| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of surely executing cipher strength evaluation processing in a common key block cipher. SOLUTION: In a common key block cipher algorithm, vectors and matrixes are used to express an algorithm in a key schedule part by an equation, and nonlinear conversion output values and initial values in the matrix equation are erased by unitary conversion to obtain all linear relational expressions between round keys. In this method, linear relational expressions between round keys in a common key block cipher system can be all covered regardless of complication of a key schedule, and cipher strength evaluation of the common key block cipher system can be executed on the basis of derived linear relational expressions. COPYRIGHT: (C)2004,JPO
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