A mobile communication terminal connected to the portable electronic device encodes a system serial number and an authentication key, generates an integration secrete key, and transmits the integration secrete key to an authentication center computer. The authentication center computer decodes the integration secrete key, performs authentication registration, encodes a temporary service approval key and a temporary integration authentication key, and transmits the temporary service approval key and the temporary integration authentication key to the mobile communication terminal. The mobile communication terminal decodes the temporary integration authentication key, obtains approval for the relay, and transmits the temporary service approval key to the portable electronic device. The portable electronic device decodes the temporary service approval key, performs authentication for utilizing a service, and applies the temporary service approval key to an application service.