| 摘要 |
PURPOSE:To always perform required enciphering and decoding against any data input by performing the enciphering and decoding so that no data exceeding a prescribed integer value can be produced by using a modulo adder and modulo subtractor. CONSTITUTION:A modulo adder 302 inputs data M1, M2,... smaller than a specific integer value N and at the same time, data B, C1,... smaller than the integer value N from a delay buffer 303 and outputs the remainder X1 produced when the sum of M1 and B is divided by N, remainder X2 produced when the sum of M2 and C1 is divided by N,.... The remainders X1, X2,... are always smaller than the integer value N and a block cipher machine 301 inputs the output data X1, X2,... of the modulo adder 302 and an enciphering key 304, and outputs enciphered sentence data C1, C2,.... Therefore, enciphering and decoding can be performed in a CBC (Cipher Block Chaining) mode by using a block cipher machine and block decoding machine which respectively perform enciphering and decoding on numerals smaller than a specific integer value N.
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