Cryptology ePrint Archive: Report 2020/761

Decentralized reputation

Tassos Dimitriou

Abstract: Reputation systems constitute one of the few workable mechanisms for distributed applications in which users can be made accountable for their actions. By collecting user experiences in reputation profiles, participants are encouraged to interact more with well-behaving peers hence better online behavior is motivated.

In this work, we develop a privacy-preserving reputation scheme for collaborative systems such as P2P networks in which peers can represent themselves with different pseudonyms when interacting with others. All these pseudonyms, however, are bound to the same reputation token. This allows honest peers maintain their good record even when switching to a new pseudonym, while preventing malicious peers from making a fresh start. Apart from an initial offline setup phase which is only needed to ensure reputation soundness but not privacy, our system is truly decentralized. Using an append-only distributed ledger such as Bitcoin’s blockchain, we show how participants can make anonymous yet verifiable assertions about their own reputation. Thus the system maintains soundness, peer-pseudonym unlinkability as well as unlinkability among pseudonyms of the same peer. We formally prove these properties, we discuss ways to eliminate the setup phase and we evaluate the efficiency of the various operations.

Category / Keywords: applications / Reputation, Decentralization, Privacy, Peer-to-peer networks, Collaborative systems, Blockchain, zkSNARKs

Date: received 21 Jun 2020

Contact author: tassos dimitriou at ieee org

Available format(s): PDF | BibTeX Citation

Version: 20200621:174557 (All versions of this report)

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