Cryptography – Communication system using cryptography – Time segment interchange
Reexamination Certificate
2004-09-28
2008-10-07
Song, Hosuk (Department: 2135)
Cryptography
Communication system using cryptography
Time segment interchange
C380S028000
Reexamination Certificate
active
07433470
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.
REFERENCES:
patent: 4078152 (1978-03-01), Tuckerman, III
patent: 7194090 (2007-03-01), Muratani et al.
Shibutani Kyoji
Shirai Taizo
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Song Hosuk
Sony Corporation
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