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CRYPTOGRAPHIC PROCESSING APPARATUS, CRYPTOGRAPHIC PROCESSING METHOD, AND STORAGE MEDIUM STORING CRYPTOGRAPHIC PROCESSING PROGRAM FOR REALIZING HIGH-SPEED CRYPTOGRAPHIC PROCESSING WITHOUT IMPAIRING SECURITY

  • US 6,570,989 B1
  • Filed: 04/21/1999
  • Issued: 05/27/2003
  • Est. Priority Date: 04/27/1998
  • Status: Expired due to Term
First Claim
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1. An encryption or decryption apparatus including data conversion means for performing a data conversion on input data using a plurality of sets of substitution data to generate output data,wherein the encryption or decryption apparatus uses a cipher that corresponds to a conventional cipher which uses a F function, the data conversion means corresponds to a device for performing the F function of the conventional cipher, and the device for performing the F function of the conventional cipher (a) stores (2{circumflex over ( )}N)×

  • M sets of substitution data that are each (N×

    M) bits long, (b) acquires input data of (N×

    M) bits that is subjected to a data conversion, (c) generates M sets of N-bit subdata from the input data of (N×

    M) bits, (d) receives the M sets of N-bit subdata, specifies M sets of (N×

    M)-bit substitution data from the (2{circumflex over ( )}N)×

    M sets of substitution data, and outputs the M sets of (N×

    M)-bit substitution data, and (e) generates output data of (N×

    M) bits based on the M sets of (N×

    M)-bit substitution data, where N is an integer no less than 2 and M is an integer no less than 2, the data conversion means comprising;

    storing means for storing (2{circumflex over ( )}M) sets of substitution data that each have a predetermined number of bits, the predetermined number being equal to or less than (N×

    M), wherein the total size of substitution data stored in the storing means is no greater than 1/M the total size of substitution data stored in the device for performing the F function of the conventional cipher;

    acquiring means for acquiring input data that is subjected to a data conversion, the input data being (N×

    M) bits long;

    subdata generating means for generating at least one set of N-bit subdata from the input data acquired by the acquiring means;

    substituting means for receiving the at least one set of subdata generated by the subdata generating means, specifying one of the (2{circumflex over ( )}N) sets of substitution data in the storing means for each of the at least one set of subdata, and outputting at least one set of substitution data specified respectively for the at least one set of subdata;

    fixed conversion performing means for performing a plurality of different fixed conversions on the at least one set of substitution data outputted from the substituting means, to generate M sets of converted data that each have the predetermined number of bits; and

    output data generating means for generating output data that is (N×

    M) bits long, based on the M sets of converted data generated by the fixed conversion performing means.

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