## Cryptology ePrint Archive: Report 2008/183

Preimage Attacks on 3-Pass HAVAL and Step-Reduced MD5

Jean-Philippe Aumasson and Willi Meier and Florian Mendel

Abstract: This paper presents preimage attacks for the hash functions 3-pass HAVAL and step-reduced MD5. Introduced in 1992 and 1991 respectively, these functions underwent severe collision attacks, but no preimage attack. We describe two preimage attacks on the compression function of 3-pass HAVAL. The attacks have a complexity of about $2^{224}$ compression function evaluations instead of $2^{256}$. Furthermore, we present several preimage attacks on the MD5 compression function that invert up to 47 (out of 64) steps within $2^{96}$ trials instead of $2^{128}$. Though our attacks are not practical, they show that the security margin of 3-pass HAVAL and step-reduced MD5 with respect to preimage attacks is not as high as expected.

Category / Keywords: cryptanalysis, hash function, preimage attack

Publication Info: Accepted to SAC 2008

Date: received 23 Apr 2008, last revised 1 Jul 2008

Contact author: jeanphilippe aumasson at gmail com

Available format(s): PDF | BibTeX Citation

Note: Revised version

Short URL: ia.cr/2008/183

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