Data encrypting/decrypting conversion methods and apparatuses and data communication system adopting the same

A decrypting conversion apparatus in which at least one key and encrypted text data are inputted, the inputted encrypted text is divided into a first data and a second data, said first data and said second data are set as a first initial data L[1] and a second initial data R[1], a decrypting conversion processing is repeated at least twice using the same function to receive data L[N] and data R[N] and output data L[N+1] and data R[N+1], respectively, wherein N is a natural number, and a combination of the two output data from a final stage of the decrypting conversion processing is provided as plain text data, comprising:

• cyclic shift processing means for performing a cyclic shift processing based on a shift number determined by data for determining a shift number selecting sequence, said shift number being independent from the plain text data;
• and
• said cyclic shift processing means including at least two different fixed cyclic shift processing means each for performing cyclic shift by a fixed number of bits leftward or alternatively rightward, cyclic shift processing selecting means for selecting said fixed cyclic shift processing means, and cyclic shift processing sequence determining means for determining a selecting sequence for said cyclic shift processing selecting means on the basis of said data for determining a shift number selecting sequence;
• decrypting conversion processing means for performing at least once for said data L[N] a conversion processing by using said key and a cyclic shift processing using said cyclic shift processing means, respectively, to thereby generate data X, and arithmetically operating said data R[N] and said data X to obtain a value for said data L[N+1] and set said data L[N] for said data R[N+1].

An encrypting conversion method of generating encrypted text data, comprising in combination the steps of:

• inputting at least one key and plain text data, dividing the inputted plain text into a first data and a second data;
• setting said first data and said second data as a first initial data L[1] and a second initial data R[1];
• repeating at least twice an encrypting conversion processing using the same function to receive data L[N] and data R[N] and output data L[N+1] and data R[N+1], respectively, where N is a natural number;
• providing a combination of the two output data from a final stage of the encrypting conversion processing is provided as an encrypted text;
• performing a cyclic shift processing based on a shift number by data for determining a shift number, said shift number being independent from the plain text data;
• performing at least once for said data L[N], a conversion processing by using said key and a cyclic shift processing using said cyclic shift processing performing step, respectively, to thereby generate data X;
• arithmetically operating said data R[N] and said data X to obtain a value for said data L[N+1] and set said data L[N] for said data R[N+1];
• and
• wherein the data for determining the shift number is made to differ between at least two encrypting conversion processings.

A decrypting conversion method of generating plain text data, comprising in combination the steps of:

• inputting at least one key and encrypted text data, dividing the inputted encrypted text into a first data and a second data;
• setting said first data and said second data as a first initial data L[1] and a second initial data R[1];
• repeating at least twice a decrypting conversion processing using the same function to receive data L[N] and data R[N] and output data L[N+1] and data R[N+1], respectively, where N is a natural number;
• providing a combination of the two output data from a final stage of the decrypting conversion processing as plain text;
• performing a cyclic shift processing based on a shift number by data for determining a shift number, said shift number being independent from the plain text data;
• performing at least once for said data L [N], a conversion processing by using said key and a cyclic shift processing using said cyclic shift processing performing step, respectively, to thereby generate data X;
• and
• arithmetically operating said data R[N] and said data X to obtain a value for said data L[N+1] and set said data L[N] for said data R[N+1];
• wherein the data for determining the shift number is made to differ between at least two decrypting conversion processings.

A computer program for generating encrypted text data in which at least one key and plain text data are inputted, the inputted plain text is divided into a first data and a second data, said first data and said second data are set as a first initial data L[1] and a second initial data R[1], an encrypting conversion processing is repeated at least twice using the same function to receive data L[N] and data R[N] and output data L[N+1] and data R[N+1], respectively, wherein N is a natural number, and a combination of the two output data from a final stage of the encrypting conversion processing is provided as an encrypted text, the computer program stored on a computer-readable medium and comprising:

• instructions for performing a cyclic shift processing for performing a cyclic shift processing based on a shift number determined by data for determining a shift number, said shift number being independent from the plain text data;
• instructions for performing at least once for said date L[N] an encrypting conversion processing by using said key and a cyclic shift processing using said cyclic shift processing means, respectively, to thereby generate data X, and arithmetically operating said data R[N] and said data X to obtain a value for said data L[N+1] and set said data L[N] for said data R[N+1];
• and
• wherein the data for determining the shift number is made to differ between at least two encrypting conversion processings.

