# Distributed Reputation for Accurate Vehicle Misbehavior Reporting (DRAMBR)
## 2 Background and Foundations
### Misbehavior Report (MR)  
In vehicular networks, the exact format of an MR is not yet fully defined. However, the ETSI standards provide a structured framework for securely reporting malicious activities. The MR format, as outlined in the guidelines of TS 103 759-V2.1.1-ITS [16], ensures the confidentiality, integrity, and authenticity of the data through encryption and digital signatures. This approach guarantees that reports of misbehaving vehicles are securely transmitted and verified within the network, helping to maintain the trust and reliability of the system.  
Once misbehavior is detected, the vehicle has the opportunity to signal the misbehavior by sending an MR later to the RS. The generated MR contains critical information stating the suspicious and related messages, a linked PC, a description of the misbehavior type, as well as the reporter's PC and the corresponding signature from the time of report creation. Figure 5 shows the structure of the MR format, as specified in ETSI, ITS.  
Table 1 illustrates the structure of the MR.  
\begin{table}
\begin{tabular}{c l} \hline \hline
**Layer** & **Description** \\ \hline Encryption: & MR is encrypted using ECIES with the MA public key, \\  & ensuring data confidentiality. \\ \hline Digital & MR includes a signature from the reporter’s private key \\ Signature & to authenticate the source and maintain data integrity. \\ \hline ToBeSignedData & Contains essential information like the report’s hash and \\  & signature, which are signed by the reporter. \\ \hline Payload & \
\begin{tabular}{l} Holds metadata and headers for proper interpretation of \\ the signed data. \\ \end{tabular} \\ \hline Core Data &
\begin{tabular}{l} Contains the unencrypted misbehavior data, including \\ the report’s hash for integrity verification. \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table}
Table 1: Misbehavior Report Structure.  
Figure 5: Misbehavior report format. Source: [16].  
The preceding explanation of the MR structure sets the stage for discussing the functional requirements of the MR as defined by the IEEE Std 1609.27\({}^{\text{m}}\)[17]. These requirements should be achieved to ensure the secure and effective collection of the reports.  
* The MR format shall be flexible to allow for any updates from other vehicles.
* The identities of both the reporter and the reported (target) vehicles should be included in the MR.
* Each MR must include evidence, such as the original received message and any relevant observations from other vehicles, which enables the MA to independently verify the MRs.
* To avoid overloading the transmission channel, each reporter is limited to submitting only one report for each vehicle at a specific time.  
In addition, the following security and privacy requirements have to be met:  
* Privacy protection: To avoid linkability, vehicles should rely on the PC so that the MA cannot link the short-term and the long-term identities of the reporters and reported vehicles.
* Authentication and integration: To ensure the authenticity and integrity of the exchanged information, each MR should be signed with the private key corresponding to the verification public key of the reporter.
* Confidentiality: Each MR should be encrypted to protect the confidentiality of the information sent to the MA.
* Non-repudiation: To allow the MA to verify the misbehavior, the MR should provide sufficient evidence, including the suspicious messages and the associated pseudonyms.