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    Developing a framework for prefabrication supply chain integration in New Zealand using blockchain technology : a thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy, Construction Project Management, School of Built Environment, College of Sciences, Massey University, Auckland, New Zealand
    (Massey University, 2024) Bakhtiarizadeh, Ehsan
    Prefabrication or off-site fabrication in New Zealand is snowballing in terms of its contribution to the delivery of construction projects. The increasing demand for new houses and the lack of affordable accommodations in New Zealand evolved the need for innovative and effective project delivery systems instead of conventional types. The prefabrication sub-sector is considered leverage for eliminating the shortcomings of traditional construction systems. However, this sub-sector of the construction industry struggles with challenges such as low coordination and integration across its supply chain partners. These challenges are attributed to the inefficient foundation of communication and information flow. This research addresses the problem of the relatively weak integration within New Zealand's prefabrication construction supply chain. The particular focus of the study is on information integration. The central point is that an effective and efficient exchange of information among supply chain stakeholders is imperative for enhancing supply chain integration in New Zealand's highly fragmented construction industry. Therefore, this study concludes that providing an effective information-integration-based platform for stakeholders involved in prefabrication projects will deliver integration improvement in the whole supply chain system. Blockchain technology, as a secure information integration instrument, capably improves the integration of information flow within the prefabrication sub-sector. Blockchain, a decentralised, safe, and unalterable information storage, offers numerous benefits to investors, clients, end-users, and other organisations or individuals. This technology, via its inherent features such as decentralisation, consensus mechanism, and immutability, supports organisations engaged in the supply chain with more transparent and trustful interactions and information flow. By adopting qualitative and quantitative data collection methods, this research provides insight into the applicability of blockchain technology within prefabrication construction supply chains. Minimum input requirements for blockchain according to types and patterns of information will be identified and categorised, and an applicable framework for using this new information integration technology will be proposed. Some key findings of this study are the identification and classification of (1) key stakeholders and recent project phases within the prefabrication supply chain, (2) flow of information across the stakeholders in different project phases, (3) important information attributes, (4) communication channels among stakeholders, and (4) impact of blockchain technology on facilitating information integration in the prefabrication construction industry of New Zealand. This research utilised pilot interviews, a questionnaire survey, a focus group study, and a validation survey to verify the objectives of the research and validate the proposed blockchain-based framework. The findings of this research could also be relevant to other industries facing similar challenges that rely heavily on information inputs. By identifying the importance of efficient information integration and the attributes crucial for successful project outcomes, stakeholders can prioritise investments in technologies like blockchain to streamline communication and data sharing across the supply chain. The identification of conventional communication modes like email, meetings, and internet-based applications in the prefabrication supply chain suggests a reliance on traditional methods for information exchange. However, the research underscores the importance of transparency, traceability, and reliability in communication, especially in the context of advanced information technology adoption. This implies a need for stakeholders to develop tailored communication strategies that leverage both conventional methods and emerging technologies to ensure effective collaboration throughout project phases. Finally, the development of a practical document management framework utilising blockchain technology presents opportunities for innovation and collaboration within the prefabrication industry. By demonstrating the applicability of blockchain in addressing document management challenges and validating the framework through expert feedback, the research paves the way for industry practitioners to adopt similar approaches in their projects. This suggests a broader trend towards embracing digital solutions and collaborative platforms to enhance information exchange, transparency, and project efficiency in the prefabrication sector.
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    Blockchain for secured IoT and D2D applications over 5G cellular networks : a thesis by publications presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Computer and Electronics Engineering, Massey University, Albany, New Zealand
    (Massey University, 2021) Honar Pajooh, Houshyar
    The Internet of things (IoT) is in continuous development with ever-growing popularity. It brings significant benefits through enabling humans and the physical world to interact using various technologies from small sensors to cloud computing. IoT devices and networks are appealing targets of various cyber attacks and can be hampered by malicious intervening attackers if the IoT is not appropriately protected. However, IoT security and privacy remain a major challenge due to characteristics of the IoT, such as heterogeneity, scalability, nature of the data, and operation in open environments. Moreover, many existing cloud-based solutions for IoT security rely on central remote servers over vulnerable Internet connections. The decentralized and distributed nature of blockchain technology has attracted significant attention as a suitable solution to tackle the security and privacy concerns of the IoT and device-to-device (D2D) communication. This thesis explores the possible adoption of blockchain technology to address the security and privacy challenges of the IoT under the 5G cellular system. This thesis makes four novel contributions. First, a Multi-layer Blockchain Security (MBS) model is proposed to protect IoT networks while simplifying the implementation of blockchain technology. The concept of clustering is utilized to facilitate multi-layer architecture deployment and increase scalability. The K-unknown clusters are formed within the IoT network by applying a hybrid Evolutionary Computation Algorithm using Simulated Annealing (SA) and Genetic Algorithms (GA) to structure the overlay nodes. The open-source Hyperledger Fabric (HLF) Blockchain platform is deployed for the proposed model development. Base stations adopt a global blockchain approach to communicate with each other securely. The quantitative arguments demonstrate that the proposed clustering algorithm performs well when compared to the earlier reported methods. The proposed lightweight blockchain model is also better suited to balance network latency and throughput compared to a traditional global blockchain. Next, a model is proposed to integrate IoT systems and blockchain by implementing the permissioned blockchain Hyperledger Fabric. The security of the edge computing devices is provided by employing a local authentication process. A lightweight mutual authentication and authorization solution is proposed to ensure the security of tiny IoT devices within the ecosystem. In addition, the proposed model provides traceability for the data generated by the IoT devices. The performance of the proposed model is validated with practical implementation by measuring performance metrics such as transaction throughput and latency, resource consumption, and network use. The results indicate that the proposed platform with the HLF implementation is promising for the security of resource-constrained IoT devices and is scalable for deployment in various IoT scenarios. Despite the increasing development of blockchain platforms, there is still no comprehensive method for adopting blockchain technology on IoT systems due to the blockchain's limited capability to process substantial transaction requests from a massive number of IoT devices. The Fabric comprises various components such as smart contracts, peers, endorsers, validators, committers, and Orderers. A comprehensive empirical model is proposed that measures HLF's performance and identifies potential performance bottlenecks to better meet blockchain-based IoT applications' requirements. The implementation of HLF on distributed large-scale IoT systems is proposed. The performance of the HLF is evaluated in terms of throughput, latency, network sizes, scalability, and the number of peers serviceable by the platform. The experimental results demonstrate that the proposed framework can provide a detailed and real-time performance evaluation of blockchain systems for large-scale IoT applications. The diversity and the sheer increase in the number of connected IoT devices have brought significant concerns about storing and protecting the large IoT data volume. Dependencies of the centralized server solution impose significant trust issues and make it vulnerable to security risks. A layer-based distributed data storage design and implementation of a blockchain-enabled large-scale IoT system is proposed to mitigate these challenges by using the HLF platform for distributed ledger solutions. The need for a centralized server and third-party auditor is eliminated by leveraging HLF peers who perform transaction verification and records audits in a big data system with the help of blockchain technology. The HLF blockchain facilitates storing the lightweight verification tags on the blockchain ledger. In contrast, the actual metadata is stored in the off-chain big data system to reduce the communication overheads and enhance data integrity. Finally, experiments are conducted to evaluate the performance of the proposed scheme in terms of throughput, latency, communication, and computation costs. The results indicate the feasibility of the proposed solution to retrieve and store the provenance of large-scale IoT data within the big data ecosystem using the HLF blockchain.