Research On Consensus Algorithm For Large-scale IoT Blockchain Based On Byzantine Fault Tolerance

Since the birth of Bitcoin in 2008,blockchain technology has been one of the most concerned research hotspots.With the help of cryptography technology and consensus algorithm,it can eliminate the dependence on the central server,and can ensure that the data is open and transparent,and cannot be tampered with.At present,the application of blockchain in the fields of supply chain and digital copyright has become relatively mature.Due to the single point of failure problem in the traditional IoT architecture,many applications of the combination of IoT and blockchain have emerged.However,since IoT devices frequently have limited computing and storage resources,this combination faces many problems in practical implementation The lack of a suitable consensus algorithm is a key point that cannot be ignored.We propose a highly scalable hybrid two-layer Byzantine fault-tolerant algorithm for blockchain applications in the IoT environment,and demonstrate experimentally its advantages of low required communication overhead and low consensus latency.Main contributions of this paper are as follows:1.A modified version of the clustering algorithm is used in this scheme,which groups the devices involved in consensus according to their geographical location in a reasonable way.It can make the distance between the nodes in the group as close as possible,minimizing the energy consumption of intra-group communication and making this scheme more suitable for the IoT environment.We layer the consensus according to the above grouping structure,reducing communication complexity from O(n2)to O(n4/3)and greatly improving the consensus algorithm’s scalability.2.The Weighted Asynchronous Byzantine Agreement(WABA)algorithm is proposed according to the structural characteristics of the grouped system.We provide a rigorous proof of the conditions that the algorithm needs to satisfy.The intragroup communication is relatively stable,so we use the PBFT algorithm in the first layer.The message delivery time between group leaders varies considerably due to the relatively long distance.We use the WABA algorithm in the second layer with the help of ideas in asynchronous consensus.This hybrid two-layer consensus combination fully exploits the advantages of these two consensus algorithms.3.In the second-level consensus,the group leader will attach a weight representing the consensus of the group members,and provide the group members’ signatures on the voting results to prevent evil.The group leader uses certificateless aggregated signatures to aggregate multiple signatures,which can effectively reduce the communication overhead and computational overhead in the verification phase.The certificateless cryptography does not need to introduce a completely trusted third party,but it has the disadvantage of requiring pre-broadcasting of the public key.Because of its transparent and open nature,blockchain can be seen as a platform for information sharing,making up for the shortcomings of certificateless cryptography.In order to prevent all kinds of node mischief,the concepts of"trusted groups" and "affiliated groups" are introduced,all error cases are analysed and dealt with,and a security and feasibility analysis is subsequently given.