一种改善双射S盒密码特性的有效算法

S盒是许多密码算法中的惟一非线性部件，它的密码强度决定了整个密码算法的安全强度．利用基因算法可以构造出密码特性良好的S盒，实践证明，若能在基因算法的中间过程对子S盒的密码特性作局部优化，将会使算法更加有效．William Millan曾给出一个改善双射S盒的非线性度的算法．而差分均匀性也是衡量S盒密码特性的一个重要指标，研究了如何利用差分矩阵来改善差分均匀性，并给出了一个实用的算法，它能同时改善一个随机选取的双射S盒的非线性度和差分均匀性．

An Effective Algorithm for Improving Cryptographic Properties of Bijective S-Boxes

S-boxes are the only nonlinear component in many cryptographic algorithms, which decides the secutity strength of the whole algorithm. S-boxes with good cryptographic properties can be constructed by genetic algorithm, and it is proved in practice that optimizing cryptographic propertie of S-boxes in the middle procedure of algorithm can make the algorithm more effective. Difference uniformity is also an important aspect to weigh S-boxes. How to improve difference uniformity with difference matrix is considered. And a practical algorithm is given, which can improve nonlinearity and difference uniformity of a randomly chosen bijective S-box simultaneously.