Abstract: With the rapid development of blockchain technology,blockchain faces scalability challenges in terms of storage overhead and data throughput.The blockchain is affected by the consensus principle of overall consensus,and the global ledger of the entire blockchain needs to be stored between nodes,and the data storage overhead is high.At the same time,in order to maintain the consistency and credibility of transactions within the block,all nodes participate in the process of transaction verification and synchronization,the block synchronization delay in the peer-to-peer network is high.And the bandwidth requisition is blocked,which further reduces the data throughput.In response to these problems,this paper proposes a blockchain-based dual-branch structure expansion model.First,a ternary storage expansion structure of the blockchain is established.The nodes accurately divide the storage tasks and store the single,partial,and global ledger of the blockchain,which effectively reduces the storage burden of the nodes.Secondly,a dual-branch structure model is proposed,the main chain is divided into multi-channel sub-chains.And data is stored in parallel through multi-channel sub-chains,which significantly improves the data storage rate.Aiming at the compatibility problem of sub-chains after shunting,a two-way rotation mechanism is introduced to realize the fusion transition between chain structures.For the security problem of sub-chains after shunting,the gambler extension-F and gambler extension-S strategies are proposed to simulate the security attack of the two chain structures,and the mathematical modeling of the attack process is carried out.Finally,constructing the security constraints of the two models to verify the security of the dual-branch model.Experiments show that the dual-branch structure expansion model proposed in this paper can effectively resist malicious double-spending attacks,and has great advantages in storage overhead and data throughput.

Key words: Blockchain expansion, Two-degree branch chain, Ternary storage expansion, Two-way rotation mechanism, Gambler expansion mode