Patent ID: 8396210

Claim:
A cryptographic processing apparatus that executes Feistel type common key block cipher processing, the apparatus comprising: a data processing unit that executes round operations for a plurality of rounds by selectively applying at least two or more types of different F-functions as round functions; and a memory having stored therein a plurality of F-function correspondence tables, each corresponding to one of the at least two or more types of different F-functions, in which input values and output values are associated with each other, wherein the data processing unit is configured to: in accordance with a prescribed cryptographic processing sequence, acquire addresses for accessing F-function correspondence tables corresponding to F-functions to be applied in respective rounds, access the memory by applying the acquired addresses to read the F-function correspondence tables corresponding to the F-functions for the respective rounds, and acquire, on the basis of reference to the tables, output values for input values to obtain data transformation results in accordance with the respective F-functions, and execute cryptographic processing in accordance with a Feistel structure or extended Feistel structure having a diffusion-matrix switching mechanism that selectively applies at least two or more different F-functions in which at least two or more different matrices are set as transformation matrices to be applied to linear transformation processes within the F-functions for the respective rounds.