The proliferation of blockchain-backed cryptocurrencies has sparked the need for cross-chain exchanges of diverse digital assets. Unfortunately, current exchanges suffer from high on-chain verification costs, weak threat models of central trusted parties, or synchronous requirements, making them impractical for currency trading applications. In this paper, we present MERