  Blockchain was mainly introduced for secure transactions in connection with
the mining of cryptocurrency Bitcoin. This article discusses the fundamental
concepts of blockchain technology and its components, such as block header,
transaction, smart contracts, etc. Blockchain uses the distributed databases,
so this article also explains the advantages of distributed Blockchain over a
centrally located database. Depending on the application, Blockchain is broadly
categorized into two categories; Permissionless and Permissioned. This article
elaborates on these two categories as well. Further, it covers the consensus
mechanism and its working along with an overview of the Ethereum platform.
Blockchain technology has been proved to be one of the remarkable techniques to
provide security to IoT devices. An illustration of how Blockchain will be
useful for IoT devices has been given. A few applications are also illustrated
to explain the working of Blockchain with IoT.
