## Cryptology ePrint Archive: Report 2007/295

Linearization Attacks Against Syndrome Based Hashes

Markku-Juhani O. Saarinen

Abstract: In MyCrypt 2005, Augot, Finiasz, and Sendrier proposed FSB, a family of cryptographic hash functions. The security claim of the FSB hashes is based on a coding theory problem with hard average-case complexity. In the ECRYPT 2007 Hash Function Workshop, new versions with essentially the same compression function but radically different security parameters and an additional final transformation were presented. We show that hardness of average-case complexity of the underlying problem is irrelevant in collision search by presenting a linearization method that can be used to produce collisions in a matter of seconds on a desktop PC for the variant of FSB with claimed $2^128$ security.

Category / Keywords: secret-key cryptography / hash function cryptanalysis, provable security, linearization attack, FSB

Publication Info: INDOCRYPT 2007

Date: received 31 Jul 2007, last revised 25 Sep 2007

Contact author: m saarinen at rhul ac uk

Available format(s): Postscript (PS) | Compressed Postscript (PS.GZ) | PDF | BibTeX Citation

Note: Sample code for matrix arithmetic and pre-image search can be downloaded from: http://www.m-js.com/misc/fsb_test.tar.gz

Short URL: ia.cr/2007/295

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