@MISC{n.n._optimalsybil-resilient, author = {n.n.}, title = {Optimal Sybil-resilient Node Admission Control}, year = {} }

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Abstract

Most existing large-scale networked systems on the Internet such as peer-to-peer systems are vulnerable to Sybil attacks where a single adversary can join the system using many fake identities. One promising defense is to perform social-network based node admission control to bound the number of Sybil identities admitted; the assumption here is that an adversary has very few social links with honest users (attack edges). SybilLimit and SumUp, two recent works, can restrict the number of Sybil identities admitted per attack edge to O(log n) with high probability; while SybilLimit is a decentralized protocol, SumUp is a centralized approach where the graph is known. In this paper, we propose an optimal decentralized admission control protocol that admits O(1) Sybil identities (with high probability) in an expander-like social network in the face of O(1) attack edges. In the face of o ( n log n) attack edges, our protocol admits O(log n) Sybil identities per attack edge with high probability. In other words, when the number of attack edges are small, we can design an optimal admission control protocol. This improves over existing results by a factor log n. We also demonstrate the effectiveness of our protocol experimentally on real-world social networks and synthetic topologies.