Abstract
Recently, the IoT environment is becoming more fertile for malicious users to break the security and privacy of users. Access control becomes a critical requirement to protect against illegal access that usually leads to sensitive data leakage. Unfortunately, the traditional access control mechanisms are centralized in terms of design and management, thus are not suitable for decentralized IoT systems. To deal with the distributed IoT environment, blockchain is considered as a promising distributed data management technology to different non-crypto currency areas, including IoT. Although blockchain can optimize some IoT requirements such as dynamicity, security, decentralization, and anonymity, it has some issues such as complex consensus algorithms, overhead, and scalability. This paper surveys and compares the most recent researches in the blockchain-based access control for IoT and suggests a set of requirements that should be considered while applying blockchain to control access in the IoT environment.