## Cryptology ePrint Archive: Report 2010/057

Message Recovery and Pseudo-Preimage Attacks on the Compression Function of Hamsi-256

Cagdas Calik and Meltem Sonmez Turan

Abstract: Hamsi is one of the second round candidates of the SHA-3 competition. In this study, we present non-random differential properties for the compression function of the hash function Hamsi-256. Based on these properties, we first demonstrate a distinguishing attack that requires a few evaluations of the compression function and extend the distinguisher to 5 rounds with complexity $2^{83}$. Then, we present a message recovery attack with complexity of $2^{10.48}$ compression function evaluations. Also, we present a pseudo-preimage attack for the compression function with complexity $2^{254.25}$. The pseudo-preimage attack on the compression function is easily converted to a pseudo second preimage attack on Hamsi-256 hash function with the same complexity.

Category / Keywords: secret-key cryptography / Hash functions, SHA-3 competition, cryptanalysis, preimage attacks

Date: received 2 Feb 2010, last revised 15 Feb 2010

Contact author: meltemsturan at gmail com

Available format(s): PDF | BibTeX Citation

Short URL: ia.cr/2010/057

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