Privacy preservation in blockchain based IoT systems: Integration issues, prospects, challenges, and future research directions

Modern Internet of Things (IoT) systems are paving their path for a revolutionized world in which majority of our objects of everyday use will be interconnected. These objects will be able to link and communicate with each other and their surroundings in order to automate majority of our tasks. This interconnection of IoT nodes require security, seamless authentication, robustness and easy maintenance services. In order to provide such salient features, blockchain comes out as a viable solution. The decentralized nature of blockchain has resolved many security, maintenance, and authentication issues of IoT systems. Therefore, an immense increase in applications of blockchain-based IoT systems can be seen from the past few years. However, blockchain-based IoT network is public, so transactional details and encrypted keys are open and visible to everybody in that network. Thus, any adversary can infer critical information of users from this public infrastructure. In this paper, we discuss the privacy issues caused due to integration of blockchain in IoT applications by focusing over the applications of our daily use. Furthermore, we discuss implementation of five privacy preservation strategies in blockchain-based IoT systems named as anonymization, encryption, private contract, mixing, and differential privacy. Finally, we discuss challenges, and future directions for research in privacy preservation of blockchain-based IoT systems. This paper can serve as a basis of development of future privacy preservation strategies to address several privacy problems of IoT systems operating over blockchain. (C) 2019 Elsevier B.V. All rights reserved.