Patent ID: 7117368

Claim:
A system comprising: a participant subsystem that is authorized to anonymously participate in a plurality of sessions using secret information provided by a manager subsystem, all of said secret information being transmitted to the participant subsystem prior to participation in a first of said plurality of sessions, said secret information enabling participation in each of the plurality of sessions; and a reception subsystem; wherein the participant subsystem comprises: an anonymous signing section for authorizing particular individual data using the secret information depending on session-related information to produce anonymous participation data with an anonymous signature; wherein the reception subsystem comprises: an anonymous signature determining section for determining whether received data is said anonymous participation data with said anonymous signature; and a sender match determining section for determining whether anonymous signatures of two different pieces of anonymous participation data representing two different contents of individual data that are received in a same session of said plurality of sessions are signed by an identical participant subsystem; and wherein participation by said participant subsystem in a plurality of different sessions is concealed from said reception subsystem.