Cryptology ePrint Archive: Report 2008/272

A New Hash Family Obtained by Modifying the SHA-2 Family

Somitra Kumar Sanadhya and Palash Sarkar

Abstract: In this work, we study several properties of the SHA-2 design which have been utilized in recent collision attacks against reduced round SHA-2. Small modifications to the SHA-2 design are suggested to thwart these attacks. The modified round function provides the same resistance to linearization attacks as the original SHA-2 round function, but, provides better resistance to non-linear attacks. Our next contribution is to introduce the general idea of ``multiple feed-forward" for the construction of cryptographic hash functions. This can provide increased resistance to the Chabaud-Joux type ``perturbation-correction'' collision attacks. The idea of feed-forward is taken further by introducing the idea of feed-forward across message blocks leading to resistance against generic multi-collision attacks. The net effect of the suggested changes to the SHA-2 design has insignificant impact on the efficiency of computing the digest.

Category / Keywords: SHA-2 hash family, non-randomness, hash function design.

Publication Info: Accepted at ASIACCS 2009.

Date: received 12 Jun 2008, last revised 11 Feb 2010

Contact author: somitra_r at isical ac in

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

Note: Rectified an error in the pseudo-code in Fig 1. We thank Jinmin Zhong for bringing this to our attention.

Version: 20100211:101345 (All versions of this report)

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