面向物联网的区块链共识机制综述

随着数字货币的不断发展，区块链技术引起越来越多人的关注，而对其关键技术共识机制的研究尤为重要。将区块链技术应用在物联网（IoT）中是目前研究的热点问题之一。共识机制是区块链的核心技术之一，其在去中心化程度、交易处理速度、交易确认延迟、安全性以及可扩展性等方面对IoT产生了重要影响。首先对IoT的体系结构特征以及资源受限问题造成的轻量化问题作了阐述，对在IoT中实现区块链所面临的问题作了简要概述，并结合比特币的运行流程对IoT中的区块链需求进行了分析；其次，把共识机制分为证明类、拜占庭类和有向无环图（DAG）类，研究了这些不同类别的共识机制的工作原理，在通信复杂度上分析它们与IoT的适应度，总结它们的优缺点，并对现有的共识机制和IoT结合的架构进行了调研分析；最后，针对IoT面临的中心机构运行成本高、可扩展性差、安全性存在隐患等问题进行了深入研究，分析结果表明，基于DAG技术的埃欧塔（IOTA）和Byteball共识机制在交易数量很多的情况下具有交易处理速度快、可扩展性好、安全性强的优点，是未来IoT领域区块链共识机制的发展方向。

Overview of blockchain consensus mechanism for internet of things

With the continuous development of digital currency, the blockchain technology has attracted more and more attention, and the research on its key technology, consensus mechanism, is particularly important. The application of blockchain technology in the Internet of Things(IoT) is one of the hot issues. Consensus mechanism is one of the core technologies of blockchain, which has an important impact on IoT in terms of decentralization degree, transaction processing speed, transaction confirmation delay, security, and scalability.Firstly, the architecture characteristics of IoT and the lightweight problem caused by resource limitation were described, the problems faced in the implementation of the blockchain in IoT were briefly summarized, and the demands of blockchain in IoT were analyzed by combining the operation flow of bitcoin. Secondly, the consensus mechanisms were divided into proof class, Byzantine class and Directed Acyclic Graph(DAG) class, and the working principles of these various classes of consensus mechanisms were studied, their adaptabilities to IoT were analyzed in terms of communication complexity, their advantages and disadvantages were summarized, and the combination architectures of the existing consensus mechanisms and IoT were investigated and analyzed. Finally, the problems of IoT, such as high operating cost, poor scalability and security risks were deeply studied, the analysis results show that the Internet of Things Application(IOTA) and Byteball consensus mechanisms based on DAG technology have the advantages of fast transaction processing speed, good scalability and strong security in the case of having a large number of transactions, and they are the development directions of blockchain consensus mechanism in the field of IoT in the future.