Sharding enhances blockchain scalability by dividing the network into shards, each managing specific unspent transaction outputs or accounts. Cross-shard transactions pose a critical challenge to the security and efficiency of sharding blockchains. Current solutions, however, either prioritize security with assumptions and substantial investments, or focus on reducing overhead and overlooking security considerations. In this paper, we present Kronos, a generic and efficient sharding blockchain consensus ensuring robust security. We introduce a buffer mechanism for atomic cross-shard transaction processing. Shard members collectively maintain a buffer to manage cross-shard inputs, ensuring that a transaction is committed only if all inputs are available, and no fund is transferred for invalid requests. While ensuring security, Kronos processes transactions with optimal intra-shard communication overhead. Additionally, we propose a reduction for transaction invalidity proof generation to simple and fast multicasting, leading to atomic rejection without executing full-fledged Byzantine fault tolerance protocol in optimistic scenarios. Moreover, Kronos adopts a newly designed batch mechanism, reducing inter-shard message complexity to $O((m$log$m/b)\lambda)$. Kronos operates without dependence on any time or client honesty assumption, serving as a plug-in sharding blockchain consensus supporting applications in diverse network environments including asynchronous ones. We implement Kronos using two prominent BFT protocols: Speeding Dumbo and HotStuff. Extensive experiments demonstrate Kronos achieving a substantial throughput of 68.6ktx/sec with 1.7sec latency. Compared with state-of-the-art solutions, Kronos outperforms in all cases, achieving up to a 42x improvement in throughput and a 50% reduction in latency when cross-shard transactions dominate the workload.

翻译：分片技术通过将网络划分为多个分片，每个分片管理特定未花费交易输出或账户，从而提升区块链可扩展性。跨分片交易对分片区块链的安全性与效率构成关键挑战。然而，现有解决方案要么通过假设和大量投入优先保障安全，要么专注于降低开销而忽视安全考虑。本文提出Kronos，一种通用且高效的分片区块链共识，确保鲁棒安全性。我们引入一种缓冲区机制用于原子性跨分片交易处理。分片成员共同维护一个缓冲区来管理跨分片输入，确保交易仅在所有输入可用时提交，且不会因无效请求转移资金。在保证安全性的同时，Kronos以最优的分片内通信开销处理交易。此外，我们提出将交易无效性证明生成简化为简单快速的组播，从而在乐观场景下无需执行完整的拜占庭容错协议即可实现原子拒绝。进一步地，Kronos采用新设计的批处理机制，将分片间消息复杂度降至$O((m$log$m/b)\lambda)$。Kronos的运行不依赖任何时间或客户端诚实的假设，可作为即插即用的分片区块链共识，适用于包括异步网络在内的多样化网络环境。我们使用两种主流拜占庭容错协议——Speeding Dumbo和HotStuff——实现了Kronos。大量实验表明，Kronos在1.7秒延迟下可实现高达68.6千交易/秒的吞吐量。与最先进解决方案相比，Kronos在所有场景下均表现更优，在跨分片交易占主导时，吞吐量提升最高达42倍，延迟降低50%。