< draft-turner-md4-to-historic-10.txt		draft-turner-md4-to-historic-11.txt >
	Network Working Group S. Turner		Network Working Group S. Turner
	Internet-Draft IECA		Internet-Draft IECA
	Obsoletes: 1320 (once approved) L. Chen		Obsoletes: 1320 (once approved) L. Chen
	Intended Status: Informational NIST		Intended Status: Informational NIST
	Expires: June 29, 2011 December 29, 2010		Expires: July 6, 2011 January 6, 2011
	MD4 to Historic Status		MD4 to Historic Status
	draft-turner-md4-to-historic-10.txt		draft-turner-md4-to-historic-11.txt
	Abstract		Abstract
	This document recommends the retirement of MD4 and discusses the		This document retires RFC 1320, which documents the MD4 algorithm,
	reasons for doing so. This document recommends RFC 1320 be moved to		and discusses the reasons for doing so. This document moves RFC 1320
	Historic status.		to Historic status.
	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/.
	skipping to change at page 2, line 5 ¶		skipping to change at page 1, line 50 ¶
	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
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Internet-Draft MD4 to Historic 2010-12-29
	1. Introduction		1. Introduction
			Internet-Draft MD4 to Historic 2011-01-06
	MD4 [MD4] is a message digest algorithm that takes as input a message		MD4 [MD4] is a message digest algorithm that takes as input a message
	of arbitrary length and produces as output a 128-bit "fingerprint" or		of arbitrary length and produces as output a 128-bit "fingerprint" or
	"message digest" of the input. This document recommends that MD4 be		"message digest" of the input. This document retires [MD4].
	retired. Specifically, this document recommends RFC 1320 [MD4] be		Specifically, this document moves RFC 1320 [MD4] to Historic status.
	moved to Historic status. The reasons for taking this action are		The reasons for taking this action are discussed.
	discussed.
	[HASH-Attack] summarizes the use of hashes in many protocols and		[HASH-Attack] summarizes the use of hashes in many protocols and
	discusses how attacks against a message digest algorithm's one-way		discusses how attacks against a message digest algorithm's one-way
	and collision-free properties affect and do not affect Internet		and collision-free properties affect and do not affect Internet
	protocols. Familiarity with [HASH-Attack] is assumed.		protocols. Familiarity with [HASH-Attack] is assumed.
	2. Rationale		2. Rationale
	MD4 was published in 1992 as an Informational RFC. Since its		MD4 was published in 1992 as an Informational RFC. Since its
	publication, MD4 has been under attack [denBORBOS1992] [DOBB1995]		publication, MD4 has been under attack [denBORBOS1992] [DOBB1995]
	skipping to change at page 3, line 5 ¶		skipping to change at page 2, line 52 ¶
	o [RFC1629] Guidelines for OSI NSAP Allocation in the Internet.		o [RFC1629] Guidelines for OSI NSAP Allocation in the Internet.
	Proposed Standard (PS):		Proposed Standard (PS):
	o [RFC3961] Encryption and Checksum Specifications for Kerberos 5.		o [RFC3961] Encryption and Checksum Specifications for Kerberos 5.
	Best Current Practice (BCP):		Best Current Practice (BCP):
	o [RFC4086] Randomness Requirements for Security.		o [RFC4086] Randomness Requirements for Security.
	Internet-Draft MD4 to Historic 2010-12-29
	Informational:		Informational:
			Internet-Draft MD4 to Historic 2011-01-06
	o [RFC1760] The S/KEY One-Time Password System.		o [RFC1760] The S/KEY One-Time Password System.
	o [RFC1983] Internet Users' Glossary.		o [RFC1983] Internet Users' Glossary.
	o [RFC2433] Microsoft PPP CHAP Extensions.		o [RFC2433] Microsoft PPP CHAP Extensions.
	o [RFC2759] Microsoft PPP CHAP Extensions, Version 2.		o [RFC2759] Microsoft PPP CHAP Extensions, Version 2.
