A promising way to overcome the scalability limitations of the current blockchain is to use sharding, which is to split the transaction processing among multiple, smaller groups of nodes. A well-performed blockchain sharding system requires both high performance and high security in both intra- and cross-shard perspectives. However, existing protocols either have issues on protecting security or trade off great performance for security. In this paper, we propose SP-Chain, a blockchain sharding system with enhanced Security and Performance for both intra- and cross-shard perspectives. For intra-shard aspect, we design a two-phase concurrent voting scheme to provide high system throughput and low transaction confirmation latency. Moreover, we propose an efficient unbiased leader rotation scheme to ensure high performance under malicious behavior. For cross-shard aspect, a proof-assisted efficient cross-shard transaction processing mechanism is proposed to guard the cross-shard transactions with low overhead. We implement SP-Chain based on Harmony, and evaluate its performance via large-scale deployment. Extensive evaluations suggest that SP-Chain can process more than 10,000 tx/sec under malicious behaviors with a confirmation latency of 7.6s in a network of 4,000 nodes.

翻译：为克服现有区块链的可扩展性限制，分片技术成为一种极具前景的解决方案，其核心在于将交易处理任务分配给多个规模较小的节点组。一个性能优异的区块链分片系统需要在分片内与跨分片两个维度上同时具备高性能与高安全性。然而，现有协议要么在安全保障方面存在不足，要么为追求安全性而大幅牺牲了性能。本文提出SP-Chain，一种在分片内与跨分片维度均具备增强安全性与性能的区块链分片系统。在分片内层面，我们设计了一种两阶段并行投票方案，以提供高系统吞吐量与低交易确认延迟。此外，我们提出了一种高效无偏的领导者轮换方案，确保在恶意行为存在时仍能维持高性能。在跨分片层面，我们提出了一种基于证明的高效跨片交易处理机制，以较低开销保障跨片交易安全。我们在Harmony基础上实现了SP-Chain，并通过大规模部署评估其性能。大量实验结果表明，在一个包含4000个节点的网络中，SP-Chain在存在恶意行为的情况下仍能处理超过10,000笔交易/秒，且确认延迟仅为7.6秒。