Abstract: A management server, a service server, and a plurality of user terminals are connected to each other via a network so as to be capable of transmitting and receiving data. The management server includes a user information storage unit that stores user identification information for identifying users belonging to a group, and an identification information notification processor that, each time a service to be provided to the users of the group is newly added, transmits the user identification information of the plurality of users belonging to the group to the service server by cryptographic communication, corresponding to the newly added service. The service server includes a service information storage unit for storing the user identification information of the plurality of users corresponding to the service, received from the identification information notification processor.