- Polkadot’s ecosystem will be inter-connectable with other blockchains using Substrate-based chains as bridges.
- Parachains use queuing mechanisms for inter-chain communication called XCMP and HRMP.
- Parity builds a generic bridge to enable all kind of connections to Polkadot’s ecosystem.
To build a “decentralized future”, the Polkadot team has introduced “Bridges” that will allow it to connect its ecosystem with external blockchains. Polkadot’s infrastructure and features have been created to provide such interoperability and enable use cases that go beyond traditional conception.
The Polkadot team envisions a future where an application can go “further” and cohabit within many blockchains with “varying degrees of specialization.” Thus, Polkadot’s infrastructure envisions a design for its “bridges” based on Substrate’s blockchain framework.
The bridge design for the Polkadot ecosystem
These bridges allow developers to build blockchains alongside the Cumulus consensus engine. In addition, it enables blockchain construction with its own consensus and security protocol.
Therefore, the parachains within Polkadot communicate with a queuing mechanism called Cross-Chain Message Passing (XCMP) and Horizontal Relay Message Passing (HRMP). According to the Polkadot team:
Substrate also enables developers to build standalone chains, allowing them to choose their own consensus mechanism and remain independent from Polkadot. It’s still possible for these chains to connect and communicate to the ecosystem using bridges.
Parity Technologies team is currently building a “generic bridge” that will allow connecting Substrate-based chains. The connected networks will have bidirectional communication between a Polkadot parachain and a Substrate-based chain.
In principle, the bridge developed by Parity will enable interoperability between Kusama Networks and Polkadot. However, there are other bridges in development with many more connection possibilities not limited to Substrate-based chains.
Teams building bridges on Polkadot
Many of the teams working on such bridges have been supported by the Web3 Foundation. Among them is Interlay, which is building a Bitcoin bridge to Polkadot and is in beta testing. Users will be to mint 1:1 Bitcoin-backed assets onto Polkadot as PolkaBTC. PolkaBTC can then be used with any parachain just like a native asset, unlocking BTC liquidity for Polkadot’s DeFi.
Snowfork’s team builds a “general purpose” bridge between Ethereum and Polkadot. That way, its users will be able to make transfers with ETH and other tokens based on the ERC-20 standard and even build cross-chain smart contracts.
Darwinia is creating a “permissionless non-custodial bridge protocol “that will enable low-cost transfers for non-fungible tokens and cross-chain tokens. Also, the Darwinia bridge includes super light clients, zero knowledge, and optimistic verification mechanisms. The bridge has been launched on Ethereum and hopes to connect to other blockchains such as Tron, Binance Smart Chain, Filecoin and others.
Finally, ChainX and Bifrost teams developed bridges that will leverage the capabilities of Bitcoin and the EOS network respectively. ChainX is operated by validators, staked in ChainX’s Proof of Stake consensus, controlling a BTC multi-sig wallet. Bifrost will deploy a bridge to EOS that trustless cross-chain asset transfers.