Improved Related-Key Boomerang Cryptanalysis of AES-256

A specific class of differential cryptanalytic approach, known as Related Key Boomerang Attack, has been successfully applied to several symmetric cryptographic primitives in particular encryption schemes such as Advanced Encryption Standard (AES). In this paper, we propose a new related-key boomerang attack on 8-round AES-256, a couple of ones on 9round following the work of Gorski et al. In the first one, we attacked 8-round AES-256 with the time complexity of 2⁷⁹ and the data complexity of 2⁵⁹. The extended 8-round attack on 9round AES-256 is more efficient than previous attacks from both time and data complexity perspectives.