Vote-based blockchains construct a state machine replication (SMR) system among participating nodes, using Byzantine Fault Tolerance (BFT) consensus protocols to transition from one state to another. Currently, they rely on either synchronous or partially synchronous networks with leader-based coordination or costly Asynchronous Common Subset (ACS) protocols in asynchronous settings, making them impractical for large-scale asynchronous applications. To make Asynchronous SMR scalable, this paper proposes a \emph{validated strong} BFT consensus model that allows leader-based coordination in asynchronous settings. Our BFT consensus model offers the same level of tolerance as binary byzantine agreement but does not demand consistency among honest nodes before they vote. An SMR using our model allows nodes to operate in different, tentative, but mutually exclusive states until they eventually converge on the same state. We propose an asynchronous BFT protocol for vote-based blockchains employing our consensus model to address several critical challenges: how to ensure that nodes eventually converge on the same state across voting rounds, how to assure that a blockchain will steadily progress through epochs while reaching consensus for previous epochs, and how to maintain robust byzantine fault tolerance. Our protocol greatly reduces message complexity and is the first one to achieve linear view changes without relying on threshold signatures. We prove that an asynchronous blockchain built on our protocol can operate with the \emph{same} simplicity and efficiency as partially synchronous blockchains built on, e.g. HotStuff-2. This facilitates deploying asynchronous blockchains across large-scale networks.

翻译：基于投票的区块链在参与节点间构建状态机复制系统，利用拜占庭容错共识协议实现状态转换。现有方案要么依赖同步或部分同步网络并采用基于领导者的协调机制，要么在异步环境中采用高成本的异步公共子集协议，使其难以适用于大规模异步应用。为实现异步状态机复制的可扩展性，本文提出一种验证强拜占庭容错共识模型，该模型支持在异步环境下进行基于领导者的协调。我们的拜占庭容错共识模型提供与二元拜占庭协议相同的容错能力，但无需诚实节点在投票前达成状态一致性。采用本模型的状态机复制系统允许节点在最终收敛至相同状态前，运行于不同、暂定且互斥的状态。我们提出一种采用本共识模型的异步拜占庭容错协议，以解决若干关键挑战：如何确保节点在多个投票轮次后最终收敛至相同状态，如何保证区块链在推进纪元更迭的同时完成对历史纪元的共识，以及如何维持鲁棒的拜占庭容错能力。本协议大幅降低消息复杂度，并首次在不依赖门限签名的情况下实现线性视图切换。我们证明基于本协议构建的异步区块链能够以与部分同步区块链（如HotStuff-2）相同的简洁性和效率运行，这将促进异步区块链在大规模网络中的部署。