# Decentralized Documentation of Maritime Traffic Incidents to Support Conflict Resolution
## 5 Application and Evaluation
### Application and Results
Therefore, the Port Operator broadcasts TSA1 and TSA2, the VTS Operator broadcasts TSA3, and the Berthing  
Figure 8: Geographical region in front of the quay wall where a documentation process is initiated when a vessel enters (Cuxhaven, Germany). Vessel TSA4 and TSA5. After receiving messages from all other participants, the participant can determine the intersection of the trusted TSAs locally. In iteration \(j=1\), the intersection is an empty set, so another iteration is initiated along the negotiation protocol. * Iteration \(j=2\): In the second iteration, participants are requested to expand their list of trusted TSAs. Therefore, the VTS Operator and the Berthing Vessel include the TSAs of their trusted entities. The VTS Operator trusts the BSH. Based on private relationships or the use of the Public Trusted Entities Repository, the VTS Operator knows which TSAs are trusted by the BSH. In this case, the BSH trusts TSA1 and TSA2, so they are included into the VTS Operator's TSA list. The Berthing Vessel relies on the DLR and the IALA. The DLR trusts TSA6 and the IALA trusts TSA7. Therefore, both TSAs are also included in the list of the Berthing Vessel. The Port Operator follows a very strict strategy and trusts only his own two TSAs. There is no extension of the list at all. Afterwards, every participant broadcasted their trust list and it is checked again whether a common intersection exists between the participants. After iteration \(j=2\), the intersection at TSA is still empty, so the next iteration is initiated. * Iteration \(j=3\): In the third iteration, only the Berthing Vessel is further expanding its list of trusted TSAs. For this purpose, the Berthing Vessel relies on the trusted TSAs of the trusted entities from the DLR and IALA. Therefore, TSA1 and TSA2 are also added to the trust list of the Berthing Vessel. The VTS and Port Operators are not expanding their trust list. Again, the intersection of all trust lists is determined locally. In the iteration, the participants find a common basis with TSA1 and TSA2. This fulfills the condition \(\cap_{i=1}^{n}\tau_{i}(P_{i})\
eq\varnothing\), so the negotiation protocol terminates at this point. The participants can use either TSA1 or TSA2 to sign their data. If no common TSA has been found at this point, it would not be possible to find a common TSA for all participants, since all participants have already extended their lists to the maximum (\(j_{\max}=3\)). In this case, an attempt would be made to find a common TSA for as large a subset of participants as possible (c.f. Figure 4, left part). Record the data: After agreeing on a common set of TSAs, no further communication takes place over the P2P network. Instead, each participant records their data analogously to the process of Figure 5 by chunking the data in 10-s intervals and hashing it with SHA256. Each participant then sends the hashes directly to one of the determined TSAs. In our application, the Port Operator and Berthing Vessel used the TSA1 and the VTS Operator utilized TSA2. Finally, the data chunks of the data stream are persisted in the local recording database together with the signature of the TSA. Only in case of an actual conflict, e.g., the Berthing Vessel damages the quay wall, the signed records are retrieved from the databases as proof of the actual course of events. In this case, the Port Operator and the VTS Operator would disclose their data to show that the Berthing Vessel damaged the quay wall. In addition, the participants can verify, with the process described in Figure 2, that the data already existed during the berthing maneuver. Since the Berthing Vessel also trusts the signing TSA, it cannot deny that the data has been manipulated afterwards by the Port or VTS Operators. Of course, the Berthing Vessel can also provide its own signed data in order to exonerate itself. In general, a large and heterogeneous data foundation helps to reconstruct the real course of a berthing maneuver.