Research On Hybrid Consensus Algorithm Of High Performance Permissionless Blockchain

Blockchain technology has attracted wide attention due to the emergence of Bitcoin.With its decentralized and immutable features,value circulation and data sharing can be realized without third-party institutions,while privacy and security can be protected.Therefore,blockchain technology is regarded as the key technology for the information Internet to become a trusted Internet.As a kind of block chain,permissionless blockchain has a wide range of application scenarios because of its complete decentralization characteristics.Currently,the consensus algorithm applied to permissionless blockchain has the problems of low transaction throughput,high delay and lack of scalability.In order to solve these problems,this thesis studies the single committee and sharding consensus algorithms used in permissionless blockchain,mainly including the following aspects:Currently,in the consensus algorithm of single committee of permissionless blockchain,there are problems such as unfair election of committee members,lack of mechanism to guarantee the honest work of committee members,and relatively high complexity of communication among committee members.In view of the above shortcomings,we propose a consensus algorithm PL-BFT,which first uses a proof-of-work algorithm to generate an identity chain,selects a group of consensus committee on the identity chain and next the committee runs the Hot Stuff consensus algorithm to generate the transaction chain,which ensures complete decentralization and reduces the communication complexity at the same time,and rotates the committee members in each epoch.Finally,we replaced the threshold signature in Hot Stuff with the aggregate signature,and used the credit scoring mechanism to evaluate the verifiers in the committee.The verifiers with high credit scores could get more rewards at the end of the era.Through the theoretical analysis of the algorithm,the PL-BFT meets the security and activity.Experimental analysis shows that PL-BFT has higher transaction throughput and lower latency when the number of verifiers and malicious nodes is small.The existing multi-committee(sharding)consensus algorithm on the permissionless blockchain has the following problems: Nodes in each sharding need to store data redundantly to ensure the safety of distributed ledger,low transaction throughput,and complex sharding process brings security risks.In view of the above shortcomings,this thesis expands multiple identity chains,committees and transaction chains on the basis of PL-BFT,and forms a sharding consensus algorithm PL-MCC,which firstly uses Po W algorithm to quickly build shards,ensuring the security of each shard without relying on an honest third party,while reducing the complexity of communication.For intra-shard transactions,Hot Stuff algorithm was run to achieve consensus on the transaction.For cross-shard transactions,CPV was designed as a relay to achieve cross-shard consensus on the transaction.After the epoch ends,the shard is resharded to prevent malicious nodes from gathering in a shard and causing consensus failure.next,through theoretical analysis,our algorithm has security,less storage overhead and network connectivity,and satisfies the atomicity and final certainty of decentralization when transactions cross shards.Finally,the experimental test scheme is designed.Through the experimental analysis,our algorithm has a low delay,and the transaction throughput increases with the increase of fragmentation,realizing the scalability of the system.