ENCRYPTED DATA TRANSMITTING APPARATUS, ENCRYPTION KEY UPDATING METHOD, ELECTRONIC DEVICE, PROGRAM AND RECORDING MEDIUM

摘要

PROBLEM TO BE SOLVED: To solve a problem that a receiver can not rightly decrypt encrypted data if an encryption key is updated just after a transmitter transmits the encryption key to the receiver. SOLUTION: An encryption key updating means 306 is provided, which judges whether next encrypted data are transmitted within a first predetermined time from the transmission completion of encrypted data and whether authentication and key exchange is performed after the lapse of a second predetermined time shorter than the first predetermined time, updates an encryption key in the end of the first predetermined time if the next encrypted data are not transmitted within the first predetermined time and the authentication and key exchange is not performed after the lapse of the second predetermined time, and updates the encryption key in the case of the authentication and key exchange if the next encrypted data are not transmitted within the first predetermined time and the authentication and key exchange is performed after the lapse of the second predetermined time. A counter 310 for the first and second predetermined times is then reset when completing the transmission of the encrypted data and before transmitting the updated encryption key if the authentication and key exchange is performed after the lapse of the second predetermined time. COPYRIGHT: (C)2007,JPO&INPIT