Privacy-Oriented Blockchain-Based Distributed Key Management Architecture for Hierarchical Access Control in the IoT Scenario

The rapid development of the Internet of Things (IoT) and the explosive growth of valuable data produced by user equipment have led to strong demand for access control, especially hierarchical access control, which is performed from a group communication perspective. However, the key management strategies for such a future Internet are based mostly on a trusted third party that requires full trust of the key generation center (KGC) or central authority (CA). Recent studies indicate that centralized cloud centers will be unlikely to deliver satisfactory services to customers because we place too much trust in third parties; therefore, these centers do not apply to user privacy-oriented scenarios. This paper addresses these issues by proposing a novel blockchain-based distributed key management architecture (BDKMA) with fog computing to reduce latency and multiblockchains operated in the cloud to achieve cross-domain access. The proposed scheme utilizes blockchain technology to satisfy the decentralization, fine-grained auditability, high scalability, and extensibility requirements, as well as the privacy-preserving principles for hierarchical access control in IoT. We designed system operations methods and introduced different authorization assignment modes and group access patterns to reinforce the extensibility. We evaluated the performance of our proposed architecture and compared it with existing models using various performance measures. The simulation results show that the multiblockchain structure substantially improves system performance, and the scalability is excellent as the network size increases. Furthermore, dynamic transaction collection time adjustment enables the performance and system capacity to be optimized for various environments.