One document matched: draft-turner-md5-seccon-update-06.txt
Differences from draft-turner-md5-seccon-update-05.txt
Network Working Group S. Turner
Internet Draft IECA
Updates: 1321, 2104 (once approved) L. Chen
Intended Status: Informational NIST
Expires: April 25, 2011 October 25, 2010
Updated Security Considerations for the
MD5 Message-Digest and the HMAC-MD5 Algorithms
draft-turner-md5-seccon-update-06.txt
Abstract
This document updates the security considerations for the MD5 message
digest algorithm. It also updates the security considerations for
HMAC-MD5.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. This document may contain material
from IETF Documents or IETF Contributions published or made publicly
available before November 10, 2008.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on April 25, 2011.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
Turner & Chen Expires April 25, 2011 [Page 1]
Internet-Draft MD5 and HMAC-MD5 Security Considerations Oct 2010
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
1. Introduction
MD5 [MD5] is a message digest algorithm that takes as input a message
of arbitrary length and produces as output a 128-bit "fingerprint" or
"message digest" of the input. The published attacks against MD5
show that it is not prudent to use MD5 when collision resistance is
required. This document replaces the security considerations in RFC
1321 [MD5].
[HMAC] defined a mechanism for message authentication using
cryptographic hash functions. Any message digest algorithm can be
used, but the cryptographic strength of HMAC depends on the
properties of the underlying hash function. [HMAC-MD5] defined test
cases for HMAC-MD5. This document updates the security
considerations in [HMAC-MD5].
[HASH-Attack] summarizes the use of hashes in many protocols and
discusses how attacks against a message digest algorithm's one-way
and collision-free properties affect and do not affect Internet
protocols. Familiarity with [HASH-Attack] is assumed.
2. Security Considerations
MD5 was published in 1992 as an Informational RFC. Since that time,
MD5 has been studied extensively. What follows are recent attacks
against MD5's collisions, pre-image, and second pre-image resistance.
Additionally, attacks against MD5 used in message authentication with
a shared secret (i.e., HMAC-MD5) are discussed.
Some may find the guidance for key lengths and algorithm strengths in
[SP800-57] and [SP800-131] useful.
2.1. Collision Resistance
Psuedo-collisions for the compress function of MD5 were first
described in 1993 [denBBO1993]. In 1996, [DOB1995] demonstrated a
collision pair for the MD5 compression function with a chosen initial
value. The first paper that demonstrated two collision pairs for
Turner & Chen Expires April 25, 2011 [Page 2]
Internet-Draft MD5 and HMAC-MD5 Security Considerations Oct 2010
regular MD5 was published in 2004 [WFLY2004]. The detailed attack
techniques for MD5 were published at EUROCRYPT 2005 [WAYU2005]. Since
then, a lot of research results have been published to improve
collision attacks on MD5. The attacks presented in [KLIM2006] can
find MD5 collision in about one minute on a standard notebook PC
(Intel Pentium, 1.6 GHz.). [STEV2007] claims that it takes 10
seconds or less on a 2.6Ghz Pentium4 to find collisions. In
[STEV2007][SLdeW2007][SSALMOdeW2009][SLdeW2009], the collision
attacks on MD5 were successfully applied to X.509 certificates.
Notice that the collision attack on MD5 can also be applied to
password based challenge-and-response authentication protocols such
as the APOP option in the Post Office Protocol (POP) used in post
office authentication as presented in [LEUR2007].
In fact, more delicate attacks on MD5 to improve the speed of finding
collisions have been published recently. However, the aforementioned
results have provided sufficient reason to eliminate MD5 usage in
applications where collision resistance is required such as digital
signatures.
2.2. Pre-image and Second Pre-image Resistance
Even though the best result can find a pre-image attack of MD5 faster
than exhaustive search as presented in [SAAO2009], the complexity
2^123.4 is still pretty high.
