# Blockchain-Based Authentication in Internet of Vehicles: A Survey
## 4 Blockchain-Based Authentication Schemes in Vehicular Networks
### Private Blockchain-Based Authentication Protocols
The proposed message authentication scheme includes six phases: initiation, registration, message signing, message verification, block generation, and block confirmation. In the initiation phase, the RTA generates its public-private key pair, the genesis block of the blockchain and the list of LTAs. During the registration phase, a vehicle's owner sends the vehicle's information and its biometric information to the RTA which in turn generates a pair of asymmetric keys and transfers it along with the system key to the vehicle's local memory. The registration of LTAs also takes place in this phase by the RTA in the same approach as the vehicles' registration. When a vehicle needs to broadcast a message into the network, it computes the message's hash value h(m) and concatenates it with the hash values of the previous blocks in the blockchain and encrypts them together with its private key. This arrangement is then attached as a header to the actual message content along with a timestamp and encrypted with the system key before being broadcasted to other vehicles. This process of message signing guarantees the legitimacy of the sending vehicle and thus the authenticity of the broadcasted information since the unauthorized vehicles cannot have the system key used for message signing as it is distributed only to the registered vehicles during the registration phase. As the V2V messages are broadcasted among the vehicles, the corresponding LTA keeps collecting those messages until it forms a block after a certain number of messages. The block is then verified through the PBFT consensus by the vehicles and their LTA. Oncethe block is verified, the LTA transfers it to the other LTAs for block confirmation process. If confirmed by all LTAs, they send the confirmed block to the RTA which then concatenates the block officially into the blockchain. The simulation results reveal that the proposed scheme can prevent impersonation attacks and single point of failure issue while providing a highly efficient blockchain-based authentication in terms of the total consensus delay and throughput. The above-mentioned private blockchain-based authentication schemes can be found in Table 4 for easy reference. \begin{table}
\begin{tabular}{p{12.8 pt} p{12.8 pt} p{12.8 pt} p{12.8 pt} p{12.8 pt} p{12.8 pt} p{12.8 pt} p{12.8 pt} p{12.8 pt} p{12.8 pt} p{12.8 pt} p{12.8 pt}} \hline \hline
**Ref. ** & **Technique** & **Attack Counteracted** & **Network Model and Enties (Other than Blockchain)** & **Evaluation** & **Metrics** & **Features and Limitations** & **Privacy Preservation of Vehicle’s Identity? ** \\ \hline \hline \multirow{8}{*}{[111]} & \multirow{8}{*}{- Rayleigh consensus mechanism - Intelligent contract - P87I based on password accumulator} & & - V2I - vehicles - TRI based on & & & - Provides an efficient key distribution & \\  & & & - V2I - vehicles - RRUs - Trusted contract & & & & & & & \\  & & & - VRUs (cloud (OMC) - PKI based on password accumulator & & & & & & & \\  & & & & & & & & & \\  & & & & & &