Paper 2011/323

A New Related-Key Boomerang Distinguishing Attack of Reduced-Round Threefish-256

Shusheng Liu and Libin Wang and Zheng Gong

Abstract

On Nov 2007, NIST announced the SHA-3 competition to select a new hash standard as a replacement of SHA-2. On Dec 2010, five submissions have been selected as the final round candidates, including Skein, which have components based on ARX. In this paper, a new related-key boomerang distinguishing attack is proposed on 31-round Threefish-256 with a time complexity of about $2^{234}$. Our improved attack is based on the efficient algorithms for calculating differentials of modular addition.

Note: Updated version