A Comprehensive Review of Blockchain and Distributed Ledger Integration in IoT: Consensus Mechanisms, Security Challenges and Future Directions

Abstract

The fast evolution of large-scale Internet of Things (IoT) networks has made it possible to develop intelligent applications in smart cities, healthcare, industry automation, transport, and nextgeneration communication systems. However, the conventional centralized architecture and security mechanisms are seriously challenged regarding scalability, latency, energy efficiency, trust management, and resilience against cyber-attacks in large-scale and heterogeneous IoT networks.Blockchain and Distributed Ledger Technologies (DLTs) provide promising solutions with the help of decentralization, immutability, and secure data sharing. However, the conventional consensus algorithms such as Proof of Work (PoW) and Proof of Stake (PoS) are not appropriate for large-scale IoT networks because of their high computational and communication complexities. This review provides a comprehensive analysis of the latest blockchain-based IoT solutions, with emphasis on lightweight, scalable, and energy-efficient consensus algorithms for largescale IoT networks. The latest and most advanced consensus algorithms, such as Delegated Proof of Stake (DPoS), Practical Byzantine Fault Tolerance (PBFT) variants, sharding-based systems, Directed Acyclic Graph (DAG)-based blockchain solutions, and agent-based DLT systems, are analyzed. The peer-reviewed literature is analyzed using quantitative performance analysis criteria such as throughput, latency, scalability, energy efficiency, and security resilience. The results show that although the new emerging lightweight and distributed ledger architectures have shown substantial improvements in performance and scalability in large-scale IoT networks, there are still important research challenges to be addressed in security robustness, interoperability, real-time processing, and real-world deployment validation. The research gaps are identified, and future research directions are presented in this review to develop new lightweight, secure, adaptive, and scalable blockchain-based architectures for next-generation large-scale IoT networks.