| 摘要 |
PROBLEM TO BE SOLVED: To provide an IC card which is difficult to be used by a person pretending to be a user. SOLUTION: Ciphering authentication data are generated based on authentication fundamental data, including a random number part by using a ciphering rule, when a ciphering instruction is given by a ciphering authentication data generating means 5. The ciphering rule is varied according to the frequency of a given ciphering instruction. The ciphering authentication data are transmitted by a transmitting means 7. The ciphering authentication data transmitted from a second device B are received by a receiving means 9. A prohibiting instruction output means 11 judges whether or not the ciphering authentication data transmitted from the second device B match the ciphering authentication data generated, when the same frequency of the ciphering instruction is given to the ciphering authentication data-generating means of a first device A and outputs a prohibiting instruction to prohibit the transmission of the subject data to be transmitted, when a judging result is negative.
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