## 5 System Construction
### System Setup
Figure 4 shows the overview of the attack scenario within the proposed system. The system is secure against DDoS and Eclipse attacks as the unregistered nodes have been treated as malicious nodes that can try to communicate with registered nodes using their signature. Since the signature is generated as \(\sigma\) = (\(\pi\mid\mid\) SK \(\mid\) T)\({}^{\text{PK}}\) and only registered vehicles can compute the secret proof '\(\pi\)', this means an incomplete signature is sent from the malicious node to the registered node. The receiving node can easily identify the incomplete signature and report the malicious node to the nearby RSU who can block its activities from the network. The same may happen with RSU if any malicious node tries to send malicious data to the RSU, but because of an incomplete signature, its messages are not going to be delivered. Tracing malicious nodes can be effectively achieved by identifying unregistered and unauthenticated nodes trying to communicate with other nodes within the network, thus satisfying the third and fourth design goals. #### 6.2.1 Average Packet Delay Ratio

Average packet delay is the time taken by a packet to reach to its destination from the source. Figure 5 shows the results of an average packet delay ratio in the presence of a DDoS attack. Figure 5a shows a steady average packet delay in the presence of a DDoS attack with respect to the number of nodes as opposed to Bilinear Pairings [46], Secure Trusted-based Blockchain [25], and Hybrid Approach [47]. Figure 5b shows the average packet delay ratio in the presence of a DDoS attack with respect to time. It can be observed from both Figure 5a,b that the proposed system brings steady or minor changes in the average packet delay ratio in contrast with others. Figure 4: Overview of the Attack Scenario within Proposed System. #### 6.2.2 Verage Packet Loss Ratio

Packet loss is the proportion of packets lost/dropped against total packets sent in the network. Figure 6a shows that the proposed system suffers from less average packet lost in the presence of a DDoS attack with respect to number of nodes and Figure 6b with respect to time as opposed to Bilinear Pairings [46], Secure Trusted Blockchain [25], and Hybrid Approach [47]. With the increased number of nodes, the efficiency of the one-time zero-knowledge proof generation scheme in the proposed system makes the packet loss ratio go steady. #### 6.2.3 Average Packet Delivery Ratio

The number of packets successfully delivered to the destination to the total number of packets sent is known as the packet delivery ratio. Figure 7a shows that the packet delivery ratio is higher in the proposed system in the presence of a DDoS attack with a slight decrease as the number of nodes starts increasing from 50 to 90, but becomes steady when the number of nodes continues, increasing further in contrast to other proposed architectures. Figure 7b shows the Average Packet Delivery Ratio in the presence of DDoS with respect to time. Figure 5: (a): Average Packet Delay with DDoS Attack w.r.t No. of Nodes; (b): Average Packet Delay with DDoS Attack w.r.t Time. Figure 6: (a): Average Packet Loss Rate with DDoS Attack w.r.t No. of Nodes; (b): Average Packet Loss Rate with DDoS Attack w.r.t Time. Figure 7: _Cont._

#### 6.2.4 Average Delay with Eclipse Attacks

The proposed system has been evaluated for its performance against an Eclipse attack on the blockchain structure. Figure 8a shows an average packet delivery delay in the absence of an Eclipse attack and Figure 8b shows an average packet delivery delay in the presence of an Eclipse attack. From Figure 8b, it is observed that there is a slight delay in the packet delivery when an Eclipse attack is launched against blockchain but the difference is minor. Figure 8: (**a**): Average Delay without Eclipse Attack; (**b**): Average Delay with Eclipse Attack. Figure 7: (**a**): Average Packet Delivery Ratio with DDoS Attack w.r.t No. of Nodes; (**b**): Average Packet Delivery Ratio with DDoS Attack w.r.t Time.