Blockchain-based decentralized trust management in IoT: systems, requirements and challenges

Internet of Things (IoT) vision has astoundingly transcended environmental sensing with integrated computing systems and smart devices, providing seamless connectivity among humans, machines, and their environment to cooperate for convenience and economical benefits. Apart from all the tremendous benefits of IoT, this paradigm still suffers from challenges of security and privacy vulnerabilities and demands a secure system for effective utilization of services in real-world IoT scenarios relying on which the IoT consumers expect secure and trustworthy communications. Trust Management (TM), which is a crucial aspect of security, plays a vital role in ensuring the exchange of information in a secure manner and maintaining the reliability of a system by measuring the degree of trust on IoT devices, reducing the uncertainties and risks involved in the systems. Thus, in recent years, Blockchain technology has been utilized for developing security innovations in TM field for different classes of IoT applications. It can provide tamper-proof data by enabling more reliable trust information and integrity verification, ultimately enhancing its availability and privacy when storing and sharing information. This paper provides a comprehensive survey that aims at analyzing and assessing Blockchain-based decentralized trust management systems (BCDTMS) for IoT. The contributions of this study are threefold; first, we provide the comprehensive and comparative analysis of state-of-the-art BCDTMS devised for different IoT classes such as Internet of Medical of Things (IoMT), Internet of Vehicles (IoV), Industrial IoT (IIoT), and Social IoT (SIoT). To make it an extensive study, we perform a detailed assessment of the existing BCDTMS in the literature in the aspects of Blockchain and TM. Second, we present requirements for developing Blockchain-based TM systems for IoT, and third we have highlighted the challenges in the context of using Blockchain for TM in various IoT applications.