Malicious User Limit: A Decentralized Approach against Sybil Attacks

Abstract

Peer-to-peer and other decentralized, distributed systems are known to be particularly vulnerable to Sybil attacks. In a Sybil attack, a malicious user obtains multiple fake identities and pretends to be multiple, distinct nodes in the system. By controlling a large fraction of the nodes in the network, this paper presents Sybil Limit, a novel protocol for limiting the corruptive influences of Sybil attacks. Sybil limit a new protocol for defending against Sybil attacks without relying on a trusted central authority. Sybil limit leverages a key insight regarding social networks. The edges connecting the honest region and the Sybil region are called attack edges. Sybil limit, a novel protocol for limiting the corruptive influences of Sybil attacks. This protocol is based on the social network among user identities, where an edge between two identities indicates a human-established trust relationship. It ensures that the number of attack edges is independent of the number of Sybil identities, and is limited by the number of trust relation pairs between malicious users and honest users. Sybil limit leverages the existing human-established trust relationships among users to bind both the number and size of Sybil groups.