Generalized Secure and Dynamic Decentralized Reputation System With a Dishonest Majority

Abstract

Reputation management systems are essential for establishing trust among network users. They are tools for reinforcing cooperation and sanctioning malicious behavior. This importance becomes a requirement in decentralized environments such as mobile ad-hoc networks (MANETs), peer-to-peer systems (P2P), wireless sensor networks (WSNs), or decentralized social networks (DSNs) where there is no trusted third party to monitor and enforce good behavior among users. In this paper, we propose a dynamic decentralized reputation system that fits such network characteristics, namely decentralization, dynamism, and openness, without conceding on security. The novel system is a general-purpose system that uses blockchain to gather and supply global reputation information while remaining fully decentralized. Unlike previous works on decentralized reputation systems where reputation information is inconsistent and limited to users’ direct experience and recommendations from peers (neighbors), our system gathers feedback from all over the network and stores reputation information on a distributed ledger fully accessible to all users. In terms of security, the proposed method achieves privacy utilizing secure multiparty computation, a cryptographic primitive that preserves feedback privacy even with a dishonest majority reaching $n-2$ malicious parties while requiring only $O(n)$ messages. The employed techniques enable the system to achieve unique characteristics like consistency, conservation, and verifiability in addition to privacy. The security analysis we provide confirms these properties, and the performed simulation shows the protocol’s effectiveness.

Keywords

• Blockchain
• privacy
• reputation
• secure multiparty computation