Building Incentives into Tor

Abstract

Distributed anonymous communication networks like Tor depend on volunteers to donate their resources. However, the efforts of Tor volunteers have not grown as fast as the demands on the Tor network. We explore techniques to incentivize Tor users to relay Tor traffic too; if users contribute resources to the Tor overlay, they should receive faster service in return. In our design, the central Tor directory authorities measure performance and publish a list of Tor relays that should be given higher priority when establishing circuits. Our system provides an acceptable anonymity tradeoff and improves performance while incentivizing Tor users, across the whole network, to contribute the resources necessary for Tor to better support its users’ needs. Simulations of our proposed design show that conforming users receive significant improvements in performance, in some cases experiencing twice the network throughput of selfish users who do not relay traffic for the Tor network.