Sui Ecosystem Native Cross-Chain Bridge Achieves Significant Progress

Recently, the native cross-chain bridge of the Sui ecosystem, Sui Bridge, has made significant progress in development. This initiative not only enhances Sui's accessibility to a broader community but also improves interoperability with other blockchains.

As a key component of the Sui ecosystem, Sui Bridge facilitates the secure and efficient transfer of assets and data between Sui and other blockchain networks. This functionality not only broadens the impact of applications built on Sui but also provides a pathway for deeper integration into the wider blockchain environment. The increase in interoperability contributes to the growth and adoption of Sui, allowing assets from other networks to be securely and conveniently migrated to the Sui platform.

Sui Bridge Background

In the blockchain ecosystem, cross-chain bridges are protocols that allow interaction and communication between independent blockchain networks. Cross-chain bridges facilitate the transfer of cross-chain data, enabling users to transfer assets from one chain to another, and even perform more complex operations such as cross-chain messaging.

Among the many cross-chain bridge design options, Sui Bridge uses a locking and minting mechanism, which is one of the most widely used solutions. As a locking and minting design, Sui Bridge holds Ethereum native assets in Ethereum smart contracts, and in the direction of bridging interactions, Sui assets are either minted or burned.

As the native bridge of Sui, Sui Bridge does not require additional trust. Sui Bridge is secured by the nodes of the Sui network, and its code is embedded in the Sui framework.

Currently, Sui Bridge is available on the testnet, supporting the bridging of tokens such as ETH, WETH, WBTC, and USDT between the Ethereum Sepolia and Sui testnets. After the mainnet launch of Sui Bridge, it will prioritize supporting more assets. Future versions of Sui Bridge will add new features such as customizable cross-chain messaging and integration with other blockchains.

Advanced Architecture

Sui Bridge consists of four key components: the Sui Bridge committee or node network, the Sui Bridge smart contract, the full nodes running on Ethereum and Sui, and the bridging client.

The client is the interface between the user and the Sui Bridge infrastructure. It coordinates the user's bridging operations by submitting properly formatted transactions and collecting signatures from Sui Bridge nodes. The client uses full nodes to submit transactions on both sides of the bridge. Sui Bridge nodes also run Ethereum and Sui full nodes to listen for bridging operations and respond to these operations through subsequent transactions. Although the bridging client is permissionless and can be executed by anyone, many bridging nodes will activate the bridging client to ensure the network's activity.

When bridging from Ethereum to Sui, users deposit assets into the Sui Bridge smart contract on Ethereum. The client then observes the transaction and coordinates the bridging process. The Sui Bridge committee operates an Ethereum full node, listening for such bridging operations to verify the legitimacy of client requests.

After verification, bridge assets are minted for users through the Sui Bridge package on Sui, completing the bridging operation. Due to the low bridging costs, Sui validator nodes currently subsidize the gas fees related to bridging transactions on Sui, allowing clients to execute transactions automatically and creating a seamless bridging experience.

The process of bridging from Sui to Ethereum is similar, except that users must manually submit a claim transaction on Ethereum. This transaction includes the signature data from the Sui Bridge node, allowing the Ethereum account to redeem the specified assets locked in the bridging contract.

In addition, all bridging records and approvals are stored in the bridging objects on the chain. This is feasible on Sui because its storage and gas fees are relatively low. The Sui Bridge contract also handles governance operations, which are controlled by the Sui Bridge committee.

Bridging Message

To ensure low gas fees, the messages constructed by Sui Bridge are lightweight and easy to receive chain decoding. A universal message format is adopted to ensure that each chain can efficiently decode, verify messages, and signatures.

These bridging messages are designed to be simple and efficient, with a minimal structure that only includes basic fields such as message type, version, sequence number, source chain identifier, and payload. This simplified design reduces complexity and computational overhead, ensuring low gas fees while facilitating fast and reliable cross-chain communication.

Bridge Security

Determining the trust model of the bridge is one of the most important design decisions when developing cross-chain bridges to support a thriving ecosystem and large-scale liquidity. Cross-chain bridges should be both secure and decentralized, and in certain bridge designs, these attributes may conflict with each other. Developing a native bridge provides the opportunity to leverage Sui's security to protect the Sui Bridge.

Like the operators of the verification nodes that ensure the security of Sui, they also manage and maintain the infrastructure that runs the Sui Bridge. The Sui Bridge inherits a decentralized network of node operators, who are highly capable of running and safeguarding the Sui infrastructure.

As mentioned above, most Sui Bridge operations are conducted on Sui, treating Sui as the control panel of the bridge. This is due to the security inherited from the software developed in Move.

Bridge Committee

Sui Bridge is protected by the same set of validating nodes that ensure Sui's security. During the testnet phase, the committee consists of some testnet validating nodes. After the mainnet goes live, most (if not all) active Sui validating nodes will become part of the bridging committee. After the mainnet launch, a dynamic management committee will be implemented to allow new validating nodes to join. Only Sui validating nodes are allowed to become part of the Sui Bridge committee, ensuring the inheritance of its security assumptions, attributes, and social consensus.

To maintain high security and compatibility with other blockchain networks, Sui Bridge uses the Elliptic Curve Digital Signature Algorithm (ECDSA) for committee signatures. By leveraging ECDSA, Sui Bridge ensures seamless interoperability and secure transaction validation, strengthening the integrity and trustworthiness of the system.

Signature Verification

Sui Bridge uses recoverable ECDSA signatures, allowing the public key to be directly recovered from the signature. This feature simplifies the verification process, enabling us to retrieve the public key and confirm the authenticity and integrity of the signature without prior knowledge of the public key.

A message is only considered valid when the total weight of the signatures reaches or exceeds a predetermined threshold. This threshold mechanism ensures that a sufficient number of authenticating signatures are required to verify the message, thereby enhancing the security and reliability of the system. By implementing this approach, we can prevent fraudulent activities and ensure that only legitimate transactions are processed.

Building Interoperability

The Sui native bridge not only provides a secure and efficient means of transferring assets between blockchain networks but also lays the foundation for more advanced cross-chain interactions. By leveraging its robust trust model, integrating ECDSA for secure and verifiable transactions, and employing a committee-based signature verification process, Sui Bridge ensures high security and reliability while maintaining flexibility.

The scalability and flexibility of the Sui bridge architecture allow for future expansions and integration with other blockchain networks. As the ecosystem develops, the bridge will support a wider range of assets and functionalities, such as customized cross-chain messaging, enabling unique cross-chain interactions.

Sui Bridge represents a significant advancement in the field of Sui interoperability, providing a seamless and highly secure cross-chain asset transfer solution. With the launch of Sui Bridge on the mainnet, users can expect an increasingly robust and versatile cross-chain bridge that meets current demands while also anticipating future needs.