Improved (related-key) Attacks on Round-Reduced KATAN-32/48/64 Based on the Extended Boomerang Framework

Jiageng Chen, Jesen Teh, Chunhua Su, Azman Samsudin, Junbin Fang

Abstract: The boomerang attack is one of the many extensions of the original differential attack. It has been widely applied to successfully attack many existing ciphers. In this paper, we investigate an extended version of the boomerang attack and show that it is still a very powerful tool especially in the related-key setting. A new branch-and-bound searching strategy which involves the extended boomerang framework is then introduced. We provide an improved cryptanalysis on the KATAN family (a family of hardware-oriented block ciphers proposed in CHES 2009) based on the boomerang attack. In the related-key setting, we were able to greatly improve upon the previous results to achieve the best results, namely 150 and 133 rounds by far for KATAN48/64 respectively. For KATAN32 in the related-key setting and all KATAN variants in the single-key setting, our results are the best ones in the differential setting although inferior to the meet-in-the-middle attack.