ABSTRACT
Blockchain is the emerging technology in the digital era. Blockchain is the extension of distributed concept and not a centralized storage that keeps track of blockchain data. In blockchain the data are stored over millions of computers around the world, and each node in a distributed environment is connected with the blockchain. The data stored in each node are publicly verifiable. Blockchain is defined as a “Non-corruptible digital ledger which can be programmed to record all the financial transactions”. In addition, it is also extended to keep track of the information that has value. Blockchain is considered as a list of blocks where each block contains a number of transactions. It provides a decentralized and immutable data store. Applications of blockchain can be extended to IoT, security, cloud, big data and the data analytics field. Blockchain technology acts as the backbone for Bitcoin. Bitcoin is known as a cryptocurrency, nothing but a form of electronic cash. It is also known as a decentralized digital currency. There is no centralized server or single bank that is responsible for its administration. Digital cash can be transferred from one user to another in a network without the involvement of an intermediary. These transactions are also updated to all participating entities in a network connected with blockchain. Bitcoin was invented by Satoshi Nakamoto in 2009 and released as open-source software. In Bitcoin a public ledger records the transactions of Bitcoins. A chain of blocks is implemented, and each block adds the hash value computed from the previous block up to a genesis block of the chain. Bitcoin software runs on all the communicating nodes in a network to maintain the blockchain. Every transaction is validated by the nodes of a network and a copy is added into their ledger, then broadcasted to others. Whenever the new technology emerges, the security of using it becomes doubtful, even though blockchain is designed to be immutable and tamper-proof. It achieves security through decentralization, cryptography and consensus concepts. Truth in blockchain is achieved through decentralization. If you change one block, you have to change all the subsequent blocks until any new blocks could be mined. Hashing techniques are used to hash the data cryptographically in a blockchain. It uses SHA-256 algorithm to produce a fixed-length hash value. Blockchain achieves this through cryptography primitives. Consensus helps to identify which node to add in a network. This part of the process is called proof of work (POW). It helps to ensure that each block is going through with vigorous mathematical processes before it becomes the immutable part of the blockchain. Blockchain is an emerging technology and it evolves every day. The vulnerabilities arise from the way in which how the blockchain interacts with other entities. In this chapter we will learn the importance of security concepts in blockchain. We will also explain how the CIA triad (confidentiality, integrity and authentication) is applied to blockchain in order to secure transactions and stored data.
