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

Abstract

Encrypting/decrypting conversion method and apparatus capable of controlling dynamically cyclic shift independent of data to undergo encrypting/decrypting conversion includes two or more different fixed circulating shift processing means for shifting cyclically the data by a fixed bit number leftward or rightward, a cyclic shift processing selecting means for selecting fixed cyclic shift processing means. The selecting sequence determined by the cyclic shift processing means is determined on the basis of data for determining the shift number selecting sequence.

What is claimed is:  
     
         1 . An encrypting conversion apparatus which receives as inputs thereto at least one key and plain-text data to thereby output encrypted text data, comprising: 
 cyclic shift processing means for determining a shift number on the basis of data for determining a shift number selecting sequence;    means for dividing inputted plain-text data into first data and second data and setting said first data as data L[1] while setting said second data as data R[1];    at least one stage of encrypting conversion processing means for receiving as inputs thereto data L[N] and R[N] to thereby output data L[N+1] and data R[N+1], said encrypting conversion processing means being so arranged as to perform at least once for said data L[N] a conversion processing by using said key and a cyclic shift processing by means of said cyclic shift processing means, respectively, to thereby generate data X, wherein a value derived from arithmetic operation of said data R[N] and said data X is set as said data L[N+1] while said data L[N] being set as said data R[N+1], and    means for outputting a combination of two output data from a final stage of said encrypting conversion processing means as an encrypted text.    
     
     
         2 . An encrypting conversion apparatus according to    claim 1   , 
 wherein the data for determining said shift number selecting sequence is made to differ between at least two of said encrypting conversion processing means.    
     
     
         3 . An encrypting conversion apparatus according to    claim 1   , 
 wherein said shift number is made to differ between at least two of said cyclic shift processing means.    
     
     
         4 . An encrypting conversion apparatus which receives as inputs thereto at least one key and plain-text data to thereby output encrypted text data, comprising: 
 cyclic shift processing means for determining a shift number on the basis of data for determining a shift number selecting sequence;    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 data for determining said shift number selecting sequence;    means for dividing inputted plain-text data into first data and second data and setting said first data as data L[1] while setting said second data as data R[1];    at least one stage of encrypting conversion processing means for receiving as inputs thereto data L[N] and R[N] to thereby output data L[N+1] and data R[N+1], said encrypting conversion means being so arranged as to perform at least once for said data L[N] a conversion processing by using said key and a cyclic shift processing by means of said cyclic shift processing means, respectively, to thereby generate data X, wherein a value derived from arithmetic operation of said data R[N] and said data X is set as said data L[N+1] while said data L[N] being set as said data R[N+1], and    means for outputting a combination of two output data from a final stage of said encrypting conversion processing means as an encrypted text.    
     
     
         5 . An encrypting conversion apparatus according to    claim 4   , 
 said cyclic shift sequence determining means being so arranged as to select at least two of said fixed cyclic shift processing means in accordance with the sequence determined by said cyclic shift sequence determining means;    said cyclic shift processing sequence determining means being so arranged as to determine the cyclic shift processing sequence which differs from one to another stage of said encrypting conversion processing means in response to input values of bit strings of the data, respectively, for thereby determining said shift number selecting sequence, said input values of said bit strings differing from one to another stage of said encrypting conversion processing means; and    said encrypting conversion processing means being so arranged as to perform block-based encrypting conversions which differ from one to another stage of said encrypting conversion processing means.    
     
     
         6 . An encrypting conversion apparatus according to    claim 1   , 
 wherein said data for determining said shift number selecting sequence is generated on the basis of said key.    
     
     
         7 . An encrypting conversion apparatus according to    claim 4   , 
 wherein said fixed cyclic shift processing means is constituted by a wired logic circuit.    
     
     
         8 . An encrypting conversion apparatus according to    claim 4   , 
 wherein said cyclic shift processing selecting means is constituted by a multiplexer.    
     
     
         9 . An encrypting conversion apparatus according to    claim 4   , 
 wherein said cyclic shift processing sequence determining means is implemented by a cyclic shift processing sequence generating circuit which makes internal status transition in response to a synchronizing signal by using said cyclic shift determining data as initial values of internal statuses and input signals for thereby outputting control input signals for said cyclic shift processing selecting means.    
     
     
         10 . An encrypting conversion apparatus according to    claim 4   , 
 wherein said fixed cyclic shift processing means, said cyclic shift processing selecting means and said cyclic shift processing sequence determining means are each implemented softwarewise.    
     
