基于实用拜占庭容错的改进的多主节点共识机制

针对实用拜占庭容错（PBFT）共识协议通信复杂度高导致的共识效率低、单一主节点发生故障或存在拜占庭行为时会导致共识过程停止的问题，提出了改进的多主节点实用拜占庭容错（IMPBFT）共识机制。首先，通过节点的共识轮数、存在拜占庭行为的共识轮数以及节点被赋予的优先值，计算出节点的有效共识轮数，再依据有效共识轮数的大小选出多个主节点。其次，对原共识机制进行改进，使所有节点利用改进的机制进行共识。最后，引入流水线来实现IMPBFT共识的并发执行。在进行流水线操作时，不同轮共识的多阶段消息统一签名，并且不再使用固定周期来控制流水线。理论研究和实验结果表明，IMPBFT的多主节点结构相较单一主节点的共识结构更加安全稳定；与平方级通信量的PBFT和信用委托拜占庭容错（CDBFT）共识相比，IMPBFT将通信量降至线性级；在交易吞吐量、扩展性和交易时延方面，IMPBFT的性能要优于PBFT和CDBFT；使用“多阶段消息统一签名、无固定周期”流水线的IMPBFT，比未使用流水线的IMPBFT在交易吞吐量上提高了75.2%。

Improved multi-primary-node consensus mechanism based on practical Byzantine fault tolerance

The high communication complexity of Practical Byzantine Fault Tolerance （PBFT） consensus protocol will lead to low consensus efficiency， the failure or the existing of Byzantine behavior of the single primary node will lead to the stop of consensus process. In order to solve these problems， an Improved Multi-primary-node Practical Byzantine Fault Tolerance （IMPBFT） consensus mechanism was proposed. Firstly， the number of effective consensus rounds of nodes was calculated by the number of consensus rounds of nodes， the number of consensus rounds with Byzantine behavior and the priority values assigned to the nodes， and several primary nodes were selected according to the size of effective consensus rounds. Then， the original consensus mechanism was improved to make all nodes use the improved consensus mechanism for consensus. Finally， pipeline was introduced to implement the concurrent execution of IMPBFT consensus. In the pipeline operation， multi-stage messages of different rounds’ consensus were signed together， and no fixed cycle was used to control the pipeline. Theoretical research and experimental results show that， the multi-primary-node structure of IMPBFT is more secure and stable than the consensus structure of single primary node. Compared with PBFT and Credit-Delegated Byzantine Fault Tolerance （CDBFT） consensus with square level traffic， the proposed IMPBFT reduces the traffic to linear level. The IMPBFT has better performance than PBFT and CDBFT in terms of transaction throughput， scalability and transaction delay. The IMPBFT using the “multi-stage messages signed together with no fixed cycle” pipeline has improved the transaction throughput by 75.2% compared with the IMPBFT without pipeline.