The rise of cryptocurrencies like Bitcoin and Ethereum has driven interest in blockchain database technology, with smart contracts enabling the growth of decentralized finance (DeFi). However, research has shown that adversaries exploit transaction ordering to extract profits through attacks like front-running, sandwich attacks, and liquidation manipulation. This issue affects blockchains where block proposers have full control over transaction ordering. To address this, a more fair transaction ordering mechanism is essential. Existing fairness protocols, such as Pompe and Themis, operate on leader-based consensus protocols, which not only suffer from low throughput caused by the single-leader bottleneck, but also allow adversarial block proposers to manipulate transaction ordering. To address these limitations, we propose a new framework, FairDAG, that runs fairness protocols on top of DAG-based consensus protocols. FairDAG improves protocol performance in both throughput and fairness quality by leveraging the multi-proposer design and validity property of DAG-based consensus protocols. We conducted a comprehensive analytical and experimental evaluation of two FairDAG variants - FairDAG-AB and FairDAG-RL. Our results demonstrate that FairDAG outperforms prior fairness protocols in both throughput and fairness quality.

翻译：比特币和以太坊等加密货币的兴起推动了区块链数据库技术的发展，智能合约促进了去中心化金融（DeFi）的成长。然而，研究表明攻击者利用交易排序通过抢先交易、三明治攻击和清算操纵等手段获取利润。这一问题主要影响那些由区块提议者完全控制交易排序的区块链。为解决此问题，建立更公平的交易排序机制至关重要。现有的公平协议（如Pompe和Themis）基于领导者共识协议运行，不仅存在单领导者瓶颈导致的低吞吐量问题，还允许恶意区块提议者操纵交易排序。为克服这些局限，我们提出了一种新框架FairDAG，该框架在基于有向无环图（DAG）的共识协议之上运行公平协议。FairDAG通过利用DAG共识协议的多提议者设计及有效性特性，在吞吐量和公平性质量两方面提升了协议性能。我们对两种FairDAG变体——FairDAG-AB与FairDAG-RL——进行了全面的理论与实验评估。结果表明，FairDAG在吞吐量和公平性质量上均优于现有公平协议。