A Secure Group Agreement (SGA) Protocol for Peer-to-Peer Applications

The lack of a trusted central authority poses a unique security challenge to peer-to-peer networks. It must be assumed that some fraction of all peers in a network are corrupt and may collude to try to derive an advantage. Nonetheless, in some circumstances it is necessary to select a subset of the peer-to-peer network in such a way that all members of the selected group can be confident that most group members are honest. We propose a secure protocol for the selection of a subset of peers from the network without a trusted authority. Our protocol ensures, with any desired probability, that the percentage of corrupt members in the subset is no greater than a selected limit (up to the total percentage of corrupt peers). We then discuss the use of this protocol in the context of a peer-to-peer game.