| 摘要 |
PURPOSE: To provide a product encoding device which can make capacity of a ROM realizing a S box small. CONSTITUTION: A selector 101 selects a sentence not coded, inputted from an input terminal 113 or one side of output of a register 105 in accordance with an output control signal of a control circuit 106. A transposition circuit 102 performs transposition for an input of 64 bits supplied from the selector 101, and supplies the obtained 64 bits transposition result to a selector 103. In S boxes 1041 -1048 , replacement specified by a coding key of k'bits supplied from a storage circuit 107 for a given 8 bits input is performed, and the replacement result is outputted. After the control circuit 106 performs transposition for an input sentence one time by controlling the selectors 101, 103, the register 105 and the storage circuit 107, and repeats performing replacement using the S boxes 1041 -1048 two times successively.
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