Patent ID: 7165176

Claim:
A system comprising: a server that provides service to a client; the server further comprising: a public-key storage unit that stores a public key assigned to the service; a challenge generator that generates a challenge to be sent from the server to the client after the server receives a request for the service from the client; an access privilege verifier that verifies whether a prescribed relationship exists between the challenge and a response, the response being corresponding the challenge and received from the client; and the client that requests the service from the server, the client comprises: an unique operation executer that executes a first unique operation assigned to the client; an access privilege proving data storage unit that stores access privilege proving data, the access privilege proving data being created from a private key corresponding to a public key assigned to the requested service and result of a second unique operation; a response generator that generates the response to the challenge, the challenge being received from the server; wherein the response is calculated based on the first unique operation and the access privilege proving data, and wherein a valid response is not calculated unless the first unique operation coincides with the second unique operation.