	o [RFC3174] US Secure Hash Algorithm 1 (SHA1).		o [RFC3174] US Secure Hash Algorithm 1 (SHA1).
	skipping to change at page 3, line 35 ¶		skipping to change at page 3, line 33 ¶
	Historic or Obsoleted. References and discussions about these RFCs		Historic or Obsoleted. References and discussions about these RFCs
	are omitted. The notable exceptions are:		are omitted. The notable exceptions are:
	o [RFC2313] PKCS #1: RSA Encryption Version 1.5.		o [RFC2313] PKCS #1: RSA Encryption Version 1.5.
	o [RFC2437] PKCS #1: RSA Cryptography Specifications Version 2.0.		o [RFC2437] PKCS #1: RSA Cryptography Specifications Version 2.0.
	o [RFC3447] Public-Key Cryptography Standards (PKCS) #1: RSA		o [RFC3447] Public-Key Cryptography Standards (PKCS) #1: RSA
	Cryptography Specifications Version 2.1.		Cryptography Specifications Version 2.1.
	4. Impact on Moving MD4 to Historic		4. Impact of Moving MD4 to Historic
	The impact of moving MD4 to Historic is minimal with the one		The impact of moving MD4 to Historic is minimal with the one
	exception of Microsoft's use of MD4 as part of RC4-HMAC in Windows,		exception of Microsoft's use of MD4 as part of RC4-HMAC in Windows,
	the as described below.		as described below.
	Regarding DS, PS, and BCP RFCs:		Regarding DS, PS, and BCP RFCs:
	o The initial One-Time Password systems, based on [RFC2289], have		o The initial One-Time Password systems, based on [RFC2289], have
	ostensibly been replaced by HMAC based mechanism, as specified in		ostensibly been replaced by HMAC based mechanism, as specified in
	HOTP: An HMAC-Based One-Time Password Algorithm [RFC4226].		HOTP: An HMAC-Based One-Time Password Algorithm [RFC4226].
	[RFC4226] suggests following recommendations in [RFC4086] for		[RFC4226] suggests following recommendations in [RFC4086] for
	random input, and in [RFC4086] weaknesses of MD4 are discussed.		random input, and in [RFC4086] weaknesses of MD4 are discussed.
	o MD4 was used in the Inter-Domain Routing Protocol (IDRP); each IDRP		o MD4 was used in the Inter-Domain Routing Protocol (IDRP); each IDRP
	message carries a 16-octet hash that is computed by applying the		message carries a 16-octet hash that is computed by applying the
	MD-4 algorithm (RFC 1320) to the context of the message itself.		MD-4 algorithm (RFC 1320) to the context of the message itself.
	Over time IDRP was replaced by BGP-4.		Over time IDRP was replaced by BGP-4 [RFC4271], which required at
			least [MD5].
	o Kerberos Version 5 [RFC3961] specifies the use of MD4 for DES		o Kerberos Version 5 [RFC3961] specifies the use of MD4 for DES
			encryption types and checksum types. They were specified, never
	Internet-Draft MD4 to Historic 2010-12-29		Internet-Draft MD4 to Historic 2011-01-06
	encryption types and checksum types. They were specified, never
	really used, and are in the process of being deprecated by [I-		really used, and are in the process of being deprecated by [I-
	D.des-die-die-die]. Further, the mandatory-to-implement encrypted		D.des-die-die-die]. Further, the mandatory-to-implement encrypted
	types and checksum types specified by Kerberos are based on AES-256		types and checksum types specified by Kerberos are based on AES-256
	and HMAC-SHA1 [RFC3962].		and HMAC-SHA1 [RFC3962].
