A client device transmits service identification information to an authentication device at the time of a service request, prompts selection of one or more authentication entity devices which execute one or more authentication subprocesses from among all the authentication entity devices adaptive to profile information received from the authentication device, based on “function list information defining an execution environment of each of the authentication entity devices”, transmits a request for executing an authentication subprocess to such selected each authentication entity device, and transmits to the authentication device “authentication context information including an execution environment and an execution result of an authentication subprocess” received from such each authentication entity device.