Sui Lutris: An efficient Blockchain protocol that combines DAG Consensus and non-consensus methods

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Blockchain technology has made significant progress since the advent of Bitcoin. With the emergence of new application scenarios such as gaming and NFTs, the industry continually explores ways to enhance technical efficiency, especially in terms of handling high load and achieving real-time latency. L1 blockchains face two major challenges: first, achieving high throughput while maintaining low latency, and second, ensuring the long-term stability of consensus protocols. In addressing these challenges, it is also necessary to maintain decentralization through the dynamic participation and reconfiguration of validating nodes.

One way to achieve high throughput is to adopt DAG-based consensus protocols, such as narwhale / Bullshark. These protocols allow the blockchain to process a large number of transactions simultaneously, making them suitable for applications like games and NFTs. However, DAG-based protocols may lead to delays of a few seconds, which can be a high time cost for regular transfers or game operations.

On the other hand, consensus-free protocols like FastPay show great potential in reducing latency and scalability. These protocols do not require consensus, allowing for fast transaction processing without the need for total ordering of independent transactions in parallel processing. However, they are limited to a class of constrained simple blockchain operations, restricting the achievable smart contract functionalities, and reconfiguring the dynamically changing set of validators can be challenging.

Despite the immense potential of these methods, they have not yet been applied to production-level blockchains and have only been presented at academic conferences, without widespread adoption by the blockchain community. Sui Lutris is a protocol that supports Sui, combining DAG-based consensus and non-consensus methods to achieve the best of both worlds: sub-second latency and sustained throughput of thousands of transactions per second. Sui not only accomplishes these two tasks but also maintains the ability to express complex contracts on shared objects, generate checkpoints, and reconfigure the validator set across periods.

Sui Lutris adopts a unique approach that combines the two methods mentioned above. To ensure the security of individual asset operations by owners, the system employs a consistent broadcasting protocol among validators to achieve latency below consensus. Sui Lutris relies solely on consensus to handle complex smart contracts on shared objects. It also supports network maintenance operations, such as defining checkpoints and reconfiguring validators. This novel strategy provides a solution that balances efficiency and security when processing transactions in a replicated Byzantine environment.

The transaction lifecycle of Sui Lutris is as follows: Users create and sign the transaction, sending it to the validating nodes. The validating nodes check, sign, and return the transaction. The client collects responses from the majority of validating nodes to form a transaction certificate, at which point the transaction becomes irreversible. The certificate is sent back to the validating nodes for confirmation. Exclusive object transactions can be processed immediately, while others are forwarded to a DAG-based consensus protocol. The consensus outputs a total order of certificates, and validating nodes execute transactions that include shared objects. Clients collect responses from validating nodes to assemble the effect certificate as proof of transaction settlement. Each consensus submission forms a checkpoint for driving the reconfiguration protocol.

Sui Lutris also offers multiple features to support production-grade blockchains:

1. Implement checkpoint protocol to generate a causal history of all transactions in the system for auditing and synchronization.

2. Support reconfiguration at the end of each period, the validator set and voting rights may change.

3. Safely "unlock" erroneously locked assets at the end of the epoch to minimize vulnerability damage.

Sui Lutris supports the Sui blockchain, which manages a large amount of value. The complete technical report details how the security and liveness protocols operate, as well as the security proofs with partially synchronous Byzantine participants within the standard distributed system model.