# VANET Secure Reputation Evaluation & Management Model Based on Double Layer Blockchain
## 3 Basic Concept and Initial Settings  
### System Components  
Firstly, we clarify our purpose again: to design a blockchain-based reputation management model that includes reliable updates, secure storage, and query of node reputation. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Reference**} & \multirow{2}{*}{**Decision Logic**} & **Reputation** & **Anti-Attack** \\  & & **Characteristics** & **Capability** \\ \hline
[14] & BI & I & Single Class \\
[15] & BI & I, H & Several \\
[16] & BI & I & Single Class \\
[37] & Simple weighting & I & Single Class \\
[38] & Simple weighting & I & Several \\
[39] & 3 VSL & I, H & Single Class \\
[42] & Multi-weight fusion & I & Single Class \\
[43] & Simple weighting & I & Several \\ DBREMM & Multi-factor BI & L, H, S & Several \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of the related works. The goal is to measure the reliability of vehicles in VANET through reputation, so as to ensure the safe transmission and sharing of data. The secure scheme designed in this paper is based on a typical VANET network model, and we re-designed the model to suit the DBREMM framework under the data verification scenario. The framework is divided into four layers, from bottom to top, including a vehicle layer, network layer, blockchain layer, and superstructure layer. The system components include vehicle nodes, roadside units (RSUs), blockchains, superstructure, etc. These mobile nodes and infrastructure communicate with each other through communication methods, such as DSRC (dedicated short range communication), LTE (long term evolution), 4G, 5G, and beyond to achieve data sharing. The connection mode of each component is shown in Figure 1, and the detailed description of the components is as follows. **Vehicle layer and network layer**: _Vehicle node_: Vehicles are equipped with an on-board unit (OBU), including advanced communication devices, wireless transmission modules and trusted execution environment (TEE). Vehicles are capable of communicating with other vehicles and RSUs, and have rational computing power to perform simple calculations. Calculations include detecting and reporting various road condition events and calculating the direct and indirect trust of targets based on received data. Meanwhile, vehicles can participate in a blockchain consensus as well as query the content on the blockchain. Any vehicle node has the possibility of breaking down or being controlled by an attacker. _RSU_: RSUs are responsible for helping establish communication between all vehicle nodes under their coverage. They have sufficient computing power, network communication capabilities, and storage space, and they are well equipped with TEE. As the relay station of vehicle nodes and superstructures, the RSU is responsible for event collection and  
Figure 1: Overview of the DBREMM. reporting, reputation update and management, and the coordination of block production of the event chain and reputation chain. **Blockchain layer**: In DBREMM, there are two consortium blockchains used collaboratively, namely the event chain and the reputation chain. RSUs and some of the vehicles with spare computing power are pre-selected to participate in the consensus. As consensus in the consortium blockchain is based on votes, which means that in the consensus process, a branch of nodes verifies the content of the block and vote. It requires less computing power compared with computational proofs, such as PoW. Upon completion of registration, each vehicle node and RSU can keep a ledger of the consortium blockchain separately (in part or in whole, depending on the node's computing power), and any user can view non-private information on the chain and access services. **Superstructure layer**: Including all kinds of infrastructures, application platforms, etc. In our model,it mainly includes:  
_TA_: TA (trusted authority) is the superstructure facing the reputation chain. Its main responsibilities include two parts: first, initialization of the system.