Trustworthy and scalable anonymous communication

The architectures of deployed anonymity systems such as that of the Tor network suffer from the problems of (a) limited scalability, (b) reliance on a few central points of trust, and (c) trust issues due to Sybil attack. In this thesis, we investigate the design of novel approaches to anonymous communication that are scalable, decentralized, and Sybil-resilient. First, we begin by investigating security vulnerabilites in existing P2P anonymity systems, and find fundamental limitations in their designs. Second, we propose novel protocols for P2P anonymous communication that can successfully overcome these limitations. Third, we describe a protocol for detecting malicious Sybil identities using information about social network trust relationships. Fourth, we present protection mechanisms for DHTs that also leverage social network trust relationships to defend against the Sybil attack while preserving the privacy of social contacts and providing a basis for pseudonymous communication. Finally, we describe a protocol for trustworthy and scalable anonymous communication that can directly leverage users’ trusted social contacts. We evaluate the effectiveness of our protocols using theoretical analysis, simulations, implementations and a Facebook application