Cryptography – Particular algorithmic function encoding
Reexamination Certificate
2008-09-16
2011-10-04
Song, Hosuk (Department: 2435)
Cryptography
Particular algorithmic function encoding
C380S029000, C713S189000
Reexamination Certificate
active
08031866
ABSTRACT:
There is provided a highly secure cryptographic processing apparatus and method where an analysis difficulty is increased. In a Feistel type common key block encrypting process in which an SPN type F function having a nonlinear conversion section and a linear conversion section is repeatedly executed a plurality of rounds. The linear conversion process of an F function corresponding to each of the plurality of rounds is performed as a linear conversion process which employs an MDS (Maximum Distance Separable) matrix, and a linear conversion process is carried out which employs a different MDS matrix at least at each of consecutive odd number rounds and consecutive even number rounds. This structure makes it possible to increase the minimum number (a robustness index against a differential attack in common key block encryption) of the active S box in the entire encrypting function.
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Shibutani Kyoji
Shirai Taizo
Finnegan Henderson Farabow Garrett & Dunner
Song Hosuk
Sony Corporation
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