An identification information transmitter encrypts identification information for identifying a person or an object using an encryption key, transmits the encrypted identification information, and, after receiving another encryption key, switches the encryption key from the encryption key to the other encryption key. A server receives the encrypted identification information from the identification information transmitter, determines whether the encryption key is to be switched, and, if the encryption key is to be switched, generates the other encryption key. Another server authenticates the identification information that an identification information receiver receives from the identification information transmitter, and, if authentication is successful, acquires the other encryption key from the server, and transmits the other encryption key to the identification information receiver. The identification information receiver, when receiving the other encryption key from the second server, transmits the other encryption key to the identification information transmitter.