Facilitate configuration of authentication information for a service provided over IP network when there is no shared authentication information between IoT device and service provider device for a service used by IoT device, an intermediary device capable of authenticating legitimate access mediates between devices. An example: a cipher key CK stored in intermediary device and IoT device, as a result of SIM authentication of the SIM of the IoT device, is used as master key for services used by IoT device. By generating unique application key for a service used by IoT device on the intermediary device and IoT device on the basis of master key, and sending it to service provider apparatus from intermediary device by secure connection, common keys are set as authentication information to IoT device and service provider apparatus. A SIM authentication process for generating cipher key can suppress SQN attack based on a bad request.