A computer program for generating plain text data in which at least one key and encrypted text data are inputted, the inputted encrypted text is divided into a first data and a second data, said first data and said second data are set as a first initial data L[1] and a second initial data R[1], a decrypting conversion processing is repeated at least twice using the same function to receive data L[N] and data R[N] and output data L[N+1] and data R[N+1], respectively, wherein N is a natural number, and a combination of the two output data from a final stage of the decrypting conversion processing is provided as plain text, the computer program stored on a computer-readable medium and comprising:

• instructions for performing a cyclic shift processing for performing a cyclic shift processing based on a shift number determined by data for determining a shift number, said shift number being independent from the plain text data;
• instructions for performing at least once for said data L[N] a decrypting conversion processing by using said key and a cyclic shift processing using said cyclic shift processing means, respectively, to thereby generate data X, and arithmetically operating said data R[N] and said data X to obtain a value for said data L[N+1] and set said data L[N] for said data R[N+1];
• and
• wherein the data for determining the shift number is made to differ between at least two decrypting conversion processings.

An encrypting conversion apparatus for inputting at least one cipher key and plain text data and outputting cipher text data, the encrypting conversion apparatus comprising:

• a plurality of stages of encrypting conversion means for performing a first conversion for substituting different data for at least the plain text data and a second conversion for rearranging bits of the data,
• wherein said encrypting conversion means executes either an exclusive logical sum operation or ah addition operation of input data and first data generated from the cipher key, thereafter executes said first conversion and said second conversion, thereafter executes either an exclusive logical sum operation or an addition operation of the input data and second data generated from the cipher key, and thereafter executes said first conversion;
• and
• wherein encrypting conversion processing performed by said encrypting conversion means is repeated at least twice using the same function;
• wherein the data for determining the shift number is made to differ between at least two encrypting conversion processings by said encrypting conversion processing means.

A decrypting conversion apparatus for inputting at least one cipher key and cipher text data and outputting plain text data, the decrypting conversion apparatus comprising:

• a plurality of stages of decrypting conversion means for performing a first conversion for substituting different data for at least the cipher text data and a second conversion for rearranging bits of the data,
• wherein said decrypting conversion means executes either an exclusive logical sum operation or an addition operation of input data and first data generated from the cipher key, thereafter executes said first conversion and said second conversion, thereafter executes either an exclusive logical sum operation or an addition operation of the input data and second data generated from the cipher key, and thereafter executes said first conversion;
• and
• wherein decrypting conversion processing performed by said decrypting conversion means is repeated at least twice using the same function;
• wherein the data for determining the shift number is made to differ between at least two decrypting conversion processings by said decrypting conversion processing means.

An encrypting conversion apparatus in which at least one key and plain text data are inputted, the inputted plain text is divided into a first data and a second data, said first data and said second data are set as a first initial data L[1] and a second initial data R[1], an encrypting conversion processing is repeated at least twice using the same function to receive data L[N] and data R[N] and output data L[N+1] and data R[N+1], respectively, wherein N is a natural number, and a combination of the two output data from a final stage of the encrypting conversion processing is provided as an encrypted text, comprising:

• a cyclic shift processor, which performs a cyclic shift processing based on a shift number determined by data for determining a shift number selecting sequence, said shift number being independent from the plain text data,
• said cyclic shift processor including at least two different fixed cyclic shift processors, each of which performs cyclic shift by a fixed number of bits leftward or alternatively rightward, a cyclic shift processing selector, which selects said fixed cyclic shift processors, and a cyclic shift processing sequence determining device, which determines a selecting sequence for said cyclic shift processing selector on the basis of said data for determining a shift number selecting sequence;
• and
• an encrypting conversion processor, which performs at least once for said data L[N] a conversion processing by using said key and a cyclic shift processing using said cyclic shift processor, respectively, to thereby generate data X, and arithmetically operating said data R[N] and said data X to obtain a value for said data L[N+1] and set said data L[N] for said data R[N+1].