A program when executed by a computer for controlling a registration server configured to be connected to a first network, causing the computer to execute: receiving user identification information; receiving device identification information from a communication terminal connected to a second network different from the first network, the device identification information being for identifying, on the second network, an information device connected to the second network; transmitting the received user identification information to a management server connected to the first network; receiving, from the management server, authentication information transmitted from the management server as a response to the transmitted user identification information; generating registration information which has a format in which the authentication information is allowed to be registered in the information device, the registration information including the authentication information and the device identification information; and transmitting the generated registration information to the communication terminal.