Cryptology ePrint Archive: Report 2007/395

Second Preimage Attacks on Dithered Hash Functions

Charles Bouillaguet and Pierre-Alain Fouque and Adi Shamir and Sebastien Zimmer

Abstract: The goal of this paper is to analyze the security of dithered variants of the Merkle-Damgard mode of operation that use a third input to indicate the position of a block in the message to be hashed. These modes of operation for hash functions have been proposed to avoid some structural weaknesses of the Merkle-Damgard paradigm, e.g. that second preimages can be constructed in much less than $2^n$ work, as pointed out by Kelsey and Schneier. Among the modes of operation that use such a third input are Rivest's dithered hashing and Biham and Dunkelman's HAIFA proposal. We propose several new second preimage attacks on the Merkle-Damgard mode of operation, which can also attack Rivest's dithered hash with almost the same complexity. When applied to Shoup's UOWHF, these attacks can be shown to be optimal since their complexity matches Shoup's security bound.

Category / Keywords: secret-key cryptography / Cryptanalysis, Hash Function, Dithering

Publication Info: Submitted to EUROCRYPT'08

Date: received 12 Oct 2007

Contact author: charles bouillaguet at ens fr

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Version: 20071014:182654 (All versions of this report)

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