# Decentralized Documentation of Maritime Traffic Incidents to Support Conflict Resolution
## 2 Background
### Approaches to Immutable and Decentralized Data Storage  
Establishing trust between different parties that have no direct trust relationship but aim to exchange information with each other is not a new problem in communications engineering. Typical setups for the exchange of digital information start with the authentication of the involved parties with the help of an identity provider. Therefore, a relying party can identify other participants by trusting the identity provider [11]. However, authentication of a party does not imply full trust in the actions of that party. In the maritime industry, it may be easy to identify a vessel or infrastructure with the help of its registration data at the IMO via an MMSI or even digitally via Identity Providers that connect vessel identities to digital certificates such as the Maritime Connectivity Platform (MCP) [12]. However, when it comes to trusting the correctness of a data asset that was recorded by a specific entity, additional frameworks need to be introduced. As discussed in Section 1, for accident investigation data, it is crucial to ensure that the data were recorded at the time of the accident and not subsequently modified. In similar situations, where the different participants do not trust a common central entity that could guarantee the correctness of the exchanged data, blockchain technology has often been applied.  
A blockchain is a specific type of distributed database that only allows the addition of new information if a consensus in the network of involved participants is reached. Furthermore, data is only being added to the blockchain in the form of atomic transactions, which are organized in a chained data structure referencing its respective predecessor. After a transaction is issued, it is impossible to modify it, which is referred to as immutability [13].  
However, the inflationary usage of blockchain technology in all possible use cases has been questioned more and more recently [14; 15]. Also, there are other less complex solutions to the problem of providing proof that data existed at a certain point in time and was not modified. For instance, a possibility of this kind in regard to timestamps is represented by so-called timestamping authorities [16; 17]. A TSA is a service that establishes that some data existed at the specified time based on reliable time sources and cryptographic signatures. Depending on the application, such a TSA can be operated in-house or externally, either as a commercial service or as a service for third parties.  
The biggest problem in using these services is that all parties must trust the selected TSA [18]. Suppose one party can obtain the private key or manipulate the TSA's internal system time. In that case, the entire chain of evidence is invalidated since the data can then be signed with different timestamps. To circumvent this, an approach based on \"distributed trust\" is presented in [19] by randomly selecting subsets from a set of TSAs via a pseudorandom number generator (PRNG). However, even in this case, users of TSAs must always rely on the availability and proper functioning of the TSA they are using to sign (similar to trusting a certificate authority in a PKI).