Research On Sybil Attack Defense Method In Blockchain Based On Improved PBFT Algorithm

With the increasing attention of the blockchain technology,the security issues of the blockchain technology in practical applications are becoming increasingly important.Blockchain technology is essentially a decentralized database,which shows huge potential application value in many aspects such as finance,medical treatment,logistics and transportation,etc.However,because the network architecture in the blockchain uses P2 P network architecture,it is vulnerable to Sybil attacks.The Sybil attack is a malicious node that joins the blockchain network by forging multiple false identities and attempts to have a bad impact on the network.It usually cooperates with the Eclipse attack to launch the attack.When normal nodes in the blockchain are attacked,no matter the request information sent or received may be intercepted and tampered by the Sybil node.If the information received by the normal node is tampered with by the Sybil node,then normal operation cannot be performed.The consensus process destroys the topology of the network and prevents nodes in the blockchain from reaching consensus,thereby seeking illegal benefits for themselves.The Sybil attacks not only destroy the security of resource sharing in the P2 P network,consume the computing resources of normal nodes,and even control the entire network system in severe cases,so this attack has extremely harmful to the blockchain technology.In order to defend against Sybil attacks in the blockchain,by improving the PBFT algorithm,a method of defense against Sybil attacks in the blockchain based on the improved PBFT algorithm is proposed.The main research contents of this article are as follows:(1)The improved design of the PBFT consensus algorithm proposed in this paper draws on the idea of a consensus algorithm based on Proof of Stake(POS).The reputation value of node is related to the voting weight of the node in the consensus process.By establishing a reputation model among blockchain nodes,the reputation value of a node is calculated based on the behavior of each node in the consensus process,and different discourse rights are given to nodes according to the reputation value.(2)At the same time,a Pre-Commit phase is added to the improved PBFT consensus algorithm to reduce the number of communication between nodes and improve the efficiency of consensus between nodes.Then according to the size of the reputation value and the trust status,the problematic master node is updated in the consensus process,and the node with the highest reputation value is selected as the master node.(3)Finally,the improved consensus protocol is formally proven.Through experiments,it is proved that the improved consensus protocol is still secure and can effectively prevent Sybil attacks in the blockchain.