Importance

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Abstract

In an IC card (electronic smart card) which can record or register a plurality of personal identification numbers (PINs), an externally entered personal identification number is collated with the personal identification numbers registered in the card, and when a coincidence occurs between the entered PIN and one of the registered PINs, a flag is set to indicate coincidence therebetween. At least two of the registered PINs share the same flag information. Each noncoincidence between an entered PIN and a registered PINs is counted. Response data indicating the unusability of the PIN is issued when the number of noncoincidences exceeds a predetermined value, while when the number of noncoincidences is below the predetermined value, response data indicating the PIN noncoincidence is issued. In counting the number of noncoincidences, the first count is made by a nonvolatile memory so that it may not be erased when a power supply is turned off and the subsequent counts are made by a nonvolatile memory.

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First Claim