# Privacy-Preserving Solutions in Blockchain-Enabled Internet of Vehicles
## 6 Privacy-Preserving Blockchain-Based Solutions
### Traffic Conditions
The designed architecture is composed by three layers. The first layer is the permissioned blockchain architecture where a set of anonymisers take the place of the miners and maintain a blockchain consortium. On the second layer, between blockchain and Vehicles, are deployed the RSUs, to serve as intermediate nodes, to help collect data and for trusting evaluation. Finally, in the third layer, we found the users (vehicles) where they can broadcast or receive location relative information, within a small area. To achieve the data immutability and trust, only anonymiser can propose a block. The anonymiser sends his proposal to anonymiser president, who is being elected by timestamp voting and who is in charge of validating a block. If the president validated a block, then he added it to the chain, based on the timestamp, and broadcasted it to the network. The difference between the traditional blocks is that the TCAC block header includes more information, such as the ID of the anonymiser that proposed the block, the signature of Merkle tree root added by anonymiser, the ID of a vehicle that sends request based on its current location, the ID of cooperative vehicles set, the number of the location information, marked as true, false or rejected, of the particular vehicle and the block ID with the most recent change in location information status. Moreover, the authors to avoid chain load have created a redundant block deletion strategy, where blocks, based on the number of the recorded data, are considered to be deleted. In TCAC, when a vehicle inserts the anonymiser's area, it gets a pseudonym and when a vehicle broadcasts location related data, the anonymiser choose \(k-1\) more nearby vehicles, based on the vehicle's reputation, to perform the location cloak and preserve the privacy of the broadcaster. If the anonymiser finds that the broadcast is made outside of his area, it flags the transmission as false and lowers the vehicle's reputation; in contrast, when the transmission is legit it increases the reputation of the vehicle. Additionally, if a region is populated by one anonymiser, it can be easy for an attacker to find the vehicle's location; for that reason more than two anonymisers must overlap each other's region in order to form a region-cross cloaking area. Finally, the authors have contacted a python simulation between their scheme and a traditional cloaking area construction system and their proposal performed better in detection of dishonest vehicles and false alarms. [PERSON] and [PERSON] [48] proposed a location and identity privacy scheme for VANET called BELP. The proposed system consists of a Registered Authority (RA), the users (vehicles) and RSUs. When a vehicle enters an RSU territory, it sends a join request to the nearest RA and RSU. RA is responsible to determine if the vehicle is eligible to join the network, using smart contract pre-made rules. If the vehicle is qualified by the rules, RA index the vehicle with a pseudonym. All the data will be registered into the federated blockchain by all RAs. Vehicles that participate in the network can exchange information using their pseudonyms. To preserve the location privacy and to avoid traceability, at any time a vehicle can change its pseudonym using random encryption period. When a pseudonym change occurs, it is mandatory that the vehicles are not less that two and the vehicle should change its speed and direction. Simulation in OPNET indicates that the proposed system preserves the identity and location privacy efficiently.