Patent ID: 7520431

Claim:
A communication system comprising: an IC module in which one or more applications are loaded; a controller in which counter-applications compatible with the applications are loaded; and a reader/writer that reads or writes information from or in the IC module in response to an instruction issued from the controller, wherein: the reader/writer includes: a memory in which one or more pieces of IC access authentication information that are associated with the applications loaded in the IC module and that are used for mutual authentications between the reader/writer and the associated applications respectively are stored and in which pieces of group authentication information are stored in association with groups into which the pieces of IC access authentication information are sorted according to the applications; and when the reader/writer is requested to write or read information in or from the IC module by any counter-application in the controller, the reader/writer and the counter-application mutually authenticate using group authentication information; if the mutual authentication succeeds, the reader/writer and an application in the IC module mutually authenticate using IC access authentication information belonging to a group identified with the group authentication information used for the successful mutual authentication; and if the mutual authentication succeeds, the reader/writer reads or writes information from or in the IC module in response to an instruction issued from the counter-application.