## 2 State of the Art  
### Blockchain and Smart Contracts  
Most prominently, blockchain is known as the technical infrastructure behind cryptocurrencies such as Bitcoin or Ethereum. Blockchain, as a well-known form of Distributed Ledger Technology (DLT) [21] is a technology for providing a tamper-proof and easily verifiable transactional ledger system for storage and program execution. A blockchain groups these transactions into linked data blocks and makes the order and integrity of those blocks easily verifiable [22; 23]. This ensures a transparent and tamper-proof environment for exchanging values or executing program code via computer nodes connected to a blockchain network. Therefore, blockchain can be used to introduce a trustless and neutral platform for immutable data storage, exchanging information, saving executable code contracts, and automating payments [24; 25]. Blockchain technology is already used, e.g., to support traceability in supply chains [26] where several participants work together and transparency about the shipped goods, the origin of their materials, and immutable records of each handover represent very valuable information. Especially for international exchanges between participants from multiple jurisdictions, a global settlement layer for contracts that can be specified up front can increase the degree of automation and reduce friction [27; 28]. To ensure that only valid transactions are included in the blockchain, consensus mechanisms decide who may propose the next block and verify its included transactions. The most prominent consensus mechanisms are Proof of Work (PoW), Proof of Stake (PoS), and Proof of Authority (PoA) [29]. The PoW only allows the first computer node with proof of the correct solution to a computing-intensive puzzle to propose the next block. This procedure serves as the base for security, especially in public blockchains such as Bitcoin, but has the disadvantage of high energy consumption. In PoS, every node has to lock money in the form of cryptocurrencies inside the system, which replaces the need for costly puzzles and, therefore, solves the high energy consumption issue of PoW. The PoA describes a mechanism similar to that of PoS by replacing the validator's financial stake with its reputation, where the validator's identities are known inside the network and faulty behavior leads to a loss of trust. An established PoA mechanism is the Istanbul Byzantine Fault Tolerant (IBFT) based on the works of [PERSON] et al. [30], where an arbitrarily selected node can propose a new block, which is only accepted if a super-majority of all nodes confirm its correctness. This two-level validation provides a trade-off between performance and fault tolerance [31]. A blockchain that limits its access to a controlled user group to protect the information stored on the blockchain is called a consortium blockchain. This type of blockchain offers a trade-off by decreasing a blockchain's decentralization but improving scalability and performance. GoQuorum and Hyperledger Besu are well-known consortium blockchain implementations that still maintain compatibility with smart contracts developed for the public Ethereum chain [31; 32]. Smart Contracts (SCs), the software components executed on a blockchain, enforce programmed behavior without any possibility of changing the scripted rules after installation (i.e., \"deployment\") [23; 24]. The users can create and interact with smart contracts by sending a transaction to the blockchain. Once the transaction is evaluated, the data storage is updated according to the codified rules, and the new state is saved by each blockchain node. There are different degrees of decentralization for systems using blockchain technology, and it is not necessary (and, in most cases, not useful) to store everything on the blockchain or have all processes executed as smart contracts.