In this paper we present Laribus, a peer-to-peer network designed to detect local man-in-the-middle attacks against secure socket layer/transport layer security (SSL/TLS). With Laribus, clients can validate the authenticity of a certificate presented to them by retrieving it from different vantage points on the network. Unlike previous solutions, clients do not have to trust a central notary service nor do they have to rely on the cooperation of website owners. The Laribus network is based on a social network graph, which allows users to form notary groups that improve both privacy and availability. It integrates several well-known techniques, such as secret sharing, ring signatures, layered encryption, range queries, and a distributed hash table (DHT), to achieve privacy-aware queries, scalability, and decentralization. We present the design and core components of Laribus, discuss its security properties, and also provide results from a simulation-based feasibility study.

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