Sui Native Bridge: The Key Infrastructure Connecting Blockchain Networks

The Sui native bridge is an important component of the Sui ecosystem, providing a reliable way for cross-chain transfers of Sui assets. In recent months, significant progress has been made in the development of the Sui native bridge, which not only enhances Sui's accessibility to a broader user base but also improves interoperability with other blockchains.

As a core element of the Sui ecosystem, the Sui native bridge facilitates the secure and efficient transfer of assets and data between Sui and other Blockchain networks. This functionality not only expands the reach of applications built on Sui but also provides a pathway for deeper integration into the broader Blockchain environment. Enhanced interoperability drives the growth and adoption of Sui, allowing assets from other networks to be migrated to the Sui platform securely and conveniently.

Overview of Sui Native Bridge

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 move assets from one chain to another and even perform more complex operations, such as cross-chain messaging.

Among the various cross-chain bridge design solutions, the Sui native bridge adopts a locking and minting mechanism, which is one of the most widely used solutions at present. As a locking and minting design, the Sui native bridge holds Ethereum native assets in Ethereum smart contracts, while on the other end of the bridging interaction, Sui assets are minted or destroyed.

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

Currently, the Sui native bridge is available on the testnet, supporting the bridging of tokens such as ETH, WETH, WBTC, and USDT between the Ethereum Sepolia and Sui testnet. After the Sui native bridge goes live on the mainnet, it will prioritize support for more assets. Future versions of the Sui native bridge plan to add new features, such as custom cross-chain messaging and integration with other Blockchains.

Technical Architecture

The Sui native bridge consists of four key components: the Sui bridge committee or node network, the Sui bridge smart contract, 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 correctly formatted transactions and collecting signatures from Sui bridge nodes. The client submits transactions on both sides of the bridge using full nodes. Sui bridge nodes also run Ethereum and Sui full nodes to listen for bridging operations and respond to these operations with the corresponding transactions. While 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 monitors the transaction and coordinates the bridging process. The Sui bridge committee operates a full Ethereum node to listen for such bridging operations to verify the legitimacy of the client requests.

After verification, bridge assets for users are minted through the Sui bridge package on Sui to complete 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 automatically execute transactions, creating a seamless bridging experience.

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

In addition, all bridge records and approvals are stored in bridge 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 Sui bridge constructs messages that are lightweight and easy for the receiving chain to decode. A universal message format is adopted to ensure that each chain can efficiently decode, verify messages, and signatures.

These bridge messages are designed to be simple and efficient, with a minimalist structure that includes only 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.

Security Design

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 some bridge designs, these attributes may be contradictory, while developing a native bridge provides an opportunity to leverage Sui's security to protect the Sui bridge.

Like the node operators who run validation nodes to ensure the security of Sui, they also manage and maintain the infrastructure that supports the operation of the Sui bridge. The Sui bridge inherits a decentralized network of node operators who are highly capable of running and protecting the Sui infrastructure.

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

The Sui bridge is protected by the same set of validating nodes that ensure the security of Sui. During the testnet phase, the committee is composed of some testnet validating nodes. After the mainnet launch, most (if not all) active Sui validating nodes will become part of the bridging committee. A dynamic management committee will be implemented after the mainnet launch 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, properties, and social consensus.

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

Signature Verification

The Sui bridge uses recoverable ECDSA signatures, allowing the public key to be recovered directly 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 authorized 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, the 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 customizable cross-chain messaging, enabling unique cross-chain interactions.

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