Cryptology ePrint Archive: Report 2011/148

Near-Collision Attack on the Step-Reduced Compression Function of Skein-256

Hongbo Yu and Jiazhe Chen and Ketingjia and Xiaoyun Wang

Abstract: The Hash function Skein is one of the 5 finalists of NIST SHA-3 competition. It is designed based on the threefish block cipher and it only uses three primitive operations: modular addition, rotation and bitwise XOR (ARX). In this paper, we combine two short differential paths to a long differential path using the modular differential technique. And we present the semi-free start near-collision attack up to the 32-step Skein-256 with the Hamming difference 51. The complexity of our attack is about $2^{105}$.

Category / Keywords: Hash function, Skein, SHA-3

Date: received 23 Mar 2011, last revised 31 Mar 2011

Contact author: yuhongbo at mail tsinghua edu cn

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Version: 20110401:014408 (All versions of this report)

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