Abstract:

Sharding technology is a feasible scheme to solve the problem of blockchain expansion, but there is a contradiction between the scale of the sharding and the verification validity in shards：with PBFT consensus algorithm, even if the proportion of Byzantine nodes is no more than one third in all nodes, there is a certain probability that the proportion of Byzantine nodes will exceed one third in a single sharding, resulting in the failure of verifying the consensus. Aiming at this problem, it proposes an improved scheme of multi-round PBFT consensus, which can not only improve the scale of the sharding, but also ensure the verification validity of the PBFT consensus in the sharding. Firstly, it summarizes the schemes of the known projects and analyzes their advantages and disadvantages. Then it analyzes consensus verification validity of sharding in detail. Lastly, it proposes and discusses the multi-round verification scheme, giving reasonable value of multiple rounds in the case of high Byzantine nodes proportion. Based on the comparison between the experimental data and the existing scheme, it verifies the validity of the multi-round scheme in improving the overall TPS, which provides a useful reference for the further study of the sharding scheme.

Key words: low Transaction Per Second（TPS）, sharding, consensus mechanism, Practical Byzantine Fault Tolerance（PBFT）, multi-round verification

摘要：

分片技术是解决区块链扩容难题的可行方案，但存在分片规模与分片内验证有效性的矛盾：采用PBFT共识算法，即使总体拜占庭节点数占比不超过三分之一，单个分片内拜占庭节点占比也存在一定概率会超过三分之一，无法验证共识。针对该问题，提出多轮PBFT共识的改进方案，在提高分片规模的同时，保证分片内PBFT共识的验证有效性。总结了已知项目的解决方案并分析优缺点，详细分析了分片的有效共识验证，提出并论述了多轮验证方案，给出了拜占庭比例节点较高情况下多轮轮数的合理取值。基于实验得到的数据与现有方案进行对比，验证了多轮方案在提升整体TPS方面的有效性，为分片方案的进一步研究提供有益的参考。

关键词: 低TPS, 分片, 共识机制, 实用拜占庭容错算法（PBFT）, 多轮验证