ReDS: reputation for directory services in P2P systems

P2P systems rely on directory services for locating peers with the desired content and services. Directory services are themselves decentralized, such as with distributed hash tables (DHTs) that allow for efficient locating of objects without a centralized directory. As a system distributed over a diverse set of untrusted nodes, however, directory services must be resilient to adversarial behavior by such malicious insiders. While redundancy-based DHTs such as Salsa and Halo mitigate the effects of adversarial behavior, they incur substantial overhead due to redundant lookups. We propose Reputation for Directory Services (ReDS), a framework for using reputation management to enhance the security and reduce the costs of redundancy-based DHTs in the face of insider attacks. We present ReDS designs for both Salsa and Halo, and we show that peers can significantly boost the success rates of directory lookups by considering past performance. For example, our simulations show that Salsa-ReDS can reduce lookup failure rates by up to 94%. We find that applying ReDS effectively cuts the redundancy required by both Salsa and Halo in half to get comparable results.