Patent ID: 8874903

Claim:
A network device, comprising: a communication unit configured to connect with a service providing server, an authentication server, and a terminal device via a network; an acquisition information storage configured to store a plurality of pieces of acquisition information each for acquiring a certificate corresponding to a specific one of a plurality of services provided by the service providing server, wherein the plurality of pieces of acquisition information includes: a first piece of acquisition information that establishes a first relationship between a first one of the services, a first one of a plurality of authentication servers including the authentication server, and a first user, among a plurality of users, who directly operates the network device; and a second piece of acquisition information that establishes a second relationship between a second one of the services, a second one of the plurality of authentication servers, and a second user, among the plurality of users, who accesses the network device via the terminal device; a certificate storage configured to store certificates, acquired from the authentication server, in association with the services, respectively; at least one processor; and memory storing computer-executable instructions that, when executed by the at least one processor, cause the network device to: accept, from a requestor among the plurality of users, a request for usage of one of the plurality of services provided by the service providing server; in response to acceptance of the request, determine whether a certificate necessary for utilizing the requested service is stored in the certificate storage by searching for the necessary certificate within the certificate storage based on a specific one of the pieces of acquisition information for acquiring the necessary certificate that is stored in the acquisition information storage in association with the requestor and the requested service; when determining that the necessary certificate is not stored in the certificate storage, read out the specific one of the pieces of acquisition information for acquiring the necessary certificate that is stored in association with the requestor and the requested service from the acquisition information storage, identify a specific one of the plurality of authentication servers associated with the requestor and the requested service, acquire the necessary certificate from the identified authentication server based on the specific piece of acquisition information read out, and store the acquired necessary certificate into the certificate storage; when determining that the necessary certificate is stored in the certificate storage, acquire the necessary certificate associated with the requested service from the certificate storage; send the necessary certificate to the service providing server; receive a permission to utilize the requested service from the service providing server; and utilize the requested service in response to receipt of the permission.