# Blockchain-Based Authentication in Internet of Vehicles: A Survey
## 4 Blockchain-Based Authentication Schemes in Vehicular Networks
### Consortium Blockchain-Based Authentication Protocols
However, the TA is responsible for other system phases namely, system initialization, smart contract deployment, vehicle registration, and vehicle revocation phases. The scheme deploys a technique based on fuzzy extractor for biometrics extraction and an Attribute-Based Encryption (ABE) scheme to protect the privacy of users by encrypting their blinding identities to ensure that no other entity can decrypt them except for the blockchain managers. During the system initialization phase, the TA initiates the system parameters including the ECC, the ABE, and the blockchain parameters. A smart contract is then deployed by the TA into the blockchain to automate the authentication process. Each vehicle then needs to be registered with the TA to obtain its secret authentication parameters during the registration phase. First, the owner of a vehicle must choose a physical identity, a password along with his/her biometrics which will be sent to the TA. The TA then calculates a corresponding blinding identity (AID) and a Vehicle Public Key (VPK) from the received parameters and uploads them as a unique tuple {AID, VPK} to the Vehicle Public Key Table (VPKT) in the smart contract. The AID is also sent to the vehicle's OBU which is assumed to be tamper-proof. When a vehicle wishes to send data to nearby vehicles or RSUs, the vehicle's owner provides the login information (i.e., password and biometrics) which are verified by the OBU. If correct, the OBU encrypts the vehicle's AID using the ABE and sends it along with the message and a timestamp to the receiver (i.e., a vehicle or RSU), otherwise, the OBU rejects the message. The receiving entity then validates the freshness of the message through the timestamp. If valid, it initiates a transaction to the blockchain managers requesting for the associated vehicle public key. The blockchain managers then lookup the VPKT using the AID to obtain the corresponding VPK which is then transmitted to the transaction issuer to be verified. Upon successful validation, the authentication is completed, and the message is accepted. BPAS also supports conditional traceability and vehicle's revocation in case of detecting any malicious behavior by simply allowing the TA to delete the corresponding tuple in the VPKT. The proposed scheme is evaluated in terms of time cost and security features and is found to be resistant to replay attacks, impersonation attacks, DDoS, and password guessing attacks. The authors in [133] proposed an Efficient Authentication Scheme over Blockchain for Fog computing-enabled IoV (EASBF). The authors consider three types of communication in their fog-enabled model, i.e., V2V, V2I, and V2R. Each fog area can provide different services to users and vehicles within its coverage range, and it includes one or more RSUs, one or more CAs, a single Blockchain Manager (BM), and a single Authentication Manager (AM). The CAs are trusted entities responsible for updating and managing the certificates issued for vehicles in their fog areas. The BMs are deployed to manage the blockchain and authenticate the OBUs whereas the AMs write the results of authentication into the blockchain (which together form the consortium blockchain). The PBFT is used for consensus. The proposed scheme contains five phases: initialization, registration, mutual authentication and key exchange, consensus, and certificate update. A central secured entity, named TA, is responsible for initializing the system and the public parameters used for the cryptographic functions, as well as registering the OBUs and RSUs during the first two phases of EASBF. Then, mutual authentication and key exchange takes place between OBUs and BMs, and a session key is shared among them for subsequent interactions. Upon successful authentication and key exchange, the BM shares the results of authentication with all AMs, which store them into a new block and add it to the large public register under the PBFT consensus.