INFORMATION SYSTEM FOR DETECTING AND PREVENTING UNAUTHORIZED USE OF SHARED INFORMATION

摘要

PROBLEM TO BE SOLVED: To provide an information system capable of detecting and preventing unauthorized use of shared information and avoiding the multi-use of the shared information.

SOLUTION: When a natural random number source gives a natural random number and a random number combining part reads an ID and previously shared information K2 from a body to be authenticated so as to authenticate the body to be authenticated, the random number combining part combines random numbers from previously shared information and the natural random number, rewrites the previously shared information belonging to the body to be authenticated into a random number to thereby previously share the combined random number with the body to be authenticated as information K1 and K2 for the next authentication of the body to be authenticated. A causal string generating part orders the previously shared information and previously sharing information, associates them with an ID to store them, and thereby generates a causal string obtained by embodying the uniqueness of cause and effect. An unauthorized use detecting part monitors the uniqueness of the cause and effect of the causal string by comparing the uniqueness with a set of the ID read by the random number combining part and the previously shared information to thereby detect the unauthorized use of the previously shared information K1 and K2 about the ID and the previously shared information.

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