proceedings of the 2nd ACM Conf.		Discrete Logarithms", Proceedings of the 2nd ACM Conf.
	Computer and Communications Security, Fairfax, VA, Nov 3-5		Computer and Communications Security, Fairfax, VA, Nov 3-5
	1994.		1994.
	[Schneier94]		[Schneier94]
	Schneier, B., "Applied Cryptography", John Wiley & Sons, New		Schneier, B., "Applied Cryptography", John Wiley & Sons, New
	York, NY, 1994. ISBN 0-471-59756-2		York, NY, 1994. ISBN 0-471-59756-2
	skipping to change at line 221 ¶		skipping to change at line 220 ¶
	1. Introduction .......................................... 1		1. Introduction .......................................... 1
	1.1 Keys ............................................ 1		1.1 Keys ............................................ 1
	1.2 Data Size ....................................... 1		1.2 Data Size ....................................... 1
	1.3 Performance ..................................... 1		1.3 Performance ..................................... 1
	2. Calculation ........................................... 2		2. Calculation ........................................... 2
	SECURITY CONSIDERATIONS ...................................... 2		SECURITY CONSIDERATIONS ...................................... 2
	ACKNOWLEDGEMENTS ............................................. 2		ACKNOWLEDGEMENTS ............................................. 3
	REFERENCES ................................................... 3		REFERENCES ................................................... 3
	AUTHOR'S ADDRESS ............................................. 4		AUTHOR'S ADDRESS ............................................. 4
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