  The Internet of Things (IoT) is revolutionizing human life with the idea of
interconnecting everyday used devices (Things) and making them smart. By
establishing a communication network between devices, the IoT system aids in
automating tasks and making them efficient and powerful. The sensors and the
physical world, connected over a network, involve a massive amount of data. The
data collection and sharing possess a critical threat of being stolen and
manipulated over the network. These inadequate data security and privacy issues
in IoT systems raise concerns about maintaining authentication of IoT data.
Blockchain, a tempter-resistant ledger, has emerged as a viable alternative to
provide security features. Blockchain technologies with decentralized
structures can help resolve IoT structure issues and protect against a single
point of failure. While providing robust security features, Blockchain also
bears various critical challenges in the IoT environment to adapt. This paper
presents a survey on state-of-the-art Blockchain technologies focusing on IoT
applications. With Blockchain protocols and data structures, the IoT
applications are outlined, along with possible advancements and modifications.
