## 3 V2X System Architecture When Integrating Blockchain Technology and MEC
### Application of Blockchain Technology between Road Users and RSUs  
In the case of V2X, promising blockchain technology can be used to manage information trustworthiness, as event information would be stored in a publicly accessible blockchain. This technology can be applied in a variety of circumstances, such as the reliable transfer of information between network objects, the assessment of a road user's rating and credibility with high node mobility.  
Blockchain can solve major problems faced by V2X systems and provide security for the distribution of critical information. Using blockchain to reliably transmit information is important when transmitting and avoiding loss or distortion that could lead to negative consequences. Blockchain technology relies on rules and concepts to avoid these consequences. Due to the design of blockchain trust management, it can be successfully applied between nodes with decentralized systems.  
Malicious nodes can infiltrate the network and spread false information on the network, causing the transport network to fail. Using blockchain to rate a road user is also an effective solution for use in the V2X system, as rating a facility would allow action to be taken against offenders and encourage decent users. This would ensure that misbehavior messages that create risk or reduce the efficiency of the V2X system are reduced.  
The use of algorithms on trust management and separation of priorities allows traffic participants to determine, with high probability, whether the received message is reliable. Thus, for objects with a high reputation rating, the information would be accepted faster, since the quality of the data depends on the reputation of the object. The trust value of the network participants is determined based on the scores obtained from past behavior, which are attached and stored in the system using blockchain technology. Thus, two parameters would be used in messaging--first, the event information itself and, second, the priority of the message based on the service category and on the reputation of the object (rep). This method would allow a more objective perception of the real situation to be obtained, encourage users to behave decently and consistently record events for further processing and use.  
To organize this process, the authors propose to use blockchain with the Practical Byzantine Fault Tolerance (PBFT) consensus algorithm, which is responsible for efficient  
Figure 1: The architecture of the proposed system.  
operation in asynchronous networks, allowing consensus to be reached even if some nodes in the network do not respond or give wrong information. This algorithm involves selecting two types of nodes--leader and backup nodes. Each node in the network maintains its own internal state and, when it receives a message, it performs calculations and prepares a decision on the newly received message. The individual decision of each node is sent to the node leader, who confirms the credibility of the new message based on the decisions of all nodes. The leader in our system is proposed to use the RSU, while the redundant nodes are traffic participants connected to the V2X system.  
The procedures for calculating, verifying and storing a blockchain-based trust score are shown below.