Blockchain networks are based on cryptographic notions that include asymmetric-key encryption, hash functions and consensus protocols. Despite their popularity, mainstream protocols, such as Proof of Work or Proof of Stake still have drawbacks. Efforts to enhance these protocols led to the birth of alternative consensus protocols, catering to specific areas, such as medicine or transportation. These protocols remain relatively unknown despite having unique merits worth investigating. Although past reviews have been published on popular blockchain consensus protocols, they do not include most of these lesser-known protocols. Highlighting these alternative consensus protocols contributes toward the advancement of the state of the art, as they have design features that may be useful to academics, blockchain practitioners and researchers. In this paper, we bridge this gap by providing an overview of alternative consensus protocols proposed within the past 3 years. We evaluate their overall performance based on metrics such as throughput, scalability, security, energy consumption, and finality. In our review, we examine the trade-offs that these consensus protocols have made in their attempts to optimize scalability and performance. To the best of our knowledge, this is the first paper that focuses on these alternative protocols, highlighting their unique features that can be used to develop future consensus protocols.

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区块链共识：替代协议概述

区块链网络基于加密概念，包括非对称密钥加密、哈希函数和共识协议。尽管它们很受欢迎，但主流协议（例如工作量证明或权益证明）仍然存在缺陷。加强这些协议的努力导致了替代方案的诞生共识协议，迎合特定领域，如医药或交通。尽管具有值得研究的独特优点，但这些协议仍然相对未知。虽然过去的评论已经发表在流行的区块链共识协议上，但它们并不包括大多数这些鲜为人知的协议。强调这些替代共识协议有助于推动最先进的技术发展，因为它们具有可能对学者、区块链从业者和研究人员有用的设计特征。在本文中，我们通过提供过去 3 年内提出的替代共识协议的概述来弥合这一差距。我们根据吞吐量、可扩展性、安全性、能耗和终结性等指标评估它们的整体性能。在我们的评论中，我们研究了这些共识协议在尝试优化可扩展性和性能时所做的权衡。据我们所知，这是第一篇专注于这些替代协议的论文，重点介绍了它们可用于开发未来共识协议的独特功能。