Incentive Mechanisms for Anonymous Communication

Anonymous communication protocols, when implemented as peer-to-peer systems, are vulnerable to free-riders, peers that use the system while providing little or no service to others and whose presence limits the strength of anonymity as well as the efficiency of the system. In general, free-riding can be addressed by building incentive mechanisms into system protocols to promote cooperation among peers. However, the limited observability and privacy requirements of anonymous systems present challenging design constraints for incentive mechanisms.

In this talk I will present an incentive mechanism to promote high peer availability based on the exchange of currency in return for service, and describe how the scheme can be implemented without compromising privacy by embedding small anonymous digital payments in existing protocol messages. I will also describe an anonymity-preserving reputation mechanism to promote protocol compliance by identifying non-compliant peers who can then be isolated from the system. Used in conjunction, these two mechanisms provide an effective defense against free-riding. Peer availability can be significantly increased through the introduction of payments and peers consistently failing to comply with the protocol are successfully identified and isolated by the reputation mechanism.

The work presented was done jointly with Daniel Figueiredo and Don Towsley, both at UMass Amherst.

Jonathan Shapiro is an assistant professor in Computer Science and Engineering at Michigan State University. He received his B.A. from Columbia University, and M.S. and Ph.D. from the University of Massachusetts at Amherst. His primary research interest is the application of economics to problems in networks and distributed systems, including the use of pricing mechanisms for distributed resource allocation and the role of incentives in promoting cooperation among self-interested network users. Other research interests include congestion control, privacy and security, electronic commerce, and peer-to-peer systems.