| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that a computing quantity becomes huge although the searching probability of a code key is improved if the repeation number T of deformation coding, the number M of initial values and the number of sheets L of a search table are increased. SOLUTION: This device is provided with a pre-processing part 6 which generates a cipher key from an initial code sentence or a code sentence of an assumed plaintext by referring to a reduction table of each group generated by a reduction table creating part 4 and repeatedly performs coding processing of the assumed plaintext by using the cipher key to generate a coded sentence to be retrieved. Thus, the searching range of a key can be narrowed, thereby the cipher key can be searched by a small computing quantity.
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