Research On Block Chain Proof-of-work Consensus Algorithm

Proof-of-work/PoW consensus algorithms have been one of the top research directions since the inception of blockchain technology in 2008.Related researches show that blockchain protocols based on Po W consensus algorithm have shortcomings such as high variance in block interval time,high variance in reward for miners mining solo,increasing tendency to centralization and low throughput.In recent years,a series of beautiful Po W consensus algorithm-based blockchain protocols have been proposed to address the above shortcomings.However,there is no solution yet to address both the high variance of block interval time and the high variance of miners' solo mining reward.Moreover,scalable blockchain protocols based on the Po W consensus algorithm are increasingly complex and security is difficult to guarantee.Designing more secure,robust and highthroughput Po W consensus algorithm-based blockchain protocols is an area of significant research.This thesis focuses on the PoW consensus algorithm and the main contributions are as follows:(1)In this thesis,we propose LVRT:Low Variances of Solo Mining Reward ? Interblock Time in Collaborative Po W,which is used to solve the drawbacks of high variance in block interval time,high variance in miners' solo mining rewards,and centralization.The theoretical analysis concludes that the variance of miner solo mining reward in LVRT is lower than that of Strong Chain(USENIX Security 2019)proposed by Szalachowski et al.and is more decentralized.The theoretical analysis yields that the variance of the LVRT block interval time is approximately the same as that of Bobtail(NDSS 2020)proposed by Bissias et al.and the experiments validate this conclusion.The experiments in this thesis show that LVRT is effective in resisting selfish mining and double-spend attacks.(2)In this thesis,we propose Sib Cha: Simple Multi-Chain Blockchain Scaling Protocol in response to the limitations of current blockchain scalability protocols based on the Po W consensus algorithm,which are increasingly complex and difficult to guarantee security.The Sib Cha block structure and block confirming rules are simpler than OHIE(S?P 2020)proposed by Yu et al.and handle cross-chain transactions more simply than Monoxide(USENIX Security 2019)proposed by Wang et al.Chain-growth,chain-quality and consistency(i.e.persistence and liveness)are demonstrated in Sib Cha.Experiments show that Sib Cha throughput increases linearly with network bandwidth,and that block confirmation latency is lower than that of OHIE.