PROBLEM TO BE SOLVED: To provide a prepaid card system high in recurity and capable of reusing a prepaid card and to provide a prepaid card reissuing method. ;SOLUTION: This recording device 11 ciphers amount information for plural times in the prepaid card and records them. At the time of ciphering, the recording device 11 uses a password key for reading in amount information for the first time and sequentially uses plural password keys for second and subsequent amount information. A reader 13 has a password key for reading, decodes amount information in the card of a use object with the reading password key and updates it, in accordance with a payment amount. The reader 13 ciphers updated amount information with the reading password key and stores it in the card. The card whose amount information is used up is processed in a recycle card issuing machine 15. The recycle card issuing machine 15 has a reading password key and plural decoding keys. It decodes amount information, which is to be used next in the card of the processing object with the appropriate decoding key, ciphers it with the reading password key and stores it in the card.;COPYRIGHT: (C)1999,JPO
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