# Privacy-Preserving Solutions in Blockchain-Enabled Internet of Vehicles
## 6 Privacy-Preserving Blockchain-Based Solutions
### Authentication
EVSP uses encrypted information in order to schedule charging of an EV and a charging-token is returned to the EV which sends a cryptocurrency deposit as a warranty; this is the same for every EV to prevent fake charging schedules. During charging procedure, the charging station receives the EV's charging-token to confirm that it is the scheduled one. Moreover, they improved their approach by using a Pederson Commitment rather than the token mechanism, in order to improve the efficiency and reduce the cost of provided services. The basic changes in this approach are that the EVs do not only receive from EVSPs the proving key and function that they have to solve but also the Pederson Commitment parameters. The function is also more difficult than the previous case in order to be more cryptographically secure. If the EV can open Pederson Commitment, it can schedule charging. With the given elements, EV creates its own commitment. Furthermore, the EV is aware of its preferred scheduled charging slot, as it is contained it the commitment, so it encrypts a message that EVSP can later decrypt to book the charging station. The EV verification during charging procedure is done through a comparison of EV's and EVSP's commitment. This comparison is accomplished by EVSP while the equality of those two commitments proves that the EV is the scheduled one. Like their first approach, EV use pseudonym addresses and a deposit in the form of cryptocurrency to pay for charging. Furthermore, in both approaches, a single smart contract is responsible for all EVs to improve the performance and efficiency of those models. Through security and privacy analysis, the authors have proved that their two approaches ensure that personal information of vehicles, like their ID or location, can be securely protected by usingzkSNARKs, because EVSP can authenticate EVs without knowing any other information. Additionally, charging stations also cannot access any personal data, as they are only aware of the anonymous identities of EVs, and malicious users cannot match the Ids to their real users or obtain another information from the blockchain. Regarding the payment method, as it can by accomplished through cryptocurrency and blockchain, anonymous payment is permitted without using a credit card, thus protecting the privacy of users. Both proposed models were evaluated by using Zokrates, a toolbox for zkSNARKs on Ethereum, and results have shown that they are both feasible for real life, with the second approach prevailing first in time and money cost. [PERSON] et al. [40] proposed VANET, a privacy-preserving system that uses multi-level blockchain-based on clustering. Their proposal consists of vehicles and Authentication Centres. Moreover, the system is based on 5G wireless networks so the use of RSU is not needed. The Authentication Centres are divided geographically; there are the locals (LAC) and a global (GAC) consists of all the LACs. The LACs keep a blockchain ledger with the registered vehicles in their region and the GAC maintains a blockchain ledger with all the registered vehicles. The system, to preserve the privacy of the vehicles, firstly needs to physically verify the vehicle by LAC and impute it with a private key. This private key is used as a pseudonym for information exchange on VANET. Moreover, the vehicles are divided into two categories, the General Vehicles (GVs) and Emergency Vehicles (EVs) such as ambulances. In order to preserve location privacy the vehicles moving at the same direction form a cluster. When an EV enters the cluster it can use the system to transmit an emergency signal and notify the other vehicles in order to provide it with safe passage. The network is based on Ethereum and simulation experiments that have been contacted on the Truffle suite, showing the proposed system is feasible.