2007 Reports

OpenTor: Anonymity as a Commodity Service

Androulaki, Elli; Raykova, Mariana Petrova; Stavrou, Angelos; Bellovin, Steven Michael

Despite the growth of the Internet and the increasing concern for privacy of online communications, current deployments of anonymization networks depends on a very small set of nodes that volunteer their bandwidth. We believe that the main reason is not disbelief in their ability to protect anonymity, but rather the practical limitations in bandwidth and latency that stem from limited participation. This limited participation, in turn, is due to a lack of incentives. We propose providing economic incentives, which historically have worked very well. In this technical report, we demonstrate a payment scheme that can be used to compensate nodes which provide anonymity in Tor, an existing onion routing, anonymizing network. We show that current anonymous payment schemes are not suitable and introduce a hybrid payment system based on a combination of the Peppercoin Micropayment system and a new type of "one use" electronic cash. Our system claims to maintain users' anonymity, although payment techniques mentioned previously --- when adopted individually --- provably fail.