Cryptology ePrint Archive: Report 2016/464

Beaver: A Decentralized Anonymous Marketplace with Secure Reputation

Kyle Soska and Albert Kwon and Nicolas Christin and Srinivas Devadas

Abstract: Amid growing concerns of government surveillance and corporate data sharing, web users increasingly demand tools for preserving their privacy without placing trust in a third party. Unfortunately, existing centralized reputation systems need to be trusted for either privacy, correctness, or both. Existing decentralized approaches, on the other hand, are either vulnerable to Sybil attacks, present inconsistent views of the network, or leak critical information about the actions of their users. In this paper, we present Beaver, a decentralized anonymous marketplace that is resistant against Sybil attacks on vendor reputation, while preserving user anonymity. Beaver allows its participants to enjoy open enrollment, and provides every user with the same global view of the reputation of other users through public ledger based consensus. Various cryptographic primitives allow Beaver to offer high levels of usability and practicality, along with strong anonymity guarantees. Operations such as creating a listing, purchasing an item, and leaving feedback take just milliseconds to compute and require generating just a few kilobytes of state while often constructing convenient anonymity sets of hundreds of transactions.

Category / Keywords: applications / reputation systems; anonymity; e-commerce; consensus

Date: received 12 May 2016, last revised 20 Aug 2016

Contact author: ksoska at cmu edu

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Version: 20160820:232252 (All versions of this report)

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