A Distributed Anonymous Reputation System for V2X Communication
Shahidatul Sadiah1,#, Toru Nakanishi2,#,*
1 Faculty of Electrical Engineering, Universiti Teknologi Malaysia, Johor Bahru, 81310, Malaysia
2 Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima, 739-8527, Japan
* Corresponding Author: Toru Nakanishi. Email: 
# These authors contributed equally to this work
(This article belongs to the Special Issue: Advances in IoT Security: Challenges, Solutions, and Future Applications)
Computers, Materials & Continua https://doi.org/10.32604/cmc.2025.073774
Received 25 September 2025; Accepted 19 December 2025; Published online 04 January 2026
Abstract
V2X communication enables vehicles to share real-time traffic and road-condition data, but binding messages to persistent identifiers enables location tracking. Furthermore, since forged reports from malicious vehicles can distort trust decisions and threaten road safety, privacy-preserving trust management is essential. Lu et al. previously presented BARS, an anonymous reputation mechanism founded on blockchain technology to establish a privacy-preserving trust architecture for V2X communication. In this system, reputation certificates without a vehicle identifier ensure anonymity, while two authorities jointly manage certificate issuance and reputation updates. However, the centralized certificate updates introduce scalability limitations, and the authorities can trace vehicle behavioral information, which threatens privacy guarantees. Several subsequent systems derived from BARS still rely on centralized certificate management and are subject to authority-side privacy leakage. As a result, a key challenge in this line of research remains unresolved: how to decentralize the certificate-update process while preserving privacy against the authorities in privacy-preserving V2X trust management. In this paper, we propose a distributed anonymous reputation system for V2X communication, based on an anonymous reputation system for crowdsensing. In our proposed system for V2X communication, the server is distributed to a certificate authority (CA) and roadside units (RSUs). Each vehicle shows the reputation level to the nearest RSU at the beginning of each time interval, and registers a short-time public key. In the interval, the messages from the vehicle are authenticated under the public key and are scored. At the end of the interval, the nearest RSU updates the certificate anonymously. Our solution decentralizes the certificate-update process by assigning each update to the nearest RSU. A zero-knowledge-proof-based show protocol removes the need for any central authority to handle vehicle certificates and thus prevents the authorities from tracing vehicle activities. Compared with BARS, where centralized authorities must update the reputation certificates of many vehicles and may incur communication and processing delays, our system performs each update locally at the nearest RSU once per interval. The required interaction consists only of a few kilobytes of communication and a zero-knowledge proof that is almost fully precomputed on the vehicle side, while the RSU-side processing is estimated to take about 40 ms based on timing measurements of the underlying cryptographic operations. This distributed update model avoids the centralized bottleneck of BARS and simultaneously removes the privacy risk arising from authority collusion.
Keywords
V2X communication; anonymous reputation system; proof of knowledge
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