Security and Performance Analysis of Quorum-based Blockchain Consensus Protocols

Abstract

Consensus protocols for blockchain-based systems are crucial and the most complex part of the blockchain. The proof-of-work consensus protocol of Bitcoin cryptocurrency is the most popular, but it presents a low transaction rate and high energy consumption. This paper analyzes the main quorum-based consensus protocols for blockchains that are alternatives with higher throughput and energy-efficient. The paper focuses on Byzantine fault-tolerant protocols as they are more robust to security attacks. We classify and analyze quorum-based consensus protocols according to their main characteristics and performance, highlighting the flaws and the specific attacks that affect each consensus protocol and presenting countermeasures. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup>