Blockchain Meets IoT: What Needs To Be Addressed

University of Technology Sydney. Faculty of Engineering and Information Technology.The connection between Blockchain and Internet of Things (IoT) has no longer been futuristic. However, the research of Blockchain-based IoT is challenging. The traditional Blockchain technologies become gradually incapable of satisfying the growing market of IoT networks, and demand for significant improvements. This research proposes a variety of novel approaches, aiming to point out and address the key challenges from different aspects, i.e., consensus algorithms, Blockchain scalability, privacy/access control, and integration of the system. The main contributions of this thesis are summarized as follows. • This thesis proposes a Markov model explicitly capturing the weighted resource distribution of Proof-of-X (PoX) schemes in large-scale networks and unifying the analysis of different PoX schemes. The new model leads to the development of three new unified metrics for the evaluation, namely, Resource Sensitivity, System Convergence, and Resource Fairness, accounting for security, stability, and fairness, respectively. The generality and applicability of our model are validated by simulations in the context of the proposed metrics. • This thesis proposes detailed comparison and quantitative evaluation of major Blockchain-based sharding mechanisms in a systematic and comprehensive way. Specifically, the contents include our insights analyzing the features and restrictions of the existing solutions. We also provide theoretical upper-bound of the throughput for each considered sharding mechanism. The remaining challenges and future research directions are also reviewed. • This thesis proposes a new Blockchain-based IoT system which is compatible with attribute-based encryption (ABE) technique, and fine-grained access control is implemented with the attribute update enabled by integrating Chameleon Hash (CH) algorithms into the Blockchains. We design, and implement a new verification scheme over, a multi-layer Blockchain architecture to guarantee the tamper-resistance against malicious and abusive tampering. We also provide analysis and simulations showing that our system outperforms other solutions in terms of overhead, searching complexity, security, and compatibility. • This thesis proposes a novel Dual-Blockchain-based Long Range (LoRa) system providing global cross-validated security, as a case study of integration between Blockchain and IoT. The rational behaviours of participators, the state-of-the-art contract-theoretic incentive mechanism, and the newly-designed flow control protocol, can be secured by the tamper-resistance of Blockchains. Being part of the proposed incentive mechanism, the self-driven flow control scales both the Dual-Chain system and the LoRa network. We provide analysis and simulations showing that the system motivates the self-deployed LoRa Gateways in a more secure way, thus optimize the utilization of coverage while improving the Blockchain scalability and flexibility