STORAGE MEDIUM, READ/WRITE APPARATUS, CARD SYSTEM, ENCRYPTION KEY UTILIZATION METHOD, STATION SERVICE SYSTEM, AND CARD ISSUING APPARATUS

摘要

PROBLEM TO BE SOLVED: To update a cryptographic key as required, e.g. periodically or in case of possibility of a decoded cryptographic key without using all cryptographic keys at random by updating the cryptographic key selected by a command sent from a reader/writer. SOLUTION: A reader/writer 6 stores old cryptographic keys that were used in the past and not in use at present and a cryptographic key that is currently in use. Furthermore, the reader/writer 6 transmits an update command to a passenger card 7 to allow the passenger card 7 to update its cryptographic key from an older cryptographic key to the cryptographic key used at present when the cryptographic key used by the passenger card 7 is the cryptographic key that was used in the past but not in use at present according to a response from the passenger card 7 as a result of communciation between the reader/ writer 6 and the passenger card 7, and the passenger card 7 updates the cryptographic key into the cryptographic key used at present in response to the command. Thus, the cryptographic key of the old passenger card 7 having been issued before is finally updated into the cryptographic key used at present.