  The Internet of Vehicles (IoV) can significantly improve transportation
efficiency and ensure traffic safety. Authentication is regarded as the
fundamental defense line against attacks in IoV. However, the state-of-the-art
approaches suffer from several drawbacks, including bottlenecks of the single
cloud server model, high computational overhead of operations, excessive trust
in cloud servers and roadside units (RSUs), and leakage of vehicle trajectory
privacy. In this paper, BEPHAP, a Blockchain-based Efficient Privacy-preserving
Handover Authentication Protocol with key agreement for internet of vehicles,
is introduced to address these problems. BEPHAP achieves anonymous cross-domain
mutual handover authentication with key agreement based on the tamper-proof
blockchain, symmetric cryptography, and the chameleon hash function under a
security model that cloud servers and RSUs may launch attacks. BEPHAP is
particularly well suited for IoV since it allows vehicles only need to perform
lightweight cryptographic operations during the authentication phase. BEPHAP
also achieves data confidentiality, unlinkability, traceability,
non-repudiation, non-frameability, and key escrow freeness. Formal verification
based on ProVerif and formal security proofs based on the BAN logic indicates
that BEPHAP is resistant to various typical attacks, such as man-in-the-middle
attacks, impersonation attacks, and replay attacks. Performance analysis
demonstrates that BEPHAP surpasses existing works in both computation and
communication efficiencies. And the message loss rate remains 0 at 5000
requests per second, which meets the requirement of IoV.
