# Blockchain-Based Authentication in Internet of Vehicles: A Survey
## 4 Blockchain-Based Authentication Schemes in Vehicular Networks
### Private Blockchain-Based Authentication Protocols  
A private blockchain is a limited access blockchain in which only a particular group of trusted entities (which is decided by a network administrator) is granted access permissions to the blockchain transactions for performing specific tasks. The nature of private blockchains enables establishing a high level of trust during authentication since only a small group of trusted nodes are allowed to access the vehicles' authentication parameters stored in the blockchain. Additionally, being controlled by a single organization allows easier, more efficient management and supervision over the authentication data kept at the ledger. Consequently, private blockchains are implemented by many researchers to serve authentication purpose in IoV platforms. The authors in [111] incorporated a private blockchain technology with intelligent contract to address the issue of new nodes joining the IoV network. The intelligent contract is designed initially for the verified cloud servers, roadside units and vehicle manufacturers which form a contract node group that use Rayleigh consensus mechanism to authorize or reject the new joining requests. When a new node sends a registration application to join the contract group, each node in the contract node group evaluates the received application and grants its digital signature if it agrees to trust the node, otherwise no digital signature is granted. Then, if 51% of the contract nodes grant their signatures, the node is accepted to the contract node group and a new block is added to the chain. Otherwise, the node's information is added to the list of suspicious nodes and broadcasted to the rest of the \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Attack Targets** & **Description** & \multicolumn{2}{c}{**Examples**} & **Attack Type** \\ \hline \multirow{3}{*}{Confidentiality} & Attacks that compromise the privacy of data through & - & Man-in-the-middle attack & Passive/Active \\  & receiving unauthorized copies of the messages being & - & Eavesdropping attack & Passive \\  & transmitted between the legitimate sending and & - & Message holding attack & Active \\  & receiving entities by an illegal third party. & - & Eavesdropping attack & Passive \\ \hline \multirow{3}{*}{Routing} & Attacks that manipulate the original route of a packet & - & Eavesdropping attack & Active \\  & by injecting some malicious recipients in the middle to & - & Denial of service attack & Active \\  & eavesdrop or even sometimes alter the message before & - & Masquerading attack & Active \\  & further forwarding it towards its targeted destination. & - & Route modification attack & Active \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._ \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Attack** & **Targeted OSI Layer** & **Possible Solutions** & **References** \\ \hline \multirow{3}{*}{Sybil attack} & \multirow{3}{*}{Network layer} & Group signatures, session key & \multirow{3}{*}{[100; 101; 102; 103]} \\  & & certificates, event based & & \\  & & reputation system, footprint & \\ \hline \multirow{2}{*}{GPS deception attack} & \multirow{2}{*}{Physical layer} & Dead reckoning, signature-based & \multirow{2}{*}{[104; 105]} \\  & & mechanisms & \\ \hline \multirow{2}{*}{Masquerading/Impersonation attack} & Multi-layer (Physical, Data link, Network, Transport, and Application layers) & Digital certificates, identity-based cryptography & \\ \hline \multirow{2}{*}{Wormhole attack} & Network layer & Geographical leashes & [108; 109] \\ \hline \multirow{2}{*}{Replay attack} & Network layer & Timestamps & [110] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Possible attacks on authentication, their targeted OSI layers, and remedies. network to block its future joining attempts. This results in suppressing the joining of malicious nodes from the root.