The convergence of IoT and distributed ledger technologies (DLT): Opportunities, challenges, and solutions

Abstract Digital revolution is characterized by the convergence of technologies — from cloud computing to edge/fog computing, Artificial Intelligence (AI), big data, Intelligent Internet of Things (IoT), and Distributed Ledger Technology (DLT) — that is blurring the lines between physical and digital worlds. In this context, the IoT tsunami, the ubiquitous adoption of intelligent connected devices, and the public embracement of DLT, of which blockchain is a popular example, are increasingly becoming an integral feature of many modern systems, particularly, IoT-based smart and connected healthcare. Although the IoT and DLT/blockchain are two very different technologies and distinct from each other, the fusion of blockchain and IoT technologies is an unprecedented paradigm shift that is expected to disrupt both current and future systems in various fields. Blockchain has exactly what is needed to fix the weaknesses and vulnerabilities of IoT. It solves the security fault line among intelligent IoT where most of the IoT devices are connected to each other through the public trustless environment. Moreover, its distributed peer-to-peer nature can address the shortcomings of client/server models in Cloud-IoT solutions. Although the convergence of IoT and blockchain (Blockchain-IoT) can potentially tackle major shortcomings of today's solutions, its adoption is still in infancy, suffering from various issues and thus there is a necessity to address significant challenges including scalability, consensus algorithms, data privacy, efficiency, availability, storage, interoperability, and standardization, among others. In addition, there is no consensus towards any reference model or best practices that specify how blockchain should be utilized in IoT. This paper aims to present a holistic reference architecture as well as fundamentals, recent advancements, promises, and challenges in order to foster the investigations on cutting-edge research and allowing one to contribute to advancing the convergence of blockchain and IoT.