PROBLEM TO BE SOLVED: To prevent an identity provider from providing a service provider with identity information which a user himself does not desire to disclose and which has reliability exceeding a request of the service provider. SOLUTION: An ID bridge service system includes a selector and a request means. The selector manages: types and reliability of identity information which is necessary for an application service system to provide services; and types and reliability of identity information which is managed by a plurality of authentication service systems, and when receiving an authentication request from the application service system, the selector selects the authentication service system which manages the identity information corresponding to the identity information necessary for the application service system to provide service, from among the plurality of authentication service systems. The request device requests authentication to the selected authentication service system. COPYRIGHT: (C)2011,JPO&INPIT