A family of leaderless, decentralized consensus protocols, called Snow consensus was introduced in a recent whitepaper by Yin et al. These protocols address limitations of existing consensus methods, such as those using proof-of-work or quorums, by utilizing randomization and maintaining some level of resilience against Byzantine participants. Crucially, Snow consensus underpins the Avalanche blockchain, which provides a popular cryptocurrency and a platform for running smart contracts. Snow consensus algorithms are built on a natural, randomized routine, whereby participants continuously sample subsets of others and adopt an observed majority value until consensus is achieved. Additionally, Snow consensus defines conditions based on participants' local views and security parameters. These conditions indicate when a party can confidently finalize its local value, knowing it will be adopted by honest participants. Although Snow consensus algorithms can be formulated concisely, there is a complex interaction between randomization, adversarial influence, and security parameters, which requires a formal analysis of their security and liveness. Snow protocols form the foundation for Avalanche-type blockchains, and this work aims to increase our understanding of such protocols by providing insights into their liveness and safety characteristics. First, we analyze these Snow protocols in terms of latency and security. Second, we expose a design issue where the trade-off between these two is unfavorable. Third, we propose a modification of the original protocol where this trade-off is much more favorable.

翻译：一组称为雪崩共识的无领导者去中心化共识协议由Yin等人在近期白皮书中提出。这些协议通过引入随机化机制并保持对拜占庭参与者的抗性，解决了现有共识方法（如采用工作量证明或法定人数机制的方案）的局限性。雪崩共识作为雪崩区块链的核心支撑，该区块链既提供流行加密货币交易功能，又支持智能合约运行环境。雪崩共识算法建立在自然的随机化流程之上，参与者持续采样其他节点子集并采纳观察到的多数值，直至达成共识。此外，雪崩共识基于参与者的局部视图和安全参数定义了终止条件，这些条件表明某一方何时能确信其局部值最终将被诚实参与者采纳。尽管雪崩共识算法的表述简洁，但随机化机制、对抗性影响与安全参数之间存在复杂交互，这要求对其安全性与活跃性进行形式化分析。雪崩协议作为雪崩类区块链的基础，本研究旨在通过解析其活跃性与安全性特征来加深对该类协议的理解。首先，我们从延迟与安全性角度分析雪崩协议；其次，揭示其存在的设计缺陷——两者间的权衡关系欠佳；最后，提出对原始协议的改进方案，显著优化了该权衡关系。