Permissioned Blockchains Interoperability: Theory, Practice and Industry 4.0 Applications

Blockchain technology has attracted considerable interest in recent years, both academically and in business. Its decentralisation, security, and transparency properties make it a disruptive technology of interest for the Industry 4.0 revolution. However, blockchains operate as isolated environments, unable to communicate with external systems. Finding ways to perform so-called inter-chain or cross-chain transactions, aimed at moving assets or data between different blockchains, is crucial for extending the functionality and applicability of this technology. Although numerous approaches exist for permissionless blockchain communication, interoperability issues are exacerbated in communication between permissioned blockchains, where stringent access control, data privacy, and governance mechanisms pose additional obstacles. This thesis analyses the most well-known interoperability protocols, highlighting their limitations and challenges. An ad-hoc protocol for interconnecting permissioned blockchains is then provided. The interoperability protocol aims to meet four essential requirements: efficiency, security, generalisability, and privacy. The novel solution will be analysed theoretically, discussing its safety and liveness properties in an eventually synchronous environment and in the presence of Byzantine failures. A prototype of the protocol will then be presented, on which some performance metrics such as latency in managing inter-chain transactions and throughput in terms of transactions per second will be computed. Finally, examples of blockchain applications for Industry 4.0 will be presented, and how interoperability is a catalyst for the integration of this technology into private contexts. It will be shown how blockchain can provide advantages in application areas such as the detection and control of pollutants inherent in industrial activities.