Cryptographic Properties Of The Block Cipher S-boxes

S-box first appeared in the Lucifer algorithm and became popular with the application of the DES. S-box is the only nonlinear component in many cryptosystem.Therefore, the strength of the S-box determines the strength of the whole cryptosystem, and its efficiency determines the efficiency of the whole cryptosystem. Specially, the S-box with high strength plays a role in strengthening the scurity of the cipher with Feistel, SPN and IDEA.At present the designing of the block cipher mainly focuses on the nonlinear S-box design, the choice of permutation method and the better key schedule.The design and the construction of the S-box mainly involves its design criteria and constructing method.The major designing criteria are: nonlinearity, differential properties, algebraic degree, distribution of term, diffuse criteria, balancity and Correlation Immunity..Based on the tracing of AES scheme in the U.S.A and the NESSIE scheme in Europe, this thesis made a deep and comprehensive research on the designing criteria and their relationship of S-box in block cipher.The thesis introduced the major designing ideas on S-box exisiting at present,and clarified the relation between differential properties and nonlinearity,as well as balancity and diffuse criteria. Further, The thesis analyze the cryptographic properties of the Serpent algorithm and MISTY1 algorithm, and give the overlap distributing periodsand the detailed bool expression of the output bit of their S-boxes. Based on the bool Walsh cycle spectrum, the thesis analyze the cryptographic properties of the Camellia S-boxes, and give detailedly the overlap distribution period of the first S-box, and the autocorrelation function value and the bool function items of the four S-boxes of the Camellia algorithm.