Blockchain is a new technology that is recently been used in many different applications, including Bitcoin, supply chain management, smart grid, health care, and smart farming. Numerous studies have been conducted in this area recently. IoT is critical to the advancement of various fields. IoT networks are expanding in terms of the number of devices linked and the system’s size and complexity. There are numerous challenges in IoT, including security, availability, dependability, and authentication. Blockchain technology has the ability to solve challenges in the Internet of Things ecosystem. Blockchain’s main characteristics are transparency, security, immutability, traceability, and so on. A thorough examination of blockchain characteristics and applications was conducted by many researchers. We organise and summarise the work that has been done in this area. An architectural design for integrating blockchain and IoT is also presented, ensuring distributed data storage, authentication, and processing and an algorithm for registering IoT devices to the blockchain is also proposed.