Sat. Jun 15th, 2024

Web3.0, the next generation Internet, has been conceived as a fully functional and user-friendly Web, and our identity and data are our own. Due to the decentralized blockchain technology, it is not subject to security protection from any centralized organization. According to this vision, Polkadot was created based on the belief that no single blockchain can do everything, more precisely, the future is multi-chain.

However, as the number and scale of blockchain networks continue to grow, they remain largely isolated from each other, just like islands with their own communities and economies, unable to exchange information or value with the outside world. The isolated nature of today's blockchain network runs counter to the principle of decentralization and reflects the existing Balkanization of the centralized Web2.0 world. (PolkaWorld Note: Balkanization is a political term that refers to the disorderly or unpredictable division of a larger region or country, or the division into smaller regions or countries. These regions or countries may be hostile or non-cooperative. )

What are bridges? Why are they so important?
A blockchain bridge is a connection that allows tokens and/or arbitrary data to be transferred from one blockchain network to another. The two chains can have different protocols, rules, communities, and governance models, but the bridge provides a compatible way to achieve secure interoperability on both sides.

There are many different designs of bridges, but they can generally be divided into two camps: centralized bridges that rely on trust or federation, and more decentralized so-called "trustless" bridges. A centralized bridge relies on a certain type of centralized organization or system to operate, which means that users need to trust an intermediary to use a given application or service.

In contrast, a trustless bridge means that users do not have to trust a single entity or authority, but instead trust the mathematical truths built in the code. Trust-free interactions are implemented by the technology and/or incentive mechanism behind the system, not through promises or legal agreements.

Polkadot is designed as an underlying infrastructure to achieve the scalability, interoperability, and security required by the multi-chain future, and to allow different Layer 1 parachains to interact and communicate with each other in the ecosystem. But Polkadot also allows parachains to interoperate with external networks such as Bitcoin or Ethereum through bridges. Currently, some bridges connecting Polkadot to external networks have been developed or are under development. Because Polkadot is designed to minimize the intermediary in the digital system, in Polkadot's ecosystem, a trustless bridge will be the first choice.

A practical example of a bridge
As a practical case of bridge chain, it is a decentralized insurance market. One way to establish this model on Polkadot is to deploy a dedicated insurance parachain to act as a market for insurance buyers and sellers. Assume that Polkadot also contains an oracle parachain that brings external data to the chain, and an Internet of Things (IoT) parachain that aggregates information from the IoT devices under the chain.

In the case that you have purchased flight delay insurance, the policy may be constructed as follows: If the oracle parachain confirms that your flight is delayed, and the IoT parachain confirms that you arrive at the airport on time, the policy will pay compensation. On the chain, if the insurance parachain receives signals from the oracle and the IoT parachain at the same time, it can use the Ethereum bridge to trigger transactions from the account of the insurance company to the account of the policy holder using stable currencies (such as Dai). This is a relatively simple example of strong interoperability.


Polkadot is designed for such a future. Not only can we see applications that are mainly deployed on one network, and occasionally do some simple transactions with other networks, but there are also some applications that actually go further and can cross different Of blockchain networks, and these networks have different degrees of specialization. A high-quality bridge brings us one step closer to this future.

Bridging the Substrate chain
The Substrate blockchain development framework can be used to build parallel chains (when combined with Cumulus consensus engine) and separate chains with their own consensus and security. Parachains connected and protected by Polkadot or Kusama relay chains are first-class citizens of the ecosystem. Substrate-based single chains can also be connected through bridges and communicate with the parachains of the ecosystem.

The Parity team is currently developing a universal bridge that can connect to Substrate-based chains. This bridge is composed of multiple components that together support two-way communication between an independent Substrate-based chain and the Polkadot parachain, or support two-way communication between two independent Substrate-based chains. In particular, this bridge will also enable Polkadot and Kusama to interact. You can view the progress of the Parity Trustless Bridge in the Parity Bridges repository.

Bridge supported by Web3 Foundation Grant
The grant program of the Web3 Foundation has supported the development of many bridges in the Polkadot ecosystem, including the following:

Interlay is building a trustless bridge from Bitcoin to Polkadot. Currently in the beta testing phase, it will allow users to cast Bitcoin-backed assets into PolkaBTC on Polkadot at a ratio of 1:1. PolkaBTC can be used in any application or parachain in the Polkadot ecosystem, just like a local asset, thereby releasing BTC liquidity for Polkadot's DeFi. Internally, PolkaBTC implements the XCLAIM protocol, which makes the bridge financially trustless, license-free, and anti-censorship. PolkaBTC's rewarding Beta test network has been launched at the end of February and has greatly improved the user experience. At the same time, PolkaBTC is being audited by NCC, and Interlay has begun to integrate PolkaBTC with Rococo's other parachains.

Snowfork is building a universal bridge chain between Ethereum and Polkadot. This can not only transfer ETH from Ethereum to Polkadot, but also transfer ERC20 assets and arbitrary data. In addition to asset transfer, this bridge chain can also be used for more complex interactions, such as cross-chain smart contract calls. For example, any application built on Polkadot can use a bridge to send Dai directly from one account to another account on the Ethereum blockchain.

Darwinia is building a permissionless non-custodial bridge chain protocol that has the functions of cross-chain token and NFT transfer and other cross-chain operations for efficient, low-cost decentralization. Darwinia Bridge integrates technologies such as ultra-light client, zero-knowledge, and optimistic verification mechanisms. Darwinia has launched a bridge with Ethereum and plans to implement more bridges connecting major heterogeneous blockchains in the future, such as BSC, Tron, Filecoin, etc.

Centrifuge cooperated with ChainSafe to develop a modular, agnostic asset, multi-directional bridge chain based on the Substrate blockchain and Ethereum. ChainBridge allows Centrifuge to move replaceable and NFT assets between chains, thereby financing real assets in various DeFi products. ChainBridge is open source, and it also allows other teams in the ecosystem to build bridges with their projects.

ChainX, an encrypted asset gateway, is planning to bridge multiple networks and has implemented a BTC to Substrate bridge. In this design, the bridge is run by validators who bet on ChainX's PoS consensus and control the BTC multi-signature wallet.

Bifrost has developed an EOS network bridge that uses merkle tree verification to implement light nodes on the chain, thereby realizing trustless cross-chain asset transfer. The third version of their testnet, Bifrost Asgard CC3, has recently been released. In the future, Bitfrost plans to work on interoperability with EOS contracts.

Bridging the future of Web3.0
The future of blockchain Internet infrastructure lies in everyone working together in a spirit of cooperation. We are committed to connecting the community to the Substrate and Polkadot ecosystems, and we are committed to providing reusable development components that make it easy to build and deploy bridge chains that connect to other blockchains. learn more :

Learn more about the Polkadot bridge in our Wiki
View the collection of components that build the bridge chain on GitHub
Discuss bridge chains with others on Element
Learn more about Polkadot on our official website
Use your favorite medium to join the Polkadot conversation

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