The Boomerang Attacks on the Round-Reduced Skein-512
نویسندگان
چکیده
The hash function Skein is one of the five finalists of the NIST SHA-3 competition; it is based on the block cipher Threefish which only uses three primitive operations: modular addition, rotation and bitwise XOR (ARX). This paper studies the boomerang attacks on Skein-512. Boomerang distinguishers on the compression function reduced to 32 and 36 rounds are proposed, with complexities 2 and 2 respectively. Examples of the distinguishers on 28-round and 31round are also given. In addition, the boomerang distinguishers are applicable to the key-recovery attacks on reduced Threefish-512. The complexities for key-recovery attacks reduced to 32-/33/34-round are about 2, 2 and 2. Because Laurent et al. [14] pointed out that the previous boomerang distinguishers for Threefish-512 are in fact not compatible, our attacks are the first valid boomerang attacks for the final round Skein-512.
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