# CrossDeFi: A Novel Cross-Chain Communication Protocol
## 4 Preliminaries
### System Architecture  
Cross-chain technology enables seamless interoperability among various blockchain-enabled DeFi networks, facilitating asset transfers across different systems with diverse characteristics. This technology allows each blockchain within a multi-blockchain system to operate independently yet interact effectively through cross-chain strategies. These strategies permit seamless asset transfers, meeting the required specifications and thus enhancing the efficiency and performance of the combined DeFi systems. Cross-chain capabilities also allow multi-chain systems to offer greater scalability and interoperability compared to single-chain systems.  
A typical novel cross-chain structure across different DeFi systems is shown in Figure 1. It illustrates how different blockchain networks within the DeFi ecosystem interact using cross-chain bridges, how cross-chain smart contracts are utilized, and how DeFi users engage with each other.  
This section effectively describes the system model of CrossDeFi. Figure 1 explains the typical process of asset transfer across two distinct DeFi systems, DeFi X and DeFi Y, which utilize different blockchain models with various characteristics. These blockchains employ various smart contracts, consensus algorithms, assets, tokens, and bridges to enable DeFi services. For instance, DeFi X may use a Bitcoin type of blockchain, while DeFi Y might utilize Ethereum or Hyperledger Fabric technologies. The CrossDeFi protocol acts as a generalized asset transfer protocol where any user can be a source or destination for asset transfer. Apart from the users of DeFi X and DeFi Y, the miners play another crucial role in the system. CrossDeFi selects specific miners from both DeFi X and DeFi Y. The cross-chain asset transfer is performed among the selected miner nodes. The miner nodes in CrossDeFi further communicate with the specific users who initiate the asset transfer process, e.g., user X (UX) and user Y (UY) in Figure 1. If the asset is successfully transferred between X and Y, the miner node confirms the asset transfer to both users, DeFi X and DeFi Y. The CrossDeFi defines the system model's main components: DeFi user, asset, miner, and asset transfer confirmation.  
DeFi Users: In DeFi X and DeFi Y, users UX and UY initiate the asset transfer process. [PERSON] acts as the sender, and UY as the receiver, each belonging to different blockchains, DeFi X and DeFi Y, respectively.  
Asset: This is a digital representation on a blockchain in token form that can be traded with various types of currencies across different DeFi systems.  
Figure 1: A typical CrossDeFi architecture.  
Miners: The best miners (\(BMiX\) and \(BMiY\)) are chosen from the miner pools of DeFi \(X\) and DeFi \(Y\), respectively, based on consensus type and other characteristics. The best miner, \(BMiX\) from DeFi \(X\), is responsible for transferring the assets and confirming the successful asset transfer from the source to the destination. Highly trusted miners are mostly selected to participate in the transfer process.  
Successful asset transfer: This is the process of delivering assets from the source, DeFi X, to the destination, DeFi Y, with appropriate transfer confirmation messages. CrossDeFi considers factors such as asset support ability, transaction fees, security features, and community reputation in miner selection and chooses the most appropriate miners for asset transfer. Additionally, the miner of DeFi Y is responsible for generating irreversible new blocks to confirm successful asset transfers.