FS-CLAS: A Forward-Secure Pairing-Free Certificateless Aggregate Signature Scheme for VANET Authentication

We introduce a forward-secure, pairing-free, and certificateless aggregate signature scheme called FSCLAS to support efficient, lightweight, and scalable authentication in VANETs. Overview: To accomplish forward secrecy, FS-CLAS uses a hash-chain-based design for key evolution that does not require bilinear pairings or secure hardware modules. It is secure against side-channel attacks due to the usage ofephemeral keys and constant-time scalar multiplication, and it features batch verification capability, conditional traceability, and decentralized revocation using Bloom filters. A modular app and management architecture make our implementation compatible with real-world Intelligent Transportation System (ITS)deployments. We demonstrate through experimental evaluation that FS-CLAS achieves up to 50% reduction in verification latency and 42% saving of communication overhead as compared to more recent work, where the average signing and verifying times are less than 3.2ms and 6.7ms, respectively, on ARM-based OBUs. Results from simulations with SUMO and NS-3 show that they work well under variable traffic density levels and high vehicle mobility. FS-CLAS complies with IEEE 1609.2 and ETSI ITS-G5 standards, providing an option for deployment with existing and future V2X networks.