针对一类广义Feistel密码提出一种求取密码线性偏差上界的方法.该分析方法的思路是,首先对密码体制线性偏差进行严格的数学描述,分别给出密码线性偏差与轮函数F及S盒的线性偏差的数学关系;然后确定密码线性偏差的上界.利用该方法给出了32轮以内各轮的线性偏差上界.

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.