Over recent years, the blockchain ecosystem has grown significantly with the emergence of new Layer-1 (L1) and Layer-2 (L2) networks. These blockchains typically host Decentralized Exchanges (DEXes) for trading assets such as native currencies and stablecoins. While this diversity enriches the ecosystem, it also fragments liquidity, posing challenges for DEXes offering the same assets across multiple blockchains. This fragmentation leads to price discrepancies, creating opportunities like arbitrages for profit-seeking traders, which fall under the broader category of exploitative economic practices known as Maximal Extractable Value (MEV). Although MEV extraction has been extensively studied within single domains (i.e., individual blockchains), cross-chain arbitrages, a form of cross-domain MEV, have received little attention due to their non-atomic nature, complicating both execution and detection. In this paper, we shed light on opaque cross-chain MEV activities by presenting the first systematic study of two non-atomic cross-chain arbitrage strategies: Sequence-Independent Arbitrage (SIA) and Sequence-Dependent Arbitrage (SDA). The former involves independent, opposite-direction trades across chains, while the latter relies on asset bridges. We analyze the effectiveness of these strategies across nine blockchains over a one-year period from September 2023 to August 2024, identifying 260,808 cross-chain arbitrages, 32.37% of which involve bridging solutions. These arbitrages generated a lower-bound profit of 9,496,115.28 USD from a total traded volume of 465,797,487.98 USD. Additionally, we examine the security implications of cross-chain arbitrages, uncovering centralization among arbitrageurs, network congestion caused by failed transactions, and growing private mempool adoption. Finally, we discuss sequencer incentives and propose a risk-optimized arbitrage strategy.

翻译：近年来，随着新区块链 Layer-1 (L1) 和 Layer-2 (L2) 网络的出现，区块链生态系统已显著扩展。这些区块链通常运行去中心化交易所（DEXes），用于交易原生代币和稳定币等资产。虽然这种多样性丰富了生态系统，但也导致了流动性碎片化，给在多个区块链上提供相同资产的 DEXes 带来了挑战。这种碎片化造成了价格差异，为寻求利润的交易者创造了套利等机会，这属于更广泛的剥削性经济实践范畴，即最大可提取价值（MEV）。尽管 MEV 提取已在单一领域（即单个区块链内）得到广泛研究，但跨链套利作为一种跨域 MEV 形式，由于其非原子性使得执行和检测都变得复杂，因此很少受到关注。在本文中，我们通过首次系统性地研究两种非原子性跨链套利策略：序列无关套利（SIA）和序列相关套利（SDA），揭示了不透明的跨链 MEV 活动。前者涉及跨链的独立、反向交易，而后者依赖于资产桥。我们分析了这些策略在 2023 年 9 月至 2024 年 8 月一年期间在九个区块链上的有效性，识别出 260,808 笔跨链套利交易，其中 32.37% 涉及桥接解决方案。这些套利从总计 465,797,487.98 美元的交易量中产生了至少 9,496,115.28 美元的利润下限。此外，我们研究了跨链套利的安全影响，揭示了套利者之间的中心化、失败交易导致的网络拥堵以及私人内存池采用率的增长。最后，我们讨论了排序器激励并提出了一个风险优化的套利策略。