Related-Key Boomerang Attacks on KATAN32/48/64

摘要

KATAN/KTANTAN is a family of hardware oriented block ciphers proposed at CHES 2009. Although the KTANTAN family have been broken by a meet-in-the-middle approach, the KATAN family are secure at present. In this paper, we investigate the KATAN family in the related-key boomerang framework with several techniques. By using an efficient differential characteristics search method, long boomerang distinguishers can be built. Furthermore, the key recovery phase is optimized by exploiting several properties of the round function such as the high linearity of the round function and the slow key diffusion. As a result, we can attack 174, 145 and 130 rounds of KATAN32, KATAN48 and KATAN64, which substantially improve the known best results whose attacked rounds are 120, 103, 94 rounds, respectively. Our attacks are confirmed by various experimental verifications, especially, we give concrete right quartets for KATAN32.