| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-security encryption processing device and an encryption processing method with improved difficulty in analysis. SOLUTION: In a Feistel type common key block encryption wherein an SPN type F function having a non-linear transformation section and a linear transformation section is repeatedly executed a plurality of rounds, the linear transformation processing of the F function corresponding to each round is executed by applying a matrix satisfying comparatively gentle restriction conditions. This configuration improves resistance against a difference attack and a linear attack. Moreover, since the restriction is comparatively gentle, the number of matrix candidates which can be used is increased to increase the number of active S-boxes. That is, the minimum number of the active S-boxes as one of the encryption strength indexes can be increased, and highly secure encryption processing having improved resistance against an attack can be achieved. COPYRIGHT: (C)2007,JPO&INPIT
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