Basing Diversified Services of Complex IIoT Applications on Scalable Block Graph Platform

In complex Industrial Internet of Things (IIoT) application systems, there may exist a variety of functional sub-systems which provide divergent services to the users and the relationship among these services could be strong, which is evidently very common in practice. As one such IoT application, the smart city is designed to use intelligent services in an environment where transport, environment, energy, living, governance, and civic components are integrated to operate the city in a smart and efficient manner. Surprisingly, however, the current state-of-the-art on blockchain does not show the progress on diversified services of the complex IIoT applications. This paper tends to fill the gap and presents a scalable block graph platform and consensus protocol for the complex IIoT applications by adopting the limited resources of IIoT devices. The platform and consensus protocol are generic in the sense that they can support any practical service. The directed acyclic graph represents a significant exhibition in improving the scalability of blockchains and supports our proposed consensus protocol in substance; moreover, the detailed syntax of the block graph is defined. The consensus protocol is showed to be secure against disloyal voting, sybil attack, and 51% attack. The real use case of smart city demonstrates the effectiveness of the proposal.