Improved differential meet-in-the-middle attack using S-box linearization

The S-box linearization technology is proposed in 2020 by Jian Guo et al. They transform the S-box into linear component by adding restrictions to the plaintext space. Boura et al propose differential meet-in-the-middle cryptanalysis in 2023. Ahmadian et al improve the attack by introducing probabilistic key recovery and state-test technique at Eurocrypt 2024. This paper combines these techniques and proposes an improved differential MITM attack against SPN structure ciphers using S-box linearization technique, called S-box linearized differential MITM attack. It can extend the maximum rounds of differential MITM attacks without significantly increasing time complexity. A general framework of the attack is given and we successfully apply it to 24-round CRAFT with time complexity 2124.51 2 124.51 , data complexity 2⁶⁰ 2 60 and memory complexity 257.58 2 57.58 , improving the previous best known attack by one round in single key setting.