DEVICE AND METHOD FOR SEARCHING DATA CHANGE USED FOR INTENSITY EVALUATION OF CIPHER ALGORITHM, AND RECORDING MEDIUM RECORDING THE SAME METHOD

摘要

PROBLEM TO BE SOLVED: To enable the intensity evaluation of a cipher to performed by using difference with respect to a block cipher which has a recurring structure by providing a means, etc., which seeks generation probability of output difference in the said step due to the product of the generation probability of input difference and output difference of f-function processing part, the generation probability of the output of exclusive OR and the generation probability of the output difference of the preceding step. ;SOLUTION: This device and method are provided with a storing means which entirely stores the generation probability of the input difference and the output difference of the f-function processing part, a means which calculates the generation probability of the output of exclusive OR and a means which seeks the generation probability of the output difference of the said step for every step by the product of the generation probability of input difference and output difference of f-function processing part, the generation probability of the output of exclusive OR and the generation probability of the output difference of the preceding step. Therein, with respect to all of the input difference and the output difference by making the block cipher having Feistel structure as the object, the pair of the input difference and the output difference and the probability in a case that an output difference is generated from an input difference with the highest probability are calculated.;COPYRIGHT: (C)2001,JPO