ABSTRACT
A blockchain is a cryptographically signed transactional record shared by the participating nodes in the network. Each record has a timestamp and link to earlier transactions, and it is a predominant architectural design of the distributed ledger concept. The authorized participant with proper access rights can track the history of transactional events belonging to any participant. However, a significant disconnect occurs between the expectation in the market sector and reality. Blockchain consensus protocols assure that the nodes in the network will be synchronized with each other. Consensus means the nodes in the blockchain network will agree on the same state for self-auditing across a distributed network. The main objective of the consensus protocol is to ensure a single chain is utilized and followed, and it is one of the significant revolutionary aspects of blockchain technology. Achieving consensus is an acceptance among nodes on the network for a data value even if some nodes are unreliable. The cryptocurrency must be secured against attacks in the blockchain, and it does not rely on a single centralized authority for security, where the users do not have any prior knowledge about the versions of the valid record. According to Gartner report, there will be an exponential growth of blockchain by 2020 due to the implementation of the smart contract which includes tokenization and decentralization. Furlonger said, “Blockchain is not just a technology, it is a societal change”. Consensus protocols provide rewards and incentives for the participants who are maintaining the blockchain. The rewards in blockchain will be in the form of tokens or cryptocurrencies, and the competition for confirming the next block in the chain is extremely high. The complete history of transaction is maintained in digital currencies to check the user’s balance at any time. Some of the significant objectives of blockchain consensus models are in achieving agreement, cooperation, collaboration, participation and activity. The different types of consensus algorithms are proof of work (PoW), proof of stake (PoS), delegated proof of stake (DPoS), leased proof of stake (LPoS), proof of elapsed time (PoET), practical Byzantine fault tolerance (PBFT), simplified Byzantine fault tolerance (SBFT), delegated Byzantine fault tolerance (DBFT), directed acyclic graphs (DAG), proof of activity (PoA), proof of importance (PoI), proof of capacity (PoC), proof of burn (PoB) and proof of weight (PoWeight). This chapter highlights the significance of consensus algorithms and their usage.
