PhD defence of Anastasios Alexandridis – Improving Access Security and Throughput of Blockchain-based Internet of Things Infrastructure

The Internet of Things (IoT) has demonstrated promising growth, as it is crucial to numerous application domains in smart ecosystems, such as the smart city. Decentralization can help achieve growth, with previous research proposing the use of decentralized blockchain technology in IoT ecosystems as, among others, it can offer cryptographically trustworthy interactions, non-repudiable smart contracts, and interoperability between stakeholders.

However, blockchain-based IoT ecosystems come with challenges. Blockchain infrastructure may not be feasible due to architectural limitations resulting in inadequate performance. IoT communication and access to the blockchain also need securing, while system interoperability, efficiency, and cost are worth considering.

This thesis first proposes a security framework to secure multiple IoT systems simultaneously across heterogeneous platforms. It can secure communication and access to the blockchain through two-step authentication and encryption. The framework is designed and built into a multi-functional secure gateway that complies with security level 2 of the Federal Information Processing Standard (FIPS) 140-2.

Afterward, it explores the performance of blockchain and the difficulties in scaling through more conventional approaches, particularly for the private, permissioned blockchain. An enhancement addressing architectural limitations and the limited performance of blockchain infrastructure is proposed. A throughput increase is achieved through a multiple-layer network topology that partitions the blockchain network into hierarchical networks and allows blockchain transactions to be processed simultaneously.

Combining the secure gateway and multiple-layer network topology can achieve a secure, high-performing blockchain-based IoT infrastructure. In doing so, this thesis can help address the various challenges identified.