BCRF-SC: Provably secure hybrid blockchain framework with firewalls for resilient VANETs

Intelligent Transportation Systems (ITS), driven by modern vehicular networks, demand robust security measures to maintain data integrity, user privacy, and system resilience against evolving malicious attacks. Existing security frameworks frequently rely on centralized trust mechanisms, resulting in single points of failure, elevated communication latency, and critical vulnerabilities to insider threats or secret key exfiltration from subverted cryptographic modules. This study proposes BCRF-SC, a hybrid blockchain framework integrated with cryptographic reverse firewalls (CRFs) designed to significantly enhance the security and reliability of VANET communications. The framework eliminates centralized trust by combining a Verifiable Secret Sharing-based Distributed Key Generation (VSS-DKG) protocol with a dual-layer blockchain architecture, thereby defending against identity forgery, single-point failures, and insider threats. By incorporating CRFs at both Roadside Units (RSUs) and Onboard Units (OBUs), BCRF-SC strengthens system resilience and provably prevents secret key leakage even when some nodes are partially compromised. We formally prove that BCRF-SC achieves confidentiality (IND-CCA2) and unforgeability (EUF-CMA) security, with its security guarantees established under the Computational Diffie–Hellman (CDH) and Discrete Logarithm (DL) assumptions. Performance evaluation demonstrates that BCRF-SC achieves low communication and computation overhead, supports efficient batch verification at RSUs, and scales to dense traffic scenarios, making it suitable for real-time ITS deployments.