Over recent months, significant efforts have been dedicated to developing Sui Bridge, a native bridge for the Sui ecosystem. This initiative enhances the accessibility of Sui for the broader community and improves interoperability with other blockchains.

Sui Bridge Background

In the blockchain ecosystem, a bridge is a protocol that enables interaction and communication between independent blockchain networks. Bridges facilitate the transfer of data across boundaries, allowing users to move their assets from one chain to another and even perform more complex operations like cross-chain message passing.

Sui Bridge utilizes a lock and mint mechanism, holding Ethereum-native assets within Ethereum smart contracts while minting or burning Sui assets depending on the direction of the bridge interaction. As a native bridge on Sui, it requires no additional trust. The same entities that secure Sui also secure Sui Bridge, and its code is integrated into the Sui framework.

Currently available on Testnet, Sui Bridge supports tokens such as ETH, WETH, WBTC, and USDT between Ethereum Sepolia and Sui Testnet. Following its Mainnet release, support for more assets will be prioritized, and future versions will introduce new functionalities like custom cross-chain messaging and integration with other blockchains.

High Level Architecture

Sui Bridge comprises four key components: the Sui Bridge committee or node network, the Sui Bridge smart contracts, the full nodes operating on Ethereum and Sui, and the bridge client.

The client acts as the interface between the user and the Sui Bridge infrastructure, coordinating user bridging actions by submitting correctly formatted transactions and collecting Sui Bridge node signatures as needed. Full nodes on both sides of the bridge submit transactions, while bridge nodes also run Ethereum and Sui full nodes to listen for and respond to bridging actions.

When bridging assets from Ethereum to Sui, the user deposits assets into the Sui Bridge smart contract on Ethereum. The client observes this transaction and coordinates the process. The Sui Bridge committee, operating Ethereum full nodes, verifies the legitimacy of the client’s request. After verification, the bridging action is completed by minting bridged assets for the user through the Sui Bridge package on Sui. Currently, Sui Validators subsidize the gas fees associated with bridging transactions.

When bridging from Sui to Ethereum, the process is similar, except users must manually submit the claiming transaction on Ethereum. This transaction includes signature data from the Sui Bridge nodes, allowing the Ethereum account to redeem the specified assets locked in the bridge contract.

All bridging records and approvals are stored in the bridge object on-chain, with governance actions controlled by the Sui Bridge committee.

Bridge Messages

Sui Bridge constructs messages in a lightweight manner to ensure low gas costs. A common messaging format is employed to ensure each chain can efficiently decode and verify messages and signatures. The structure is minimalistic, containing only essential fields such as message type, version, sequence number, source chain identifier, and payload.

Bridge Security

Determining a bridge’s trust model is crucial for supporting a bustling ecosystem and large flows. Sui Bridge leverages the security of Sui to ensure both security and decentralization. The same node operators that secure Sui also manage and maintain the Sui Bridge infrastructure.

Sui Bridge utilizes recoverable ECDSA signatures, allowing public key recovery directly from the signature itself. This streamlines the verification process, ensuring only legitimate transactions are processed. A message is considered valid only when the combined weight of the signatures meets or exceeds a predefined threshold.

Building Interoperability

The Sui native bridge provides a secure and efficient means of transferring assets between blockchain networks, laying the groundwork for more advanced cross-chain interactions. By leveraging its robust trust model, incorporating ECDSA for secure transactions, and employing a committee-based signature verification process, Sui Bridge ensures high security and reliability.

As the ecosystem develops, the bridge will support a wider array of assets and abilities, such as custom cross-chain messaging. Sui Bridge represents a significant step forward in the landscape of Sui interoperability, offering a seamless and highly secure solution for cross-chain asset transfers.

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