After years of research and development, we finally entered a multi-chain market. There are currently more than 100 active public chains on the market, many of which have their own unique applications, users, geographic distribution, security models, and design trade-offs. Although individual communities are unwilling to believe, the universe is entropy increasing, and the number of these networks may continue to increase in the future. This type of market structure requires interoperability between different networks. Many developers have realized this, and blockchain cross-chain bridges have exploded in the past year. At the time of writing, there are currently more than 40 different cross-chain bridge projects.

1 Interoperability releases innovation. As each ecosystem develops, they will develop their own unique advantages, such as higher security, faster throughput, cheaper transactions, better privacy, and specific resource supply ( Such as storage, computing, bandwidth) and regional developer and user communities. The reason why cross-chain bridges are important is that they enable users to access new platforms and protocols to achieve interaction, and allow developers to collaborate to build new products. More specifically, they can: Improve the productivity and utility of existing encrypted assets Cross-chain bridges allow existing encrypted assets to travel to new places and do new things. For example: Send DAI to Terra to purchase synthetic assets on Mirror or earn income on Anchor; Send TopShot from Flow to Ethereum to be used as collateral for NFTfi; Use DOT and ATOM as collateral to obtain on Maker The DAI loan allows the existing agreement to have more powerful product functions, and the cross-chain bridge expands the design space that the agreement can realize. For example: YFI liquidity mining on Solana and Avalanche; NFT on Ethereum and Flow's cross-chain shared order book on the Rarible protocol Let Index Coop launch the PoS index to unlock new features and use cases for users and developers to unlock new features and use cases for users. And developers provide more options. For example: Cross-DEX arbitrage transactions on Optimism, Arbitrum and Polygon (for example, Sushi) Use Bitcoin to pay for storage fees on ARweave Participate in PartyBid’s NFT group purchase on Tezos 2 Cross-chain bridge science At an abstract level, people can The cross-chain bridge is defined as a system that transmits information between two or more blockchains. In this case, "information" can refer to assets, contract calls, proofs, or status. Most cross-chain bridge designs have several components: Monitoring: There is usually an Actor, "Oracle", "Verifier" or "Repeater" that is responsible for monitoring the state of the chain. Message delivery/relay: After the actor receives the event, it needs to transfer the information from the source chain to the target chain. Consensus: In some models, consensus needs to be reached between participants monitoring the source chain in order to relay this information to the target chain. Signature: Actors need to cryptographically sign the information sent to the target chain either alone or as part of a threshold signature scheme. In general, there are about 4 types of cross-chain bridges: Asset-specific: Its sole purpose is to provide access to specific assets from external chains. These assets are usually "wrapped" assets, which are fully mortgaged by the underlying assets in a custody or non-custodial manner. Bitcoin is the most common asset (various xBTC) bridged to other chains, and there are seven different bridges on Ethereum alone. These cross-chain bridges are the easiest to implement and have good liquidity, but their functions are limited and need to be re-implemented on each destination chain. Chain-specific (specific to a certain chain): A cross-chain bridge between two blockchains. The main operation is to lock and unlock the tokens on the source chain, and mint and encapsulate assets on the target chain. Due to the limited complexity of these cross-chain bridges, they can usually be put on the market faster, but they are not easy to expand to a wider ecosystem. An example is Polygon’s PoS bridge, which allows users to transfer assets from Ethereum to Polygon and vice versa, but only on these two chains. Application-specific (specific to an application): An application that provides access between two or more blockchains, but only for use in that application. The application itself benefits from a smaller code base; it does not have a complete application on every blockchain, on the contrary, there are usually lighter, modular "adapters" on each blockchain. The blockchain on which the adapter is deployed can access all other blockchains connected to the application, so there is a network effect. However, the disadvantage is that it is difficult to extend this function to other applications (for example, from lending to trading). Specific examples include Compound Chain and Thorchain, which build independent blockchains dedicated to cross-chain lending and transactions. Generalized: A protocol designed to transmit information across multiple blockchains. Due to the O(1) complexity (regardless of the amount of data in the data set, the time spent is fixed), this design enjoys a strong network effect, and a single integration of a project allows it to access the entire ecosystem within the bridge system. The disadvantage is that some designs usually weigh security and decentralization to achieve this expansion effect, which may have complex and unexpected consequences for the ecosystem. An example is IBC, which is used to send messages between two heterogeneous chains (with guarantees of final confirmation).