FairDAG: Consensus Fairness over Multi-Proposer Causal Design

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 blockchain databases in which block proposers have full control over transaction ordering. To address this, a more fair approach to transaction ordering is essential. Existing fairness protocols, such as Pompe and Themis, operate on leader-based consensus protocols, which not only suffer from low throughput, but also allow adversaries to manipulate transaction ordering. To address these limitations, we propose FairDAG-AB and FairDAG-RL that run fairness protocols on top of DAG-based consensus protocols, which improve protocol performance in both throughput and fairness quality, leveraging the multi-proposer design and validity of DAG-based consensus protocols. We conducted a comprehensive analytical and experimental evaluation of our protocols. The results show that FairDAG-AB and FairDAG-RL outperform the prior fairness protocols in both throughput and fairness quality.