标题： 领导者轮换不足：审视链式BFT共识中的领导民主化 显示英文标题

标题： Leader Rotation Is Not Enough: Scrutinizing Leadership Democracy of Chained BFT Consensus

摘要： 随着区块链的日益流行，结合链式结构和领导者轮换以获得更好效率和领导民主性的现代链式BFT协议引起了越来越多的关注。 尽管链式BFT协议的效率条款已经得到了彻底分析，但先前的工作中对领导民主性的关注却很少。 在本文中，我们仔细研究了四种代表性链式BFT协议的领导民主性，尤其是在受到攻击的情况下。 为此，我们提出了一种统一的框架，包含两个评估指标，即链质量与审查弹性，并通过马尔可夫决策过程（MDP）对选定的协议进行定量分析。 借助这个框架，我们进一步检验了两个关键组件，即投票模式和领导者轮换对领导民主性的影响。 我们的结果表明，领导者轮换本身不足以提供领导民主性的保障；攻击者可以利用设计，例如投票模式，显著恶化领导民主性。 基于分析结果，我们为三种评估过的协议提出了定制的对策，以在仅略微增加协议开销且不改变共识规则的情况下提高它们的领导民主性。 我们还讨论了构建更民主的链式BFT协议的未来方向。 显示英文摘要

摘要： With the growing popularity of blockchains, modern chained BFT protocols combining chaining and leader rotation to obtain better efficiency and leadership democracy have received increasing interest. Although the efficiency provisions of chained BFT protocols have been thoroughly analyzed, the leadership democracy has received little attention in prior work. In this paper, we scrutinize the leadership democracy of four representative chained BFT protocols, especially under attack. To this end, we propose a unified framework with two evaluation metrics, i.e., chain quality and censorship resilience, and quantitatively analyze chosen protocols through the Markov Decision Process (MDP). With this framework, we further examine the impact of two key components, i.e., voting pattern and leader rotation on leadership democracy. Our results indicate that leader rotation is not enough to provide the leadership democracy guarantee; an adversary could utilize the design, e.g., voting pattern, to deteriorate the leadership democracy significantly. Based on the analysis results, we propose customized countermeasures for three evaluated protocols to improve their leadership democracy with only slight protocol overhead and no change of consensus rules. We also discuss future directions toward building more democratic chained BFT protocols.