# Distributed Reputation for Accurate Vehicle Misbehavior Reporting (DRAMBR)
## 4 System Model
### Workflow and DRAMBR Phases
#### 4.4.2 Process 2: Online Reporting (OR)
RS Process: The RS in our system is a centralized entity that collects MRs from reporters, decides on the suitable reaction to make, and evaluates their credibility to determine the reputation scores and forwards verified MRs to the MA for further action; Figure 10 illustrates the OR process. We defined three main functions of the RS: * MR Grouping and Structure: The RS collects all the MRs and then adds them to its database. This step would enable access to MRs using specific criteria. For instance, the RS can get all the MRs associated with a certain pseudonym or all the MRs from a specific area. Those requests could be helpful in the analysis phase. Additionally, the RS filtering system aggregates similar MRs, such as those showing speed inconsistencies. * MRs Analysis and RS Actions: The RS analyzes the MRs to output the correct reaction. Correct MRs mostly align with a \(Rep_{\text{Vehs}}\) past behavior and match the majority consensus, while \(MR_{f}\) often deviates from or contradicts these patterns. Since setting the event ground truth in offline communication is challenging without the infrastructure to confirm the event. The RS establishes the event baseline using the Density Based Spatial Clustering of Applications with Noise (DBSCAN) in its initial classification, which is based on dense regions of consistent MRs with confidence determined by the \(Rep_{\text{Vehs}}\) RV to ensure reliability. Once the ground is established and the DBSCAN clusters are formed, the RS applies the iForest to detect any anomalies within the DBSCAN outputs further. This step ensures the flagging of the potential \(MR_{f}\). Furthermore, RS implements the GMM predictions for the accurate classification of honest, malicious, and erroneous reporters to refine the categorization of MRs in order to enhance the classification accuracy. The technical aspects of these steps are discussed in Section 5. Table 5 outlines the classification of how incoming MRs are evaluated for potential misbehavior \(Rep_{\text{Vehs}}\) based on various inconsistencies. * RS Decision: We propose a simple threshold method for the RS to trigger reaction levels based on a flexible MR count. While an accurate misbehavior reaction is still a debated subject in the ITS, we propose three levels of RS reaction for both the \(Rep_{\text{Veh}}\) and \(Tar_{\text{Veh}}\) as shown in Table 6. * \begin{table}
\begin{tabular}{l l l} \hline \hline
**Class** & **Purpose** & **RS Action** \\ \hline
1 & Implausible MR values. & Checks if the MR values are realistic. \\ \hline
2 & Consistency checks with previous MRs. &
\begin{tabular}{l} Compares an MR with earlier ones from \\ the same \(Rep_{\text{Veh}}\). \\ \end{tabular} \\ \hline
3 & Validation against local knowledge. &
\begin{tabular}{l} Checks the MR against the vehicle’s map \\ or local data. \\ \end{tabular} \\ \hline
4 & OBUs-based MR validation. &
\begin{tabular}{l} Compares the MR with the vehicle’s \\ own sensors. \\ \end{tabular} \\ \hline
5 & Cross-MR consistency analysis. &
\begin{tabular}{l} Checks if the MR agrees with other MRs \\ for the same event. \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 5: \(MR_{f}\) Classification. * Blacklist and Penalty Enforcement: Potentially misbehaving vehicles (\(Rep_{\text{Veh}}\) and \(T_{\text{Veh}}\)) will be reported to the MA. If the RV drops below the pre-set threshold, the RS develops a detailed MR and sends it to the MA within the SCMS. The MA decides on the seriousness level of the low RV and utilizes misbehavior detection algorithms to assess the situation and notify all participants regarding the detected misbehavior in two stages of reaction: 1. Passive revocation: The \(T_{\text{Veh}}\) is blocked from requesting new certificates and \(Rep_{\text{Veh}}\) is temporarily suspended from reporting privileges. 2. Active revocation: The \(T_{\text{Veh}}\)'s certificates will be revoked, and it is then sent to the CRL. The \(Rep_{\text{Veh}}\) will be permanently banned from submitting MRs.