CAREER: Decentralizing Trust in Open Distributed Systems

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Distributed systems that allow any user to enroll his node as a participantmust resolve two main challenges to achieve reliability: selecting trustworthyparticipants, and detecting and containing the damage of deviant nodes. Thisresearch addresses these challenges by (a) presenting a new systemarchitecture, F2F, that incorporates decentralized trust relationships amongusers in determining trustworthy nodes and (b) devising new techniques todetect and contain faults of misbehaving nodes in the context of concreteapplications using this new architecture. This research demonstrates the usefulness of F2F through the design andimplementation of two case-study systems: cooperative backup and censorshipcircumvention. Friendstore provides inexpensive and reliable backup by storingeach user's data on a subset of trusted neighbors. Such an architecture allowsFriendstore to use less expensive technical means to detect and recover fromfaults but makes it harder to fully utilize storage resources. This project addresses this challenge using coding techniques that allow a node toefficiently provide data redundancy for multiple neighbors simultaneously. Thesecond case study system, Kaleidoscope, helps users inside censored domainsaccess blocked websites by relaying traffic via a network of proxies.Kaleidoscope uses a novel protocol to disseminate proxy identities over the F2Ftrust graph so that each node can only collect limited information aboutothers' identities. A few malicious nodes, then, cannot discover a significantfraction of proxies. This project will produce systems that, if successfully deployed, provideinexpensive online storage to home users and help circumvent censorship formillions of affected users.