## 2 Background and Related Works
### Architectural Considerations  
Blockchain is a type of peer-to-peer (P2P) distributed network of independent participants that generally broadcast all data to each other, each of whom may have different motivations and objectives. They may not necessarily trust one another but reach a _consensus_ (a consistent agreement about changes to the state of the shared database) on a linear history of operations of that shared database. On the other hand, _permissioned_ or _private_ refers to blockchains where access is restricted to a specific set of vetted participants. These blockchains operate in an environment where participants are already known and vetted and there is a level of trust among them. Participants are held accountable through off-chain legal contracts and agreements and are incentivised to behave honestly via the threat of legal prosecution in the case of misbehaviour. In the landscape of blockchain technologies, two significant frameworks stand out due to their distinctive approaches to security, privacy, and scalability: Bitcoin [10] and Corda [11; 12; 13].  
_Bitcoin's Architecture_. Bitcoin [10], the pioneer of blockchain technology, utilises a decentralised, peer-to-peer architecture to facilitate digital transactions without the need for a central authority. Its design is centred around the concept of a fully public ledger, which records all transactions across all network participants in a transparent and immutable manner. This ledger, or blockchain, is maintained by a _consensus mechanism_ known as Proof of Work (PoW) [10], which requires miners to solve complex computational puzzles to validate transactions and create new blocks. Furthermore, although Bitcoin's architecture ensures the anonymity of all participants in the network and full transparency, it does face challenges with transactional privacy. Every participant has access to the entire transaction history, which raises concerns about privacy, together with the addition of the issue of scalability. This process ensures the integrity and security of the network but also introduces challenges such as high energy consumption and scalability limitations due to the time and computational power required to process transactions.  
_Corda's Architecture_. Corda, on the other hand, adopts a more tailored approach, as it is designed as a _permissioned_ blockchain platform, focusing on the needs of businesses, particularly in the financial sector [11; 14]. It enables direct point-to-point messaging to guarantee private transactions, ensuring transactional data remain confidential between parties involved with verified identities, thus addressing the privacy concerns inherent in public blockchains like Bitcoin [14]. Although it is not a traditional blockchain because it does not maintain a global ledger of all transactions, it is still a DLT, enabling businesses to transactdirectly and privately with each other, thereby minimising unnecessary data sharing [12; 14]. Instead, it allows only the parties involved in a transaction and those with a need to know to access the transaction's details. This is achieved through the use of Corda's \"Flow Framework\" for transaction processing, which facilitates direct communication between parties and complex transactional workflows [11]. Corda records transactions in individual \"vaults\"--\"Transaction Vaults\"--that are crucial for maintaining this transactional privacy while allowing traceability for compliance and transparency [11; 12; 13]. Furthermore, Corda's design supports the development of \"CorDapps\" (Corda Distributed Applications) and the design and implementation of a wide variety of \"smart contracts\" that can be customised for various financial services, ensuring compliance and offering scalability and privacy [12] that the Bitcoin network cannot directly provide.