| 摘要 |
PURPOSE:To prevent a leakage of secrecy authorizing information to a third person by making information a different number each time of authorizing action even when it is obtained on the communication line between terminals in order that the terminal is recognized as a valid one. CONSTITUTION:In the random number generation part 33 of an IC card terminal 1, generates random numbers R that differ every when they are generated, a cipher device 34 enciphers the random number R with secrecy authorizing information R1 for ciphering key, and a number X is thus generated. A decoder 45 decodes the number X with secrecy authorizing information S2 for decoding key in order to generate a number Y, and an encoder 44 enciphers common information C2 with the number Y for ciphering key in order to generate a number Z. A decoder 35 decodes the number Z with the random number R for decoding key, and generates a number U. In case the number U and the common information C1 do not coincide with each other, the IC card terminal 1 does not authorize an IC card 2 as valid. If the bits of secrecy authorizing information S2 and S1 differ from each other, the number Y and that R must also differ from each other hence the result of the enciphering of common information is decoded with the number R for decoding key, the result will not coincide with the common information C1. |
