# Blockchain-Based Authentication in Internet of Vehicles: A Survey
## 4 Blockchain-Based Authentication Schemes in Vehicular Networks
### Consortium Blockchain-Based Authentication Protocols
The system model consists of multiple regions; each region is managed by a Service Manager (SM) which is responsible for authenticating all OBUs and managing all Vehicular Fog Datacenters (VFDs) represented by the RSUs in its region. A Witness Peer (WP) exists in each region to write the authentication logs to the ledger maintained by the corresponding SM. The ledger is only accessible by the members of the consortium blockchain, such as the SMs, the WPs and the audit department which is assumed to be a fully trusted authority responsible for registering all the network entities underneath. The RSUs within a region serve as access points to the vehicles in the IoV paradigm and also as fog computing units for providing real-time services to authorized OBUs. The proposed BLA protocol includes five phases: initialization, registration, authentication, consensus, and service-delivery phases. The initialization phase takes place only once via the initial setup of system parameters by the audit department. Then, the registration of SMs and OBUs is conducted by the audit department during the registration phase in which each registered entity is allocated a pair of private and public keys using Elliptic Curve Cryptography (ECC) and Diffie-Hellman (DH) cryptography mechanisms. During the authentication phase, each SM authenticates the OBUs within its region, and the authentication results are then passed to the subsequent phase where they are written to the ledger by the consensus makers, i.e., WPs, through PBFT consensus protocol. The way they addressed the cross-datacenter authentication is by allowing a flexible option to vehicles to choose whether to be reauthenticated or not upon entering a new VFD during the service-delivery phase. The noninteractivity property that BLA has, in which a vehicle sends only one message to its SM for authentication or service requesting without the need for exchanging any acknowledgement messages between them, makes it lightweight in both communication and computation cost. In addition, the utilization of pseudonym preserves the privacy of vehicles and ensures anonymity. Security analysis proves that the proposed BLA protocol ensures most of the security aspects in IoV network, such as confidentiality, integrity, traceability, and non-repudiation. Moreover, extensive simulations are performed to measure the performance in terms of response time. The results obtained show that low time overhead is achieved which reflects the suitability of BLA algorithm for real-time VFS. The authors in [131] improved the reliability of the authentication scheme proposed in [130] through the adoption of mutual authentication and key exchange mechanism. During the authentication phase, instead of just allowing one-way authentication in which only the SMs can check the authenticity of vehicles [130], a two-way authentication is enabled in [131] where a SM first authenticates the identity of a vehicle using the ECC then the vehicle authenticates the communicating SM in the same way. Upon successful mutual authentication, a session key is established and exchanged between the two parties for securing their future communication; which is a prerequisite for secure authentication protocol, unlike the work done in [130]. Moreover, the scheme guarantees the forward secrecy. The timestamps used for generating the authentication parameters prevent replay attacks. An extensive performance evaluation and comparison is conducted which reveals that the proposed solution outperforms the work in [130] in terms of communication and computational overheads. The authors in [132] proposed a Blockchain-based Privacy preserving Authentication System (BPAS) for VANETs which supports password and biometric login-based authentication. BPAS relieves the overhead of having an online registration center during the authentication phase by providing a TA-independent authentication scheme in which vehicle's authentication is handled by RSUs or other vehicles in the network.