Whanau: A Sybil-Proof Distributed Hash Table

Abstract

Whānau is a novel routing protocol for distributed hash tables (DHTs) that is efficient and strongly resistant to the Sybil attack. Whānau uses the social connections between users to build routing tables that enable Sybil-resistant lookups. The number of Sybils in the social network does not affect the protocol’s performance, but links between honest users and Sybils do.When there are n well-connected honest nodes, Whānau can tolerate up to O(n/ log n) such “attack edges”. This means that an adversary must convince a large fraction of the honest users to make a social connection with the adversary’s Sybils before any lookups will fail. Whānau uses ideas from structured DHTs to build routing tables that contain O([sqrt]n log n) entries per node. It introduces the idea of layered identifiers to counter clustering attacks, a class of Sybil attacks challenging for previous DHTs to handle. Using the constructed tables, lookups provably take constant time. Simulation results, using social network graphs from LiveJournal, Flickr, YouTube, and DBLP, confirm the analytic results. Experimental results on PlanetLab confirm that the protocol can handle modest churn.