Patent ID: 6606385
Filing Date: 2003-08-12
Classification: G10H,H04L

Abstract:
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: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; encrypting 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].