Visor: Privacy-Preserving Reputation for Decentralized Marketplaces

Feedback mechanisms are crucial in e-commerce and collaborative systems, shaping trust, deterring dishonesty, and promoting good online behavior. Reputation, built through collective feedback, impacts vendor trustworthiness and support. However, centralized systems like eBay and Amazon pose privacy concerns as users must trust the central server to maintain accurate records and protect sensitive data. Decentralized solutions offer greater privacy and control over feedback, aiming to overcome the limitations of centralized ones. Yet, decentralized reputation systems face challenges such as susceptibility to Sybil attacks and more, which undermine user trust and system reliability. In this work, we propose Visor, a decentralized reputation system addressing these challenges by leveraging randomizable signatures and zero-knowledge proofs to construct a reputation mechanism that safeguards privacy and prevents misuse. The security properties of Visor are formally demonstrated; the system guarantees integrity and ensures that users remain anonymous during feedback, while also maintaining unlinkability among pseudonyms and reviews associated with the same user. Finally, the system provides users with a comprehensive view of all transactions, thereby enabling public verifiability without reliance on any trusted third party.