The blockchain is the technology behind the security of the first crypto currency, i.e., bitcoin. In addition to its decentralized nature, the blockchain is transparent, persistent, and secure. Blockchain is a technology that can overpower the security measures in internet of things (IoT). By using mathematics and cryptography techniques, blockchain provides an open decentralized database of every transaction, creating a record whose authenticity can be verified by the entire community. Blockchain technology can help to fill the security gaps in an IoT enabled network because it is not only reliable but also secure as blockchain practically makes it impossible to modify a historic transaction Blockchain technology is not a single working technique. It is a combination of several techniques which makes it suitable for any network. A summary of all the transaction in the block is kept in each block of blockchain using Merkle tree.