Research And Implementation Of Key Technologies Based On Hashgraph Blockchain Madel

In recent years,blockchain technology has been widely concerned by the government,financial institutions,science and technology industry because of its decentralized,tamper proof and strong security.However,its low transaction processing speed limits its further development in many applications.Therefore,this paper proposes a block chain model based on DAG structure,which transforms the original chain structure into DAG structure that can write transactions asynchronously and concurrently,and greatly improves the scalability of the system.Hashgraph is a typical innovation of DAG structure blockchain,which improves the transaction processing speed to million transactions per second.However,there are still many problems in practical application,such as complex consensus process,poor stability,and the system is greatly affected by node activity,processing capacity,bandwidth and other factors.This paper is committed to solve the above problems,and realizes the following parts:(1)Aiming at the problem of node lack of supervision in distributed system,a node reputation model is proposed.The model considers the performance of nodes in the system as the global reputation value of nodes,and combines it with the reward mechanism.Nodes with high reputation value get higher service fee when they provide the same number of services,which positively encourages nodes to actively provide services for the system.At the same time,a penalty factor is introduced to react to the behavior of nodes threatening the security of the system,which reduces the reputation value and increases the deterrent effect of the reputation model on nodes.(2)Aiming at the problem that bad nodes affect the efficiency of the system,a dynamic participation mechanism based on reputation is proposed.By introducing the role of judge,each node randomly selects the corresponding judge node based on the bloom filter,and the judge node is responsible for monitoring the change of the node's reputation value in real time.When the node's reputation value is lower than a certain threshold,the judge initiates the voting transaction to expel the node from the system.When more than half of the judge nodes send out the voting transaction,the judge node is removed from the system,and the decision is made New nodes can be introduced to replace them.It reduces the impact of nodes with poor performance on system efficiency.(3)Based on the reputation model,this paper creatively proposes a consensus algorithm based on Hashgraph.The algorithm introduces the leader role to simplify the consensus process,and realizes the leader selection algorithm based on verifiable random function.The algorithm makes the leader node random and unpredictable,and malicious nodes can not attack the leader node in advance,which ensures its security.Analysis and experiments show that the consensus algorithm can resist bifurcation attacks,and the consensus efficiency and throughput are significantly improved compared with virtual voting technology.