Authentication intermediary server, program, authentication system and selection method

A program that makes a computer function as an authentication intermediary server for selecting an authentication server authenticating a user of a terminal device when the terminal device is going to receive service from a service providing server, wherein:

• the program makes the computer function as a control part and a storage part that stores service providing server request information, with the service providing server request information specifying a service providing server ID and a requested condition requested in authentication by a service providing server corresponding to the service providing server ID;
• and
• the program makes the control part perform:
• processing, in which, when an information acquisition request specifying a service providing server ID is received from the service providing server, a requested condition corresponding to the service providing server ID specified by the information acquisition request is acquired from the service providing server request information, and the authentication server satisfying the acquired requested condition is selected;
• and
• processing, in which information specifying the selected authentication server is notified to the service providing server.

An authentication system comprising:

• a terminal device;
• a service providing server that provides a service to the terminal device;
• an authentication server that authenticates a user of the terminal device when the terminal device receives provision of the service from the service providing server;
• and an authentication intermediary server that selects the authentication server;
• wherein:
• the authentication intermediary server comprises a control part and a storage part that stores service providing server request information that specifies a service providing server ID and a requested condition requested in authentication by a service providing server corresponding to the service providing server ID;
• and
• the control part of the authentication intermediary server performs:
• processing, in which, when an information acquisition request specifying a service providing server ID is received from the service providing server, a requested condition corresponding to the service providing server ID specified by the information acquisition request is acquired from the service providing server request information, and the authentication server satisfying the acquired requested condition is selected;
• and
• processing, in which information specifying the selected authentication server is notified to the service providing server.