Translation: Sui World
Since the birth of Bitcoin a decade ago, blockchain technology has made great strides. With the emergence of new use cases such as gaming and NFTs, the blockchain community is constantly exploring ways to improve technical efficiency, especially in handling high loads and providing real-time latency. L1 blockchains face two major challenges: the need to achieve high throughput while maintaining low latency, and ensuring long-term stability of the consensus protocol. While addressing these challenges, decentralization should be maintained through dynamic participation of validating nodes and reconfiguration of validating nodes.
One way to achieve high throughput is to use DAG-based consensus protocols such as narwhale/Bullshark used by Sui. These consensus protocols enable blockchains to process large numbers of transactions simultaneously, making them an ideal choice for use cases such as gaming and NFTs. However, DAG-based protocols can result in delays of several seconds, which can be costly in terms of time for regular transfers or gaming operations.
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On the other hand, consensus-free protocols such as FastBlockingy show great promise in reducing latency and scaling. These protocols eliminate the need for consensus, allowing for fast processing of transactions without total ordering of independently processed transactions in parallel. However, they are limited to a class of restricted simple blockchain operations, which limits the smart contracts they can perform, and reconfiguring dynamically changing sets of validators may be challenging.
Although they have potential, these methods are not currently used in production-level blockchains, and they are currently only published at academic conferences and not widely used by the blockchain community. Sui Lutris is a protocol that supports Sui, which combines DAG-based consensus and consensus-free methods to achieve the best of both worlds: sub-second latency and sustained throughput of thousands of transactions per second. Sui accomplishes both tasks and maintains the ability to express complex contracts on shared objects, generate checkpoints, and reconfigure validator sets across epochs.
Combining Consensus-Based and Non-Consensus-Based Methods
Sui Lutris takes a unique approach by combining the above two methods. To ensure the safety of operations on assets owned by a single owner (owned objects), the system adopts a consistent broadcasting protocol between validators, resulting in lower latency than consensus. Sui Lutris relies only on consensus to handle complex smart contracts running on shared objects, i.e., objects that any user can change. Sui Lutris also supports network maintenance operations such as defining checkpoints and reconfiguring validators. This novel strategy provides a best-of-both-worlds approach when processing transactions in a replicated Byzantine environment.
Advanced description and transaction lifecycle in Sui Lutris.
Users with private keys create and sign user transactions to change either objects they own or a mix of objects they own and shared objects. The transaction is sent to each Sui Lutris validation node (typically via full nodes), which performs a series of validity and security checks, signs it, and returns the signed transaction to the client. The client collects responses from the majority of validation nodes to form a transaction certificate, at which point the transaction can be considered irreversible (reaching finality).
Once the certificate is assembled, it is sent back to all validation nodes, which check its validity and confirm receipt to the client. If the transaction involves exclusive objects, the transaction certificate can be processed and executed immediately, without waiting for the consensus engine (direct fast path). All certificates are forwarded to our DAG-based consensus protocol (also operated by Sui validation nodes). Consensus ultimately outputs a total order of certificates; validation nodes check and execute those transactions that involve shared objects, and clients can collect responses from the majority of validation nodes, assemble them into an effect certificate, and use it as proof of transaction settlement. Subsequently, a checkpoint is formed for each consensus submission, which is also used to drive protocol reconfiguration.
In addition to the primary transaction flow shown in the figure above, Sui Lutris provides many facilities to support production-grade blockchain:
1) Implement a checkpoint protocol after achieving final determinism, which produces the causal history of all transactions in the system. This is used for complete auditing, as well as to keep full nodes and lagging validation nodes synchronized in an efficient way.
2) Sui Lutris supports reconfiguration at the end of each epoch, when the set of validators and their voting power may change, to ensure that all final transactions are included in one epoch, each epoch needs careful closure and confirmation that it is final and secure.
3) In previous consensus-free protocols, when a buggy client double-spent assets, the assets would be locked forever. Sui Lutris safely “unlocks” erroneously locked assets at the end of the epoch, minimizing the damage caused by the bug.
Sui Lutris supports Sui, a blockchain for managing large amounts of value for users. The full technical report provides more detailed information on how the security and liveness protocols work and their security proofs against partially synchronous Byzantine participants in the standard distributed systems model.
Regarding Sui Lutris, you can click the following link to access the complete technical report: