A computer receives, from a target device via a communication apparatus that is capable of accessing the target device, an issuance request for issuing key information unique to the target device. The computer generates the key information upon reception of the issuance request. The computer stores an address allocated to the communication apparatus and the key information in association with each other. The computer transmits the key information to the target device via the communication apparatus. The computer receives, from the communication apparatus, the key information and a registration request for registering a relay apparatus for relaying communication between the computer and the target device. The computer registers the communication apparatus as the relay apparatus when the address allocated to the communication apparatus and the address stored in association with the received key information match each other.