     
         11 . A decrypting conversion apparatus which receives as inputs thereto at least one key and encrypted text to thereby output plain-text data, comprising: 
 cyclic shift processing means for determining a shift number on the basis of data for determining a shift number selecting sequence;    means for dividing inputted encrypted text data into first data and second data and setting said first data as data L[1] while setting said second data as data R[1];    at least one stage of decrypting conversion means for receiving as inputs thereto data L[N] and R[N] to thereby output data L[N+1] and data R[N+1], said decrypting conversion means being so arranged as to perform at least once for said data R[N] a conversion processing by using said key and a cyclic shift processing by means of said cyclic shift processing means, respectively, to thereby generate data X, wherein a value derived from arithmetic operation of said data L[N] and said data X is set as said data R[N+1] while said data R[N] being set as said data L[N+1], and    means for outputting a combination of two output data from a final stage of said decrypting conversion means as a plain-text.    
     
     
         12 . A decrypting conversion apparatus according to    claim 11   , 
 wherein said data for determining said shift number selecting sequence is made to differ between at least two of said decrypting conversion processing means.    
     
     
         13 . A decrypting conversion apparatus according to    claim 11   , 
 wherein said shift number is made to differ between at least two of said cyclic shift processing means.    
     
     
         14 . A decrypting conversion apparatus which receives as inputs thereto at least one key and encrypted text data to thereby output plain-text data, comprising: 
 cyclic shift processing means for determining a shift number on the basis of data for determining a shift number selecting sequence;    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 data for determining said shift number selecting sequence;    means for dividing inputted encrypted text data into first data and second data and setting said first data as data L[1] while setting said second data as data R[1];    at least one stage of decrypting conversion means for receiving as inputs thereto data L[N] and R[N] to thereby output data L[N+1] and data R[N+1], said decrypting conversion means being so arranged as to perform at least once for said data R[N] a conversion processing by using said key and a cyclic shift processing by means of said cyclic shift processing means, respectively, to thereby generate data X, wherein a value derived from arithmetic operation of said data L[N] and said data X is set as said data R[N+1] while said data R[N] being set as said data L[N+1], and    means for outputting a combination of two output data from final stage of said decrypting conversion means as a plain-text.    
     
     
         15 . A decrypting conversion apparatus according to    claim 14   , 
 said cyclic shift sequence determining means being so arranged as to select at least two of said fixed cyclic shift processing means in accordance with the sequence determined by said cyclic shift sequence determining means;    said cyclic shift processing sequence determining means being so arranged as to determine the cyclic shift processing sequence which differs from one to another stage of said decrypting conversion processing means in response to input values of bit strings of the data, respectively, for thereby determining said shift number selecting sequence, said input values of said bit strings differing from one to another stage of said decrypting conversion processing means; and    said decrypting conversion processing means being so arranged as to perform block-based decrypting conversion processings which-differ from one to another stage of said decrypting conversion processing means.    
     
     
         16 . A decrypting conversion apparatus according to    claim 11   , 
 wherein said data for determining said shift number selecting sequence is generated on the basis of said key.    
     
     
         17 . A decrypting conversion apparatus according to    claim 14   , 
 wherein said cyclic shift processing sequence determining means is implemented by a cyclic shift processing sequence generating circuit which makes internal status transit in response to a synchronizing signal by using said cyclic shift determining data as initial values of internal statuses and input signals for thereby outputting a control input signal for said cyclic shift processing selecting means.    
     
     
         18 . An encrypting conversion method of generating encrypted text data on the basis of at least one key and plain-text data as inputted, comprising the steps of: 
 performing a cyclic shift processing for determining a shift number on the basis of data for determining a shift number selecting sequence;    dividing inputted plain-text data into first data and second data and setting said first data as data L[1] while setting said second data as data R[1];    performing at least one encrypting conversion processing for data L[N] and R[N] inputted, to thereby output data L[N+1] and data R[N+1], said encrypting conversion processing being so arranged as to perform at least once for said data L[N] a conversion processing by using said key and a cyclic shift processing, respectively, to thereby generate data X, wherein a value derived from arithmetic operation of said data R[N] and said data X is set as said data L[N+1] while said data L[N] being set as said data R[N+1], and    outputting a combination of two output data from final stage of said encrypting conversion processing as an encrypted text.    
     