	Regarding Informational RFCs:		Regarding Informational RFCs:
	o PKCS#1 v1.5 [RFC2313] indicated that there was no reason to not use		o PKCS#1 v1.5 [RFC2313] indicated that there was no reason to not use
	MD4. PKCS#1 v2.0 [RFC2437] and v2.1 [RFC3447] recommend against MD4		MD4. PKCS#1 v2.0 [RFC2437] and v2.1 [RFC3447] recommend against MD4
	due to cryptoanalytic progess having uncovered weaknesses in the		due to cryptoanalytic progess having uncovered weaknesses in the
	skipping to change at page 4, line 38 ¶		skipping to change at page 4, line 37 ¶
	So S/Key was replaced by OTP, at least in theory. Additonally, the		So S/Key was replaced by OTP, at least in theory. Additonally, the
	S/Key implementations in the wild have started to use MD5 in lieu		S/Key implementations in the wild have started to use MD5 in lieu
	of MD4.		of MD4.
	o The CAdES document [RFC5126] lists MD4 as hash algorithm,		o The CAdES document [RFC5126] lists MD4 as hash algorithm,
	disparages it, and then does not mention it again.		disparages it, and then does not mention it again.
	o The SHA-1 document [RFC3174] mentions MD4 in the acknowledgements		o The SHA-1 document [RFC3174] mentions MD4 in the acknowledgements
	section.		section.
	o The three Microsoft RFCs, [RFC2433], [RFC2759], and [RFC4757], are		o The three RFCs describing Microsoft protocols, [RFC2433],
	very widely deployed, MS-CHAP v1, MS-CHAP v2, and RC4-HMAC,		[RFC2759], and [RFC4757], are very widely deployed, MS-CHAP v1, MS-
	respectively.		CHAP v2, and RC4-HMAC, respectively.
	o MS-CHAP Version 1 is supported in Microsoft's Windows XP, 2000,		o MS-CHAP Version 1 is supported in Microsoft's Windows XP, 2000,
	98, 95, NT 4.0, NT 3.51, NT 3.5, but support has been dropped in		98, 95, NT 4.0, NT 3.51, NT 3.5, but support has been dropped in
	Vista. MS-CHAP Version 2 is supported in Microsoft's Windows 7,		Vista. MS-CHAP Version 2 is supported in Microsoft's Windows 7,
	Vista, XP, 2000, 98, 95, and NT 4.0. Both versions of MS-CHAP		Vista, XP, 2000, 98, 95, and NT 4.0. Both versions of MS-CHAP
	are also supported by RADIUS [RFC2548], and EAP [RFC5281]. In		are also supported by RADIUS [RFC2548], and EAP [RFC5281]. In
	2007, [RFC4962] listed MS-CHAP v1 and v2 as flawed and		2007, [RFC4962] listed MS-CHAP v1 and v2 as flawed and
	recommended against their use; these incidents were presented as		recommended against their use; these incidents were presented as
	a strong indication for the necessity of built-in crypto-		a strong indication for the necessity of built-in crypto-
	algorithm agility in AAA protocols.		algorithm agility in AAA protocols.
	o The RC4-HMAC is supported in Microsoft's Windows 2000 and later		o The RC4-HMAC is supported in Microsoft's Windows 2000 and later
	versions of Windows for backwards compatibility with Windows		versions of Windows for backwards compatibility with Windows
	2000. As [RFC4757] stated, RC4-HMAC doesn't rely on the		2000. As [RFC4757] stated, RC4-HMAC doesn't rely on the
			collision resistance property of MD4, but uses it to generate a
	Internet-Draft MD4 to Historic 2010-12-29		Internet-Draft MD4 to Historic 2011-01-06
	collision resistance property of MD4, but uses it to generate a
	key from a password, which is then used as input to HMAC-MD5.		key from a password, which is then used as input to HMAC-MD5.
	For an attacker to recover the password from RC4-HMAC, the		For an attacker to recover the password from RC4-HMAC, the
	attacker first needs to recover the key that is used with HMAC-		attacker first needs to recover the key that is used with HMAC-
	MD5. As noted in [ID.turner-md5-seccon-update], key recovery		MD5. As noted in [ID.turner-md5-seccon-update], key recovery
	attacks on HMAC-MD5 are not yet practical.		attacks on HMAC-MD5 are not yet practical.
