[9], providing sufficient transparency to the concerned actors (like the clients) regarding the flow of money at different stages of the construction [10].
2.2 Prerequisites
Corda is a platform provided by R3 which is an open-source distributed ledger technology and it is known for handling complex transactions including the fact that it restrains access to the transaction data [11]. This platform terminates the need for third-party intermediation and the need for all the nodes on the Corda network to have data about every transaction, unlike other blockchains, where this data is accessible by all the nodes of the network [12]. Corda is used by many businesses, like financial and medical institutions to keep a shared ledger of transactions [13]. It is to be noted that Corda has many benefits of a blockchain, but it is not a blockchain [14]. This is more similar to Hyperledger Fabric [15] and Quorum [16] when compared to Ethereum [17] and Bitcoin [18]. The practice of using distributed ledger technology over blockchain discards the additional effort and time that networks waste to keep data consistent amongst all nodes. Another point to be noted is that people assume that “blockchain” [19] and “distributed ledger technology” [20] are the same and end up using these terms interchangeably.
2.2.1 DLT vs Blockchain
In DLT, the distributed ledger is more like a shared database that is spread over all the participants or nodes of the network, where their identities are known and verified [21]. Every node makes an identical copy of the ledger and saves it, therefore, updating itself independently [22]. One of the salient features of the distributed ledger technology is that this shared ledger is not monitored by a central authority [23]. Instead, the updates on the ledger are built and recorded independently by every node [24]. Once the nodes reach a consensus [25] with the help of a consensus algorithm, the ledger [26] automatically updates itself and the most recent version of the ledger is saved on each node independently. The architecture of distributed ledgers helps in reducing the cost of trust remarkably [27].
Blockchain technology is a significant use case of the distributed ledger technology [28]. A blockchain is distributed across and managed by decentralized, peer-to-peer networks [29]. Most of the time, all information [30] stored in a blockchain is visible to all the nodes in the network and these nodes may be anonymous. The architecture [31] of the blockchain makes it stand out from other kinds of distributed ledgers as the data on a blockchain is grouped and organized in various blocks [32], which are then securely linked to each other by cryptographic principles [33, 34]. Hence, a blockchain can be termed as a collection of continuously growing records that are immutable and secure [35]. Therefore, it can be said that every blockchain is a distributed ledger, but every distributed ledger doesn’t need to be a blockchain.
The similarities between a blockchain and a distributed ledger are that both of them use public and private key cryptography, i.e., both the technologies use the concept of hashing [36]. Also, both of them make use of the peer-to-peer model for communication between nodes. Any transaction made in either of the technologies is permanent. No central authority has control in both the technologies, making them decentralized [37]. The differences between these technologies are listed below (See Table 2.1) [38].
Table 2.1 DLT vs Blockchain.
| DLT | Blockchain |
| DLT doesn’t require a currency. | Blockchain requires a currency. |
| The data is not revealed to all nodes. | The data is visible to all nodes. |
| DLT is not permission-less. | Blockchains are permission-less. |
| All the nodes are verified before entering into the network. | All the nodes are verified before entering into the network. |
| The consensus is pluggable at the transaction level. | The consensus is the same across the entire network. |
| Miners are not required in this scenario. | Miners are required in this scenario. |
| Legal prose can be attached. | There is no scope for the legal standing of any transaction. |
| The data is not stored in blocks. | The data is saved in blocks that are linked to each other. |
2.3 Key Points of Corda
R3 Corda is a collective endeavor that began in September 2015 between R3 and numerous banks and financial groups for creating a framework which is more than a conventional blockchain [39]. Corda is specially designed to deliver qualities such as quickness, privacy, scalability, and security. In terms of architecture, Corda is a DLT and not a Blockchain. Nevertheless, Corda has all the features like distribution, decentralization, fraud-proof, append-only, immutability, etc. that are offered by a blockchain [40]. Before proceeding any further, there are certain key points about Corda that one should know to have a better understanding of the solution:
Corda is a private and permissioned blockchain where the entry of nodes into the network is done over a network map service called the “doorman”. Here, every node is a verified IP address that undergoes a rigorous KYC process before being accepted into the network. Wherefore, nodes have their legal name, IP address, and X.509 certificate that is signed by the doorman [41].
The communication between the nodes is point-to-point with Transport Layer Security encrypted messages over AMQP. Therefore, only nodes with a genuine need-to-know requirement can see the data within an arrangement [42].
Transactions are considered as a proposal to update the ledger provided there is no double spend [43].
The UTXO (unspent transaction output) model wherein a transaction can have inputs and outputs ranging from zero to any number is used in Corda [44].
The transactions in Corda are validated by notaries as well as parties related to the transaction instead of a broader pool of unrelated validators.
The consensus in Corda has two aspects, namely: transaction validity, where the contract code that executes the transaction is checked and it is made sure that all the required signatures along with any referenced transactions are valid. The second aspect is transaction uniqueness where it is made sure that the respective transaction doesn’t lead to a double-spend by making sure that there no similar transaction exists [45].
There are certain special nodes in Corda, termed as notaries that can get involved in the transactions for validating them and terminating double-spending.
Multiple notaries are present in a Corda network, preventing a single point of failure.
The ledger is subjective from each peer’s perspective as no transaction is broadcasted to the entire network unless required. Each transaction is visible only in the ledgers of the peers that were involved in the transaction and no one else [46].
A minimum of two peers is always assured to see the same version of any on-ledger facts that they share.
2.3.1
