# Privacy-Preserving Solutions in Blockchain-Enabled Internet of Vehicles
## 6 Privacy-Preserving Blockchain-Based Solutions
### General Services  
Here are two general solutions that promise to provide privacy protection in blockchain-enabled IoV. [PERSON] et al. [3] proposed a general decentralised architecture for VANET aiming to protect identity and location privacy. The system is starting with the initialisation of the blockchain network, where the edge nodes, which are the nodes that run the smart contracts and participate in the consensus, are equal and enjoy the same rights and obligations. Then, the registration process occurs where a Certification Authority server, through smart contracts, validates a vehicle into the blockchain network. If the validation fails, the details are recorded in a block and broadcasted to the network, so that all participants are warned. To protect the identity and the location of vehicles during message broadcasting, the proposed system adopts the k-anonymity unity. When a vehicle is ready to transmit a message, with the help of an RSU it forms a group with the nearby vehicles, then selects other \(k-1\) sub-identities including his own and all the messages are uploaded together, so the server of the core network cannot identify the location and the identity of the vehicle. Every message is considered as a transaction and recorded in the blockchain network. After the transmission of the message, the agent broadcasts the block to all nodes and using practical byzantine fault tolerance as consensus algorithm, the transactions are validated. The validated blocks are stored on every node. To be protected against any thread, this system uses undirected graph generation algorithm for privacy protection of the vehicles, a way of dynamic threshold encryption to protect the vehicular identity and the k-anonymity unity to protect location privacy. The security evaluation performed in simulation environment using OPNET and Ethereum. As a result of the evaluation, the proposed system seems to be faster than the commodity blockchain solutions and the location privacy greatly improved. [PERSON] et al. [60] proposed an intelligent transportation system, called Ba-ITS, based on permissioned Blockchain technology that aims to provide different vehicular services. The proposed structure consists of three layers called ITS network infrastructure layer, cloud computing and service provisioning layer and blockchain overlay layer. Aiming to concentrate only in data of a certain area, three layers of private hierarchical blockchains are used, called vehicle-chain (V-chain), RSU-chain (R-chain) and gateway-chain. Vehicle-chain consists of vehicles and RSUs in order to upload or obtain data and services. RSU-chain consists of RSUs and the gateway in which they are connected and its purpose is to synchronise data from different vehicle-chains. The gateway-chain aims to ensure data exchange among different gateways and has the highest priority in the network as it maintains all data. The main components of gateway-chain are a gateway, server nodes and a router. Some nodes participate in several chains in order to synchronise data between them. When exchanging data, vehicles collect data using sensors and upload them to the system in order to inform other vehicles for road conditions, and as a reward they gain some points which they can use in the future to request data or services. In services such as route planning, in contrast with traditional navigation services where location information of vehicles are collected and stored, in this proposed model, root is performed by a smart contract. Therefore, private information of users are protected. In addition, data exchanges involve only blockchain address of vehicles, thus no personal data is provided. Moreover, smart contract and transactions support data exchanging and other services, ensuring that privacy is better protected. Furthermore, the privacy is implemented by using private chains with access control and by encrypting the data stored in V-chain. The authors implemented their model using Ethereum Blockchain.