Abstract: Proof of stake consensus algorithm(PoS) has the advantage of not requiring arithmetic power.However,the higher the equity of the node,the higher the probability of obtaining the bookkeeping rights,resulting in a very deterministic bookkeeping node and makes it easy for the rich to get richer.Once the node with the highest equity fails to book the block properly,the rest of the nodes still have to compete for the bookkeeping rights again.The probability of system stagnation increases dramatically at this point.To address these two shortcomings,a consensus optimization algorithm for proof of importance based on dynamic grouping(DPoI) is proposed.The algorithm introduces an importance assessment scheme,which calculates the importance score iValue of nodes in each round based on node activity,transaction share,time to find random numbers and reputation.Then,the nodes with similar iValue are dynamically grouped using Fibonacci series.Within the group,the DPoS voting strategy ranking is borrowed to act as an alternative node,thus forming a disaster recovery scheme to effectively avoid system stagnation.Finally,a binary exponential backoff algorithm is designed to quickly remove malicious nodes from the system,thus effectively enhancing the security and stability of the blockchain system.Experimental results show that the speed of DPoI block-out is about 6 times faster than PoI,which significantly improves the block-out speed.When the percentage of malicious nodes reaches 70%,the binaryexponential backoff algorithm can still effectively reject malicious nodes,and the reliability of the system is fully guaranteed.

Key words: Blockchain, Dynamic grouping, Proof of Importance, Credit, DPoS