In-depth Understanding of Sui Native Cross-Chain Bridge Technology Architecture

The Sui native bridge provides a trust-minimized way for cross-chain transfers of Sui assets. In recent months, significant progress has been made in the development of this bridge, which 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, the Sui native 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 a broader blockchain environment. The increase in interoperability promotes the growth and adoption of Sui, allowing assets from other networks to migrate to Sui safely and easily.

Background 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, allowing users to transfer assets from one chain to another and even perform more complex operations such as cross-chain messaging.

Among the various cross-chain bridge design options, the Sui native bridge adopts a locking and minting mechanism, which is one of the most widely used solutions. As a locking and minting design, this bridge holds Ethereum native assets in Ethereum smart contracts, while in the direction of bridging interactions, Sui assets will be minted or burned.

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

Currently, the 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, more assets will be prioritized for support. Future versions will add new features such as custom cross-chain messaging and integration with other blockchains.

Advanced Architecture

The Sui native bridge has four key components: the bridge committee or node network, the bridge smart contract, the full nodes running on Ethereum and Sui, and the bridge client.

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

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

After verification, the bridge package on Sui mints bridging assets for users, thereby completing the bridging operation. Due to the low bridging costs, Sui validation nodes currently subsidize the gas fees related to bridging transactions on Sui, allowing clients to execute transactions automatically, creating a seamless bridging experience.

When bridging from Sui to Ethereum, the process is similar, but users must manually submit a claim transaction on Ethereum. This transaction includes the signature data from the 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 due to its relatively low storage and gas fees. The bridge contract also handles governance operations, which are controlled by the bridge committee.

Bridging Message

To ensure low gas fees, the Sui native bridge constructs messages that are lightweight and easy for receiving chains to decode. A universal message format is used 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 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 a 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 be in conflict, while developing native bridges provides the opportunity to leverage Sui's security to protect the Sui native bridge.

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

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

Bridge Committee

The Sui native bridge is protected by the same set of validating nodes that ensure the security of Sui. During the testnet phase, the committee consists of a portion of 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 goes live, allowing new validating nodes to join. Only Sui validating nodes are allowed to become part of the Sui native bridge committee, ensuring the inheritance of its security assumptions, attributes, and social consensus.

To maintain high security and compatibility with other blockchain networks, the Sui native bridge uses the Elliptic Curve Digital Signature Algorithm (ECDSA) for committee signatures. By utilizing ECDSA, the bridge ensures seamless interoperability and secure transaction verification, reinforcing the system's integrity and credibility.

signature verification

The Sui native 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 authenticated signatures are required to verify the message, thereby enhancing the security and reliability of the system. By implementing this approach, fraudulent activities can be prevented, ensuring 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 bridge ensures high security and reliability while maintaining flexibility.

The scalability and flexibility of the Sui native bridge architecture allows 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 custom cross-chain messaging, enabling unique cross-chain interactions.

This bridge represents a significant advancement in the field of interoperability for Sui, providing 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 multifunctional cross-chain bridge that meets current needs while also anticipating future demands.