Nakamoto共识是世界上许多最大的加密货币（如比特币和以太坊）安全性的基础。常见的说法是，Nakamoto共识只在其底层挖掘难题的难度非常高的情况下才能实现一致性和活性，从而对整体吞吐量和延迟产生负面影响。在这项工作中，我们研究了中本聪共识下广泛的难题的困难，包括非常容易的难题。我们首先分析了一个无对手的设置，并表明，令人惊讶的是，即使是简单的谜题，区块链的公共前缀也会迅速增长。在有对手的情况下，我们对Nakamoto共识进行了一个小的向后兼容的更改，以通过简单的谜题实现一致性和活跃性。我们的洞察力依赖于仔细选择\emph{symmetry-breaking strategy}，这在以前的工作中被大大低估了。本文提出了一种新的方法- \emph{coalescing random walks} --来分析一致性策略下Nakamoto共识的正确性。该方法比现有的集中于限制{ \it收敛机会}的数量的分析方法更强大。
英文摘要：
Nakamoto consensus underlies the security of many of the world's largest cryptocurrencies, such as Bitcoin and Ethereum. Common lore is that Nakamoto consensus only achieves consistency and liveness under a regime where the difficulty of its underlying mining puzzle is very high, negatively impacting overall throughput and latency. In this work, we study Nakamoto consensus under a wide range of puzzle difficulties, including very easy puzzles. We first analyze an adversary-free setting and show that, surprisingly, the common prefix of the blockchain grows quickly even with easy puzzles. In a setting with adversaries, we provide a small backwards-compatible change to Nakamoto consensus to achieve consistency and liveness with easy puzzles. Our insight relies on a careful choice of \emph{symmetry-breaking strategy}, which was significantly underestimated in prior work. We introduce a new method -- \emph{coalescing random walks} -- to analyzing the correctness of Nakamoto consensus under the uniformly-at-random symmetry-breaking strategy. This method is more powerful than existing analysis methods that focus on bounding the number of {\it convergence opportunities}.
HYDRA: Breaking the Global Ordering Barrier in Multi-BFT Consensus
University of British Columbia（不列颠哥伦比亚大学）；University of California, Davis（加州大学戴维斯分校）；City University of Hong Kong（香港城市大学）；Southern University of Science and Technology（南方科技大学）
University of British Columbia（不列颠哥伦比亚大学）；SUSTech（南方科技大学）；Research Institute of Trustworthy Autonomous Systems of SUSTech（南方科技大学可信自主系统研究院）；City University of Hong Kong（香港城市大学）；National University of Singapore（新加坡国立大学）