2.3. HMAC
The cryptanalysis of HMAC-MD5 is usually conducted together with NMAC
(Nested MAC) since they are closely related. NMAC uses two
independent keys K1 and K2 such that NMAC(K1, K2, M) = H(K1, H(K2,
M), where K1 and K2 are used as secret IVs for hash functions
H(IV,M). If we re-write the HMAC equation using two secret IVs such
that IV2 = H(K Xor ipad) and IV1 = H(K Xor opad), then HMAC(K, M) =
NMAC(IV1, IV2, M). Here it is very important to notice that IV1 and
IV2 are not independently selected.
The first analysis was explored on NMAC-MD5 using related keys in
[COYI2006]. The partial key recovery attack cannot be extended to
HMAC-MD5, since for HMAC, recovering partial secret IVs can hardly
lead to recovering (partial) key K. Another paper presented at Crypto
2007 [FLN2007] extended results of [COYI2006] to a full key recovery
attack on NMAC-MD5. Since it also uses related key attack, it does
not seem applicable to HMAC-MD5.
A EUROCRYPT 2009 paper presented a distinguishing attack on HMAC-MD5
[WYWZZ2009] without using related keys. It can distinguish an
Turner & Chen Expires April 25, 2011 [Page 3]
Internet-Draft MD5 and HMAC-MD5 Security Considerations Oct 2010
instantiation of HMAC with MD5 from an instantiation with a random
function with 2^97 queries with probability 0.87. This is called
distinguishing-H. Using the distinguishing attack, it can recover
some bits of the intermediate status of the second block. However, as
it is pointed out in [WYWZZ2009], it cannot be used to recover the
(partial) inner key H(K Xor ipad). It is not obvious how the attack
can be used to form a forgery attack either.
The attacks on HMAC-MD5 do not seem to indicate a practical
vulnerability when used as a message authentication code. Considering
that the distinguishing-H attack is different from a distinguishing-R
attack, which distinguishes an HMAC from a random function, the
practical impact on HMAC usage as a PRF such as in a key derivation
function is not well understood.
Therefore, it may not be urgent to remove HMAC-MD5 from the existing
protocols. However, since MD5 must not be used for digital
signatures, for a new protocol design, a ciphersuite with HMAC-MD5
should not be included. Options include HMAC-SHA256 [HMAC][HMAC-
SHA256] and [AES-CMAC] when AES is more readily available than a hash
function.
3. IANA Considerations
IANA is requested to update the md5 usage entry in the Hash Function
Textual Names registry by replacing "COMMON" with "DEPRECATED".
4. Acknowledgements
Obviously, we have to thank all the cryptographers who produced the
results we refer to in this document. We'd also like to thank Alfred
Hoenes, Martin Rex, and Benne de Weger for their comments.
5. Normative References
[AES-CMAC] Song, J., Poovendran, R., Lee., J., and T. Iwata,
"The AES-CMAC Algorithm", RFC 4493, June 2006.
[COYI2006] S. Contini, Y.L. Yin. Forgery and partial key-
recovery attacks on HMAC and NMAC using hash
collisions. ASIACRYPT 2006. LNCS 4284, Springer,
2006.
[denBBO1993] den Boer, B. and A. Bosselaers, "Collisions for the
compression function of MD5", Eurocrypt 1993.
[DOB1995] Dobbertin, H., "Cryptanalysis of MD5 Compress",
Eurocrypt 1996.
Turner & Chen Expires April 25, 2011 [Page 4]
Internet-Draft MD5 and HMAC-MD5 Security Considerations Oct 2010
[FLN2007] Fouque, P.-A., Leurent, G., Nguyen, P.Q.: Full key-
recovery attacks on HMAC/NMAC-MD4 and NMAC-MD5.
CRYPTO 2007. LNCS, 4622, Springer, 2007.
[HASH-Attack] Hoffman, P., and B. Schneier, "Attacks on
Cryptographic Hashes in Internet Protocols", RFC
4270, November 2005.
[HMAC] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC:
Keyed-Hashing for Message Authentication", RFC
2104, February 1997.
