IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences
Online ISSN : 1745-1337
Print ISSN : 0916-8508
Special Section on Cryptography and Information Security
Near-Collision Attacks on MD4: Applied to MD4-Based Protocols
Lei WANGKazuo OHTANoboru KUNIHIRO
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2009 Volume E92.A Issue 1 Pages 76-86

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Abstract

The most widely used hash functions from MD4 family have been broken, which lead to a public competition on designing new hash functions held by NIST. This paper focuses on one concept called near-collision resistance: computationally difficult to find a pair of messages with hash values differing in only few bits, which new hash functions should satisfy. In this paper, we will give a model of near-collisions on MD4, and apply it to attack protocols including HMAC/NMAC-MD4 and MD4(Password||Challenge). Our new outer-key recovery attacks on HMAC/NMAC-MD4 has a complexity of 272 online queries and 277 MD4 computations, while previous result was 288 online queries and 295 MD4 computations. Our attack on MD4(Password||Challenge) can recover 16 password characters with a complexity of 237 online queries and 221 MD4 computations, which is the first approach to attack such protocols.

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© 2009 The Institute of Electronics, Information and Communication Engineers
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