Abstract: In order to solve the problems of high communication complexity and low consensus efficiency of practical Byzantine fault-tolerant (PBFT) consensus mechanism in the consortium chain under the condition of increasing number of nodes in the blockchain network, a multi-primary-node Byzantine fault-tolerant consensus mechanism based on Raft IMRBFT is proposed. Firstly, the Maglev consensus hash algorithm is used to evenly group the nodes of the blockchain network, and the consensus process is divided into two parts: out-of-group consensus and intra-group consensus. The leader node is first selected in the group, and the node is divided into three levels through the credit mechanism: trusted node, ordinary node and untrusted node. Together with the voting mechanism, it reduces the probability of malicious nodes becoming leader nodes, and forms a committee with other group leader nodes, and the committee selects multiple primary nodes with the highest credit value through the external credit value mechanism to conduct PBFT consensus outside the group. On the basis of Raft consensus, intra-group consensus introduces supervision nodes and relay nodes to further improve security and consensus efficiency and reduce the evil behavior of malicious nodes. Finally, the experimental results show that the communication overhead of IMRBFT increases linearly, the traffic volume is 41.6% of PBFT, the throughput is 4.2 times that of PBFT, and the consensus delay is reduced by 76.4%. With the increase of nodes, the optimization is more obvious, which fully meets the requirements of small communication complexity, high throughput, short consensus delay, and high security and consensus efficiency of large-scale blockchain networks.

Key words: blockchain, consensus mechanism, node grouping, credit mechanisms, Byzantine tolerance, Raft algorithm