Near-Collision Attack on the Step-Reduced Compression Function of Skein-256.
Hongbo Yu, Jiazhe Chen, Keting Jia, Xiaoyun Wang · 2011
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.