# Privacy-Preserving Solutions in Blockchain-Enabled Internet of Vehicles
## 6 Privacy-Preserving Blockchain-Based Solutions
### Traffic Conditions  
Another important service of VANET is the monitoring of traffic or road conditions in order to improve the performance of the road circulation and avoid accidents. The following papers suggest several systems which purpose is to upgrade road conditions while protecting privacy. [PERSON] et al. [41] suggested CreditCoin, a system for announcement exchange in VANET. It develops a custom announcement protocol by the name \"echo-announcement\" and a permissioned blockchain network based on coin-exchange system for reliability and privacy. The key entities of CreditCoin are a Trusted authority (TA), which is responsible for managing the cryptography keys and user identity, the Trace manager (TM) to trace malicious users, users which are vehicles and On-Board Units (OBUs), Roadside Units (RSU), which are distributed alongside the roads and are responsible for the users inside their communication range and lastly, a cloud application server for non-cryptographic data exchange. The main idea of the system is that a user can broadcast in the network via the \"echo-announcement\" protocol, reliable information about the traffic and the receivers are able to take advantage of these information in order to make route changes. The blockchain network is based on coin-exchange logic for every valid announcement. Every user starts with a few coins in order to broadcast an announcement and a threshold ring signature of this announcement, for example a car accident, which nearby users must confirm and then RSU with official public vehicles take the role of the consensus server which creates the coins. Thus, there is not a need for a work-of-proof, instead a byzantine fault tolerance consensus algorithm is used and by taking advantage of combined-public keys (CPK) for reducing cryptographic time consumption, the transactions are fast. The confirmed announcement is signed by the nearby users and broadcasted in the whole network. As a result, the user is earning coins and reputation. A false announcement costs coins and for that reason, the network can be protected from malicious users. Moreover, to avoid attacks to user's wallet, the coins and the reputation have time limitation for their use. If any misconduct was found, the trace authority Pseudonym Management sends the information to the cloud application to take actions. The proposed system had been tested thoroughly in PolarSSL simulation environment and the results have shown that privacy can be sufficiently preserved. [PERSON] et al. [42] suggested a blockchain-based warning scheme which aimed to solve traffic problems. This system is using a group signature-based authentication protocol in combination with blockchain technology, to guarantee privacy and security and parallel to ensure identity traceability. In contrast to traditional methods, where the status information of vehicles is acquired by the on-board diagnostics and the position data through the GPS sensors, the proposed system is using a smart terminal (for example a smartphone) to collect those data, through some adjustments and assumptions. Such assumptions are that a normal turn takes 5 s and a sharp turn takes 3 s. Furthermore, x and y axis of the terminal simulate the acceleration and angular velocity respectively. The irregular noise that may occur can be eliminated using a weighted moving average filter. The collected data is sent to the feature recognition module for driving behaviour identification. Detecting irregular driving can warn the driver early for possible accident. An edge node within the group is served to Group Managers which create a pair of public and private keys and broadcast the public and parameters to in range vehicles. The vehicle applies a blind signature and submits its authentication information back to the manager. Finally, the vehicle communicates with nearby vehicles through the edge node, having signed the status information through certificate and group public key.