Authentication method, communication apparatus, and relay apparatus

摘要

A certifying method comprises: a) a transmission step by a relay device for transmitting time information corresponding to the clocking present time of the relay device to a communication device when the communication device starts communication with another device through the relay device, b) a correction step by the communication device for correcting the clocking present time of the communication device on the basis of the time information transmitted in the transmission step and received by the communication device, c) a relay step by the relay device for relaying a certificate information with a certified validity period, the certified information is transmitted from the other communication device to the communication device, and certifying the authentication of other communication device or the other communication device user, d) a judgment step by the communication device for judging whether the present time is within the validity period specified in the certificate information relayed in the relay step and received on the basis of the present time of the concerned communication device corrected in the correction step, and e) a certificate step for judging the authentication of the other communication device or the other communication device user by the communication device through the judgment result in the judgment step and the certificate information.