基于PBFT共识算法的区块链改进方案

Blockchain Improvement Scheme Based on PBFT Consensus Algorithm

摘要: 针对应用于联盟链的实用拜占庭容错(PBFT)共识算法存在的主节点取余方法容易导致恶意节点当选、三阶段共识流程导致高时延等问题，提出了一种改进的实用拜占庭容错(PBFT+)共识算法。首先，基于信用机制来选取主节点，引入信用层次体系对系统节点进行信用评价，共识节点的信用层次随着其产生有效区块的数量进行动态变化，节点的信用层次划分是系统对节点的评判标准，系统将选取全网信用值最高的节点作为主节点，可以保证主节点的最优性。通过备用主节点机制避免频繁发生视图变更，提高系统可用性和安全性。其次，优化PBFT共识算法的三阶段共识流程，将确认阶段中全网节点广播确认消息改进为由主节点收集确认消息，减少了通信开销。实验部分将PBFT+算法与PBFT算法进行多组对比测试，通过仿真实验结果表明，PBFT+算法有效的减少了系统资源的消耗，降低了时延。

Abstract: Aiming at the problems of the master node surplus method of the Practical Byzantine Fault Tolerance Consensus algorithm applied to the alliance blockchain, which may easily lead to the election of malicious nodes and the high latency caused by the three-stage consensus process. In this paper, we extend PBFT with credit mechanism, denoted as PBFT+. More specifically, we introduce a credit mechanism to select the primary node instead of random selection, leading into a credit hierarchy system for credit evaluation of system nodes. The credit level of consensus node changes dynamically with the number of valid blocks that it generates. The credit level division of nodes is the system criterion for judging nodes, and the system will select the node with the highest credit value of the whole network as the master node to ensure the optimality of the master node. The availability and security of the system can be improved by using the standby primary node mechanism to avoid frequent view changes. Furthermore, the three-stage consensus process of the PBFT algorithm is optimized. In the confirmation phase, the primary node collects the confirmation information instead of broadcasting the message from the entire network node, which reduces the communication overhead. In the experimental part, the PBFT+ and the PBFT algorithm are tested in multiple groups. The experimental simulation results show that the PBFT+ algorithm can effectively reduce the consumption of system resources and reduce the delay.