基于哈希图的建筑物联网数据管理方法

针对区块链应用于建筑物联网场景时存在的吞吐量严重不足和响应时延高的问题，提出一种基于哈希图的建筑物联网数据管理方法。该方法使用有向无环图（DAG）存储数据，从而利用图式结构的高并发特性提高区块链的吞吐量性能；引入哈希图算法对存储在DAG内的数据达成共识，从而减少共识所需时间；设计智能合约实现访问权限控制，以防止未授权用户对数据的操作。使用区块链性能测试工具Caliper进行的性能测试的结果表明：在由32个节点构成的中等规模仿真环境下，与现有边缘计算方法和跨链方法相比，所提方法的吞吐量为每秒处理1 063.1笔交易，分别为对比方法吞吐量的6倍和3倍；该方法的数据存储时延和控制时延分别为4.57 s和4.92 s，响应速度优于对比方法；该方法在尖峰冲击测试中的交易成功率为87.4%；同时基于该方法的原型系统在稳定性测试中可以平稳运行120 h。可见，所提方法可以有效提高区块链的交易吞吐量和响应速度，满足建筑物联网场景的实际使用需求。

Data management method for building internet of things based on Hashgraph

A Hashgraph-based data management method for building Internet of Things （IoT） was proposed to address the problems of severe lack of throughput and high response delay when applying blockchain to the building IoT scenarios. In this method， Directed Acyclic Graph （DAG） was used for data storage to increase the throughput performance of blockchain because of the high concurrency of schematic structure； Hashgraph algorithm was applied to reach consensus on the data stored in DAG to reduce the time consumption of consensus； the smart contracts were designed to realize access control to prevent unauthorized users from operating data. Caliper， a blockchain performance testing tool， was adopted for performance test. The results show that in a medium-scale simulation environment with 32 nodes， the throughput of the proposed method is 1 063.1 transactions per second， which is 6 times and 3 times than that of the edge computing and the cross-chain methods； the data storage delay and control delay of the proposed method are 4.57 seconds and 4.92 seconds respectively， indicating that the proposed method has the response speed better than the comparison methods； and the transaction success rate of this method reaches 87.4% in spike testing. At the same time， the prototype system based on this method can run stably for 120 hours in stability testing. The above illustrates that the proposed method can effectively improve the throughput and response speed of blockchain， and meets actual needs in the building IoT scenarios.