研究了几种著名的分组密码体制的Ｓ盒所满足的代数方程的个数，如DES、AES、MARS、SERPENT等，分别计算出这几种分组密码的Ｓ盒从低次到高次的代数方程的个数，并把
计算结果和理论极小值进行了比较．此外，还针对一类对密码分析具有特别意义的不完全代数方程研究了Ｓ盒所满足的这类不完全代数方程的个数，通过这类方程的个数，可以看到它们的Ｓ盒与随机Ｓ盒的差别．

This paper focuses on the number of algebraic equations, which describe the S-boxes of several famous block ciphers such of DES, AES, MARS and SERPENT. We compute the number of these algebraic equations from low degree to high degree. A comparison between the number of these equations and the theoretical minimum value is presented. Moreover, this paper introduces a kind of incomplete algebraic equations which are especially important to cryptanalysis. By comparing the number of these incomplete equations with that of a random S-box, a difference is shown between the S-boxes of these block ciphers and a random S-box.