关键词: 线性密码分析, 线性偏差表达式, 密码, S盒

Abstract:

Proposes a method for seeking the upper bounds of maximum linear bias for these ciphers. This technique consists of two steps. Firstly, we give the mathematical relationship between linear bias of ciphers and linear bias of round function F and S box respectively by carrying out strictly mathematical expression of linear bias for ciphers. Next we determine the upper bounds of linear bias for ciphers. Using this method we give the upper bounds of linear bias within 32 rounds.

Key words: linear cryptanalysis, linear bias expression, ciphers, S-box