     
         19 . A decrypting conversion method of generating plain-text data on the basis of at least one key and encrypted text data received as inputs, comprising the steps of: 
 performing a cyclic shift processing for determining a shift number on the basis of data for determining a shift number selecting sequence;    dividing inputted encrypted text data into first data and second data and setting said first data as data L[1] while setting said second data as data R[1];    performing at least one decrypting conversion processing for data L[N] and R[N] received as input to thereby output data L[N+1] and data R[N+1], said decrypting conversion processing being so arranged as to perform at least once for said data R[N] a conversion processing by using said key and a cyclic shift processing, respectively, to thereby generate data X, wherein a value derived from arithmetic operation of said data L[N] and said data X is set as said data R[N+1] while said data R[N] being set as said data L[N+1], and    outputting a combination of two output data from final stage of said decrypting conversion processing as a plain-text.    
     
     
         20 . A data communication system in which a key encrypting key is previously set to be shared between two apparatuses A and B capable of communicating with each other, 
 said apparatus A generating a data key and then sending to said apparatus B data key encrypted with a key encrypting key, and    said apparatus B restoring original data by decrypting an encrypted text of the data key,    wherein encrypted text derived by encrypting plain-text data with said data key is transferred between said apparatus A and said apparatus B, for allowing encrypted communication to be performed between said apparatuses A and B to thereby derive the plain-text data by decrypting the received encrypted text with the data key.    
     
     
         21 . A data communication system according to    claim 20   , 
 wherein said apparatus A includes means for preventing plain-text data from being sent externally of said apparatus A without performing encrypting conversion for said plain-text data.    
     
     
         22 . A data communication system according to    claim 20   , 
 wherein said apparatus B includes means for preventing plain-text data derived through decrypting conversion of encrypted text data from being transmitted externally of said apparatus B.    
     
     
         23 . A data communication system according to    claim 20   , 
 wherein said apparatus A or said apparatus B is arranged to communicate with another apparatus C, further comprising:    means for allowing said apparatus C to check whether or not data sent to said apparatus C from said apparatus A or said apparatus B has undergone encrypting conversion; and    means for sending a signal to other apparatus D indicating that said data has not undergone encrypting conversion processing unless said data has undergone the encrypting conversion processing.    
     
     
         24 . A data communication system according to    claim 23   , 
 wherein when said apparatus D receives a signal indicating that said data has not undergone encrypting conversion, data to be sent from said apparatus D to said apparatus A is limited.    
     
     
         25 . A data communication system according to    claim 20   , 
 said apparatus A or said apparatus B being so arranged to be capable-of communicating with another apparatus E,    wherein said apparatus E is so arranged as to send to said apparatus A an encrypted text #1 resulting from encryption of a plain-text data in accordance with an encryption scheme #1 to thereby obtain original plain-text data, whereon said plain-text data is again encrypted in accordance with an encryption scheme #2 differing from said encryption scheme #1 to thereby derive an encrypted text #2, whereon said encrypted text #2 is sent to said apparatus B.    
     
     
         26 . A computer program for generating encrypted text data on the basis of at least one key and plain-text data as inputted, the computer program stored on a computer-readable medium comprising: 
 instructions for performing a cyclic shift processing for determining a shift number on the basis of data for determining a shift number selecting sequence;    instructions for dividing inputted plain-text data into first data and second data and setting said first data as data L[1] while setting said second data as data R[1];    instructions for performing at least one encrypting conversion processing for data L[N] and R[N] inputted, to thereby output data L[N+1] and data R[N+1], said encrypting conversion processing being so arranged as to perform at least once for said data L[N] a conversion processing by using said key and a cyclic shift processing, respectively, to thereby generate data X, wherein a value derived from arithmetic operation of said data R[N] and said data X is set as said data L[N+1] while said data L[N] being set as said data R[N+1], and    instructions for outputting a combination of two output data from final stage of said encrypting conversion processing as an encrypted text.    
     
     
         27 . A computer program for generating plain-text data on the basis of at least one key and encrypted text data received as inputs, the computer program stored on a computer-readable medium comprising: 
 instructions for performing a cyclic shift processing for determining a shift number on the basis of data for determining a shift number selecting sequence;    instructions for dividing inputted encrypted text data into first data and second data and setting said first data as data L[1] while setting said second data as data R[1];    instructions for performing at least one decrypting conversion processing for data L[N] and R[N] received as input to thereby output data L[N+1] and data R[N+1], said decrypting conversion processing being so arranged as to perform at least once for said data R[N] a conversion processing by using said key and a cyclic shift processing, respectively, to thereby generate data X, wherein a value derived from arithmetic operation of said data L[N] and said data X is set as said data R[N+1] while said data R[N] being set as said data L[N+1], and instructions for outputting a combination of two output data from final stage of said decrypting conversion processing as a plain-text.