Consensus Algorithms in Blockchain: Comparative Analysis, Challenges and Opportunities

Blockchain is a distributed ledger that gained a prevalent attention in many areas. Many industries have started to implement blockchain solutions for their application and services. It is important to know the key components, functional characteristics, and architecture of blockchain to understand its impact and applicability to various applications. The most well-known use case of blockchain is bitcoin: a cryptocurrency. Being a distributed ledger, consensus mechanism is needed among peer nodes of a blockchain network to ensure its proper working. Many consensus algorithms have been proposed in literature each having its own performance and security characteristics. One consensus algorithm cannot serve the requirements of every application. It is vital to technically compare the available consensus algorithms to highlight their strengths, weaknesses, and use cases. We have identified and discussed parameters related to performance and security of consensus in blockchain. The consensus algorithms are analyzed and compared with respect to these parameters. Research gap regarding designing an efficient consensus algorithm and evaluating existing algorithms is presented. This paper will act as a guide for developers and researchers to evaluate and design a consensus algorithm.