	5. Other Considerations		5. Other Considerations
	rsync [RSYNC], a non-IETF protocol, once specified the use of MD4,		rsync [RSYNC], a non-IETF protocol, once specified the use of MD4,
	but as of version 3.0.0 published in 2008 it has adopted MD5 [MD5].		but as of version 3.0.0 published in 2008 it has adopted MD5 [MD5].
	skipping to change at page 6, line 4 ¶		skipping to change at page 5, line 54 ¶
	image attacks on MD4 are practical. It cannot be used as a one-way		image attacks on MD4 are practical. It cannot be used as a one-way
	function. For example, it must not be used to hash a cryptographic		function. For example, it must not be used to hash a cryptographic
	key of 80 bits or longer.		key of 80 bits or longer.
	6.3. HMAC		6.3. HMAC
	The attacks on Hash-based Message Authentication Code (HMAC)		The attacks on Hash-based Message Authentication Code (HMAC)
	algorithms [RFC2104] presented so far can be classified in three		algorithms [RFC2104] presented so far can be classified in three
	types: distinguishing attacks, existential forgery attacks, and key		types: distinguishing attacks, existential forgery attacks, and key
	recovery attacks. Of course, among all these attacks, key recovery		recovery attacks. Of course, among all these attacks, key recovery
	Internet-Draft MD4 to Historic 2010-12-29
	attacks are the most severe attacks.		attacks are the most severe attacks.
			Internet-Draft MD4 to Historic 2011-01-06
	The best results on key recovery attacks on HMAC-MD4 were published		The best results on key recovery attacks on HMAC-MD4 were published
	at EUROCRYPT 2008 with 2^72 queries and 2^77 MD4 computations		at EUROCRYPT 2008 with 2^72 queries and 2^77 MD4 computations
	[WOK2008].		[WOK2008].
	7. Recommendation		7. Recommendation
	Despite MD4 seeing some deployment on the Internet, this		Despite MD4 seeing some deployment on the Internet, this
	specification recommends obsoleting MD4 because MD4 is not a		specification obsoletes [MD4] because MD4 is not a reasonable
	reasonable candidate for further standardization and should be		candidate for further standardization and should be deprecated in
	deprecated in favor of one or more existing hash algorithms (e.g.,		favor of one or more existing hash algorithms (e.g., SHA-256 [SHS]).
	SHA-256 [SHS]).
	RSA Security considers it appropriate to move the MD4 algorithm to		RSA Security considers it appropriate to move the MD4 algorithm to
	Historic status.		Historic status.
	It takes a number of years to deploy crypto and it also takes a		It takes a number of years to deploy crypto and it also takes a
	number of years to withdraw it. Algorithms need to be withdrawn		number of years to withdraw it. Algorithms need to be withdrawn
	before a catastrophic break is discovered. MD4 is clearly showing		before a catastrophic break is discovered. MD4 is clearly showing
	signs of weakness and implementations should strongly consider		signs of weakness and implementations should strongly consider
	removing support and migrating to another hash algorithm.		removing support and migrating to another hash algorithm.
	skipping to change at page 7, line 5 ¶		skipping to change at page 6, line 53 ¶
	pages 194-203, Springer-Verlag, 1992.		pages 194-203, Springer-Verlag, 1992.
	[DOBB1995] H. Dobbertin. Alf swindles Ann. CryptoBytes, 1(3): 5,		[DOBB1995] H. Dobbertin. Alf swindles Ann. CryptoBytes, 1(3): 5,
	1995.		1995.
	[DOBB1996] H. Dobbertin. Cryptanalysis of MD4. In Proceedings of the		[DOBB1996] H. Dobbertin. Cryptanalysis of MD4. In Proceedings of the
	3rd Workshop on Fast Software Encryption, Cambridge, U.K.,		3rd Workshop on Fast Software Encryption, Cambridge, U.K.,
	pages 53-70, Lecture Notes in Computer Science 1039,		pages 53-70, Lecture Notes in Computer Science 1039,
	Springer-Verlag, 1996.		Springer-Verlag, 1996.
	Internet-Draft MD4 to Historic 2010-12-29
	[GLRW2010] Guo, J., Ling, S., Rechberger, C., and H. Wang, "Advanced		[GLRW2010] Guo, J., Ling, S., Rechberger, C., and H. Wang, "Advanced
	Meet-in-the-Middle Preimage Attacks: First Results on Full		Meet-in-the-Middle Preimage Attacks: First Results on Full
			Internet-Draft MD4 to Historic 2011-01-06
	Tiger, and Improved Results on MD4 and SHA-2",		Tiger, and Improved Results on MD4 and SHA-2",
	http://eprint.iacr.org/2010/016.pdf.		http://eprint.iacr.org/2010/016.pdf.
	[HASH-Attack] Hoffman, P., and B. Schneier, "Attacks on Cryptographic		[HASH-Attack] Hoffman, P., and B. Schneier, "Attacks on Cryptographic
	Hashes in Internet Protocols", RFC 4270, November 2005.		Hashes in Internet Protocols", RFC 4270, November 2005.
	[LUER2008] G. Leurent. MD4 is Not One-Way. Fast Software Encryption		[LUER2008] G. Leurent. MD4 is Not One-Way. Fast Software Encryption
	2008, Lausanne, Switzerland, February 10-13, 2008, LNCS		2008, Lausanne, Switzerland, February 10-13, 2008, LNCS
	5086. Springer, 2008.		5086. Springer, 2008.
	skipping to change at page 8, line 5 ¶		skipping to change at page 7, line 53 ¶
	[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-		[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
	Hashing for Message Authentication", RFC 2104, February		Hashing for Message Authentication", RFC 2104, February
	1997.		1997.
	[RFC2433] Zorn, G. and S. Cobb, "Microsoft PPP CHAP Extensions", RFC		[RFC2433] Zorn, G. and S. Cobb, "Microsoft PPP CHAP Extensions", RFC
	2433, October 1998.		2433, October 1998.
	[RFC2437] Kaliski, B., and J. Staddon, "PKCS #1: RSA Cryptography		[RFC2437] Kaliski, B., and J. Staddon, "PKCS #1: RSA Cryptography
	Specifications Version 2.0", RFC 2437, October 1998.		Specifications Version 2.0", RFC 2437, October 1998.
	Internet-Draft MD4 to Historic 2010-12-29
	[RFC2548] Zorn, G., "Microsoft Vendor-specific RADIUS Attributes",		[RFC2548] Zorn, G., "Microsoft Vendor-specific RADIUS Attributes",
	RFC 2548, March 1998.		RFC 2548, March 1998.
			Internet-Draft MD4 to Historic 2011-01-06
	[RFC2759] Zorn, G., "Microsoft PPP CHAP Extensions, Version 2", RFC		[RFC2759] Zorn, G., "Microsoft PPP CHAP Extensions, Version 2", RFC
	2759, January 2000.		2759, January 2000.
	[RFC3174] Eastlake, D. and P. Jones, "US Secure Hash Algorithm 1		[RFC3174] Eastlake, D. and P. Jones, "US Secure Hash Algorithm 1
	(SHA1)", RFC 3174, September 2001.		(SHA1)", RFC 3174, September 2001.
	[RFC3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography		[RFC3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography
	Standards (PKCS) #1: RSA Cryptography Specifications		Standards (PKCS) #1: RSA Cryptography Specifications
	Version 2.1" RFC 3447, February 2003.		Version 2.1" RFC 3447, February 2003.
	skipping to change at page 8, line 34 ¶		skipping to change at page 8, line 31 ¶
	for Kerberos 5", RFC 3962, February 2005.		for Kerberos 5", RFC 3962, February 2005.
	[RFC4086] R Eastlake, D., 3rd, Schiller, J., and S. Crocker,		[RFC4086] R Eastlake, D., 3rd, Schiller, J., and S. Crocker,
	"Randomness Requirements for Security", BCP 106, RFC 4086,		"Randomness Requirements for Security", BCP 106, RFC 4086,
	June 2005.		June 2005.
	[RFC4226] Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E.		[RFC4226] Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E.
	Nordmark, "Mobile IP Version 6 Route Optimization Security		Nordmark, "Mobile IP Version 6 Route Optimization Security
	Design Background", RFC 4226, December 2005.		Design Background", RFC 4226, December 2005.
			[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
			Protocol 4 (BGP-4)", RFC 4271, January 2006.
	[RFC4757] Jaganathan, K., Zhu, L., and J. Brezak, "The RC4-HMAC		[RFC4757] Jaganathan, K., Zhu, L., and J. Brezak, "The RC4-HMAC
	Kerberos Encryption Types Used by Microsoft Windows," RFC		Kerberos Encryption Types Used by Microsoft Windows," RFC
	4757, December 2006.		4757, December 2006.
	[RFC4962] Housley, R., and Aboba, B., "Guidance for Authentication,		[RFC4962] Housley, R., and Aboba, B., "Guidance for Authentication,
	Authorization, and Accounting (AAA) Key Management", RFC		Authorization, and Accounting (AAA) Key Management", RFC
	4962, July 2007.		4962, July 2007.
	[RFC5126] Pinkas, D., Pope, N., and J. Ross, "CMS Advanced Electronic		[RFC5126] Pinkas, D., Pope, N., and J. Ross, "CMS Advanced Electronic
	Signatures (CAdES)", RFC 5126, February 2008.		Signatures (CAdES)", RFC 5126, February 2008.
	skipping to change at page 9, line 5 ¶		skipping to change at page 9, line 5 ¶
	Protocol Tunneled Transport Layer Security Authenticated		Protocol Tunneled Transport Layer Security Authenticated
	Protocol Version 0 (EAP-TTLSv0)", RFC 5281, August 2008.		Protocol Version 0 (EAP-TTLSv0)", RFC 5281, August 2008.
	[ID.turner-md5-seccon-update] Turner, S., and L. Chen, "Updated		[ID.turner-md5-seccon-update] Turner, S., and L. Chen, "Updated
	Security Considerations for the MD5 Message-Digest and the		Security Considerations for the MD5 Message-Digest and the
	HMAC-MD5 Algorithms," draft-turner-md5-seccon-update, work-		HMAC-MD5 Algorithms," draft-turner-md5-seccon-update, work-
	in-progress.		in-progress.
	[RSA-AdviceOnMD4] Robshaw, M.J.B., "On Recent Results for MD2, MD4		[RSA-AdviceOnMD4] Robshaw, M.J.B., "On Recent Results for MD2, MD4
	Internet-Draft MD4 to Historic 2010-12-29		Internet-Draft MD4 to Historic 2011-01-06
	and MD5", November 1996,		and MD5", November 1996,
	ftp://ftp.rsasecurity.com/pub/pdfs/bulletn4.pdf		ftp://ftp.rsasecurity.com/pub/pdfs/bulletn4.pdf
	[RSYNC] http://www.samba.org/rsync/		[RSYNC] http://www.samba.org/rsync/
	[SHS] National Institute of Standards and Technology (NIST), FIPS		[SHS] National Institute of Standards and Technology (NIST), FIPS
	Publication 180-3: Secure Hash Standard, October 2008.		Publication 180-3: Secure Hash Standard, October 2008.
	[SP800-57] National Institute of Standards and Technology (NIST),		[SP800-57] National Institute of Standards and Technology (NIST),
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