The Design And Analysis Of Substitution Boxes Of Block Cipher

Substitution 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 confusion of the whole cryptosystem. In particular, the S-box with high strength play a key role in strengthening the scurity of cipher with Feistel, SPN and IDEA. The research of S-box is of great value to both the designing of the iterative cryptosystem and the cryptanalysis whose core is nonlinear transform.The research will also assists lot in searching the function which meet the specific requirements faster than ever before. At present the designing of the block cipher mainly focuses on the nonlinear S-box design ,the choice of perutation 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 criteria mentioned above, a number of constructing methods were developed, such as random generate and test, construct with mathematic function.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 of S-box in block cipher , proposed the difinations on strong diffuse criteria, strong strict avalanche criteria and approximation of diffuse criteria , and clarified the relation between differential properties and nonlinearity, as well as balancity and diffuse criteria . Furhter, the thesis introduced the major designing ideas on sbox exisiting at present, base on which a further research on the classification and contruction of sbox was introduced. The thesis also analyzed the algebraic properties of the Camellia algorithm and Rijndael algorithm in the sbox and proposed relative improvements.