EVALUATION METHOD FOR STRENGTH OF CIPHER ALGORITHM AND STRENGTH EVALUATION DEVICE

摘要

PURPOSE: To provide an evaluation method for strength of cipher algorithm and a strength evaluation device which are adaptable to an involution type cipher such as FEAL and the like which have more search calculation quantity than DES in a practical time. ;CONSTITUTION: This device has an initial value setting means 110 setting an initial value when the maximum deviation rate of (n) stages linear expression of a cipher algorithm is searched, a search candidate extracting means 120 extracting a search pattern candidate conforming to a restriction condition, a best expression search means 130 searching n stages linear expression of the maximum deviation rate for search pattern candidate assemblage, a non- cipher information quantity calculating means 140 calculating non-cipher information quantity required for performing cipher decoding by a linear decoding method from the maximum deviation rate, and an output means 150 outputting non-cipher information quantity.;COPYRIGHT: (C)1996,JPO