基于区块链与边缘计算的物联网访问控制模型

边缘计算的出现扩展了物联网（IoT）云-终端架构的范畴，在减少终端设备海量数据的传输和处理时延的同时也带来了新的安全问题。针对IoT边缘节点与海量异构设备间的数据安全和管理问题，并考虑到目前区块链技术广泛应用于分布式系统中数据的安全管理，提出基于区块链与边缘计算的IoT访问控制模型SC-ABAC。首先，提出集成边缘计算的IoT访问控制架构，并结合智能合约和基于属性的访问控制（ABAC）提出并设计了SC-ABAC；然后，给出工作量证明（PoW）共识算法的优化和SC-ABAC的访问控制管理流程。实验结果表明，所提模型对区块连续访问下的耗时随次数呈线性增长，连续访问过程中央处理器（CPU）的利用率稳定，安全性良好。本模型下仅查询过程存在调用合约的耗时随次数呈线性增长，策略添加和判断过程的耗时均为常数级，且优化的共识机制较PoW每100块区块共识耗时降低约18.37个百分点。可见，该模型可在IoT环境中提供去中心化、细颗粒度和动态的访问控制管理，并可在分布式系统中更快达成共识以确保数据一致性。

Internet of things access control model based on blockchain and edge computing

The emergence of edge computing has expanded the scope of Internet of Things （IoT） cloud-terminal architecture. With the reduction of transmission and processing delays of massive data on terminal devices， it also brings new security issues. Aiming at the problem of data security and management issues between edge nodes of IoT and massive heterogeneous devices， and considering that blockchain technology is widely used in the security management of data in distributed systems， an IoT access control model Smart Contract for Attribute-Based Access Control （SC-ABAC） was proposed based on blockchain and edge computing. Firstly， an IoT access control architecture integrated with edge computing was proposed， and by combining smart contracts with Attribute-Based Access Control （ABAC）， SC-ABAC was proposed and designed. Then， the optimization of Proof of Work （PoW） consensus algorithm and the access control management flow of SC-ABAC were given. Experimental results show that the time consumed by the proposed model increases linearly with the number of times under continuous access to the block， the Central Processing Unit （CPU） utilization rate is stable， and the CPU security is good during the continuous access process. In this model， the time consumption of calling contracts in the query process only increases linearly with the times， and the time consumptions of the strategy addition and judgment process are both constant. And the optimized consensus mechanism has about 18.37 percentage points less time consumption than PoW consensus per 100 blocks. Therefore， the proposed model can provide decentralized， fine-grained and dynamic access control management in the IoT environment， and can reach consensus faster in a distributed system to ensure data consistency.