## 4 Implementation and Discussion
### Implementation Environments  
The evaluation of the proposed system's feasibility is detailed in this section. Table 3 presents the deployment context, framework, requisite technical resources, and software components. To develop the proposed system, various tools are employed to model the processes among the entities in the vehicular network. We utilize the off-chain and on-chain environment that is illustrated in Figure 8. In this case of an off-chain environment, we use Omnet++ and SUMO to simulate the VANET authentication protocol, and to generate the authentication messages. Omnet++ is utilized in our experiment as a tool for modeling and simulating discrete systems [28]. The design of the vehicular network uses NED language, combined with VEINS and INET frameworks. VEINS is an open-source framework designed for vehicular network simulations, utilizing OMNeT++ and SUMO [29]. The INET Framework serves as an open-source model library for OMNeT++, providing various protocols and models for communication networks [30]. The setup of vehicle nodes, as well as the creation of maps, junctions, and routes, are achieved through the use of SUMO [31]. After generating the authentication messages are sent to the on-chain environment. In the on-chain environment, we run the blockchain and set the solidity code for the smart contract. In our experiment, we use Truffle and Ganache in the on-chain environment. Truffle constitutes a comprehensive development \begin{table}
\begin{tabular}{c c} \hline \hline
**Software** & **Configuration/Version** \\ \hline OS & Windows 11 22 Hz 64-bit \\ CPU & AMD Ryzen 7 5800U CPU @ 1.90 GHz \\ RAM & 16 GB \\ Truffle & 5.11.0 \\ Ganache & 27.1 \\ Omnet++ & 6.0.2 \\ SUMO & 1.4.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Implementation environment. Figure 7: Handover signaling procedure. environment designed specifically for the Ethereum blockchain, offering an array of tools that facilitate the construction, evaluation, and deployment of smart contracts [32]. Ganache is the Ethereum development tool to simulate a blockchain environment locally and to conduct tests on the deployed smart contracts [33]. The relevant parameters that are considered for the experiment are detailed in Table 4. The communication model that we used is the IEEE 802.11p standard [34] that is specifically designed for vehicular environments, supports vehicle-to-vehicle and vehicle-to-infrastructure communication, and is compatible with Dedicated Short-Range Communication (DSRC).The simulation area we used is 5000 m \(\times\) 2500 m, which is located in two different areas with a scale of 1:20,000. In scenario 1, which represents a suburban area, we considered the geographical area near Okayama University, Tsushima, Japan. The initial creation of entities in the first stage comprises 100 vehicles, 4 RSUs, and 1 TAS, which functions like a Kerberos server. In scenarios 2 and 3, which represent an urban area, we used an area near Okayama Station that has higher vehicle density. Scenario 2 includes 1 TAS, 200 vehicles, and 8 RSUs. Scenario 3 contains 2 TASs, with the same number of vehicles and RSUs. We chose a communication range of 1000 m for the RSUs to allow broader coverage with fewer RSUs, and this range is often used as a standard in VANETs that aligns with typical ranges used in the IEEE 801.11p standard. The communication range of the vehicle that we used is 100 m, which provides reliable communication without excessive interference. The data rate set in the simulation is 27 Mbps, which aligns with the capabilities of the IEEE 802.11p standard. The safety messages are sent every 30 s to reach a sufficient update rate for traffic and hazard information. The mobility that we used in the simulation is the Duaroute Mobility as a standard mobility that is used in the IEEE 802.11p standard. Duaroute calculates routes for vehicles based on demand and network conditions. It generates routes by considering factors like road networks, traffic lights, and traffic density.