Blockchain Empowered Trustworthy Access Scheme for 6G Zero-trust Vehicular Networks

6G networks will bring the new paradigm of ubiquitous intelligence and on-demand services in all scenarios, in which trustworthy and reliable network services become key technical indicators. Facing the communication requirements in the 6G zero-trust environment, the blockchain is used as a "trust bridge", and the trusted and reliable access management scheme of the 6G in-vehicle network is studied in this paper. Firstly, a zero-knowledge authentication algorithm based on quadratic residual is used to complete the mutual authentication and authorization between the base station and the vehicle without exposing the privacy of the vehicle. Then, in order to improve the verification efficiency and save the energy consumption of the base station, a road redundant computing power incentive model based on the contract theory is established, and part of the verification tasks of the base station are allocated to edge servers or parked vehicles and given corresponding rewards. Finally, a 6G zero-trust network architecture of vehicle based on two-tiered blockchain is established. The primary chain maintained by the base stations and the secondary chain maintained by the edge computing nodes are used to record the important parameters of the identity verification of the vehicular networks, so as to meet the requirement of trustworthy access in the zero- trust environment. Compared to the existing baseline approaches, the proposed scheme improves significantly the vehicle verification efficiency and reduces the energy consumption of the base station without revealing the privacy of the vehicles.