A comprehensive review of blockchain consensus algorithms

Blockchain is a disruptive innovation technology with a positive impact across various sectors. As it evolves, certain challenges arise that need addressing, including decentralization, security, and scalability. Each of the consensus algorithms (CA) that have been introduced so far attempt to address the blockchain trilemma and overcome these challenges. Yet, none of them have achieved optimum results. This chapter navigates this area and attempts to clarify much of the surrounding confusion. Initially, it reviews 20 well-known CA that are used in blockchains and analyzes them. The research reported herein reveals the need for an evaluation framework that can be used to assess CA As a result, the chapter proposes a suitable one that utilizes criteria such as decentralization, security, scalability, energy efficiency and fairness.