On the security of polling protocols in peer-to-peer systems

The peer-to-peer (P2P) network model differs from the well established client-server model in that all members of the network are assigned an equal role. P2P networks are recently gaining increasing popularity. Providing security in distributed content sharing in P2P networks is an important challenge. This paper identifies security vulnerabilities in the protocols for sharing servants´ reputations in the Gnutella P2P system, proposed recently. It demonstrates attacks on the protocols that allow an attacker to alter the results of the voting procedure. The paper then presents a protocol that is resilient to the attacks described. In the proposed protocol, enhanced security against various attacks is achieved using smart design and a combination of various techniques such as the use of digital signatures for message integrity and random numbers for message freshness.