Study on Agent Incentives for Resource Sharing on P2P Networks

There have recently been extensive studies on proportional response protocol, which is motivated by the successful BitTorrent system for file sharing over a P2P network. The proportional response protocol has been proved to be strategy-proof against weight cheating attacks and edge cheating attacks, in order to allocate a single type of resource on P2P networks. This strategy-proof property holds due to an elegant combinatorial structure: the bottleneck decomposition of the underlying network structure, and the utility function, defined as the total resources that one agent receives from its neighbors. However, Sybil attacks, under which an agent may form several fictitious players and split its resource among them, have been shown as a more difficult attack to defend against, and thus a strategic agent playing Sybil attacks may result in personal gain. Previous efforts have been made to show that an agent may generate a gain, but with limited gains by Sybil attacks on several special networks, including trees, cliques, and rings. This paper is the first to study the agent’s incentives by adopting a Sybil attack on general networks. The main contribution is to prove that any agent cannot obtain more than three times as much as the revenue when it plays honestly.