[HMAC-MD5] Cheng, P., and R. Glenn, "Test Cases for HMAC-MD5
and HMAC-SHA-1", RC 2201, September 1997.
[HMAC-SHA256] Nystrom, M., "Identifiers and Test Vectors for
HMAC-SHA-224, HMAC-SHA-256, HMAC-SHA-384, and
HMAC-SHA-512", RFC 4231, December 2005.
[KLIM2006] V. Klima. Tunnels in Hash Functions: MD5 Collisions
within a Minute. Cryptology ePrint Archive, Report
2006/105 (2006), http://eprint.iacr.org/2006/105.
[LEUR2007] G. Leurent, Message freedom in MD4 and MD5
collisions: Application to APOP. Proceedings of
FSE 2007. Lecture Notes in Computer Science 4715.
Springer 2007.
[MD5] Rivest, R., "The MD5 Message-Digest Algorithm", RFC
1321, April 1992.
[SAAO2009] Y. Sasaki and K. Aoki. Finding preimages in full
MD5 faster than exhaustive search. Advances in
Cryptology - EUROCRYPT 2009, LNCS 5479 of Lecture
Notes in Computer Science, Springer, 2009.
[SLdeW2007] Stevens, M., Lenstra, A., de Weger, B., Chosen-
prefix Collisions for MD5 and Colliding X.509
Certificates for Different Identities. EuroCrypt
2007.
[SLdeW2009] Stevens, M., Lenstra, A., de Weger, B., "Chosen-
prefix Collisions for MD5 and Applications",
Journal of Cryptology, 2009.
http://deweger.xs4all.nl/papers/%5B42%5DStLedW-
MD5-JCryp%5B2009%5D.pdf.
Turner & Chen Expires April 25, 2011 [Page 5]
Internet-Draft MD5 and HMAC-MD5 Security Considerations Oct 2010
[SSALMOdeW2009] Stevens, M., Sotirov, A., Appelbaum, J., Lenstra,
A., Molnar, D., Osvik, D., and B. de Weger. Short
chosen-prefix collisions for MD5 and the creation
of a rogue CA certificate, Crypto 2009.
[SP800-57] National Institute of Standards and Technology
(NIST), Special Publication 800-57: Recommendation
for Key Management - Part 1 (Revised), March 2007.
[SP800-131] National Institute of Standards and Technology
(NIST), Special Publication 800-131: DRAFT
Recommendation for the Transitioning of
Cryptographic Algorithms and Key Sizes, June 2010.
[STEV2007] Stevens, M., On Collisions for MD5.
http://www.win.tue.nl/hashclash/On%20Collisions%20
for%20MD5%20-%20M.M.J.%20Stevens.pdf.
[WAYU2005] X. Wang and H. Yu. How to Break MD5 and other Hash
Functions. LNCS 3494. Advances in Cryptology -
EUROCRYPT2005, Springer 2005.
[WFLY2004] X. Wang, D. Feng, X. Lai, H. Yu, Collisions for
Hash Functions MD4, MD5, HAVAL-128 and RIPEMD,
2004, http://eprint.iacr.org/2004/199.pdf
[WYWZZ2009] X. Wang, H. Yu, W. Wang, H. Zhang, and T. Zhan.
Cryptanalysis of HMAC/NMAC-MD5 and MD5-MAC. LNCS
5479. Advances in Cryptology - EUROCRYPT2009,
Springer 2009.
Turner & Chen Expires April 25, 2011 [Page 6]
Internet-Draft MD5 and HMAC-MD5 Security Considerations Oct 2010
Authors' Addresses
Sean Turner
IECA, Inc.
3057 Nutley Street, Suite 106
Fairfax, VA 22031
USA
EMail: turners@ieca.com
Lily Chen
National Institute of Standards and Technology
100 Bureau Drive, Mail Stop 8930
Gaithersburg, MD 20899-8930
USA
EMail: lily.chen@nist.gov
Turner & Chen Expires April 25, 2011 [Page 7]| PAFTECH AB 2003-2026 | 2026-04-23 04:01:31 |