Blockchain fragment expansion algorithm tolerant of high proportion of Byzantine nodes

• 1、Dalian Maritime University School, information science and technology University, Dalian 116026

Abstract：Expansion is a core requirement that urgently needs to be broken through in the broad application prospects of blockchain technology. Sharding is an important technology that the most hopes to solve the problem of blockchain expansion without reducing decentralization. When Practical Byzantine Fault Tolerance (PBFT) consensus algorithm is used in sharding, the restriction that "the proportion of BFT nodes must be less than 1/3, the proportion of Byzantine nodes in the sharding may also exceed 1/3. How to use the PBFT consensus algorithm in sharding to tolerate the situation where more than 1/3 of the nodes in the sharding may actually be Byzantine nodes, is the focus of this article. To this end, this article proposes a multi-round BFT algorithm MRBFT (Multi-Round BFT). First, this paper discusses the feasibility of the MRBFT consensus algorithm in the sharding against collusion attacks and effective verification. When the proportion of Byzantine nodes in the network is very high, such as 51%, the application of the MRBFT algorithm may cause too many rounds and large delays. Second, by partitioning the nodes in the sharding, the Byzantine nodes and the non-Byzantine nodes are partitioned, and an improved multi-round partition consensus algorithm PMRBFT (Partitioning Multi-Round BFT) is obtained, which optimizes the MRBFT algorithm above greatly, and reduces the number of actual verification rounds. Finally, experimental verification shows that even if the overall proportion of Byzantine nodes in the blockchain system reaches 51%, the PMRBFT algorithm can still reach an effective consensus in the sharding.

Keywords： Computer application Blockchain sharding PBFT consensus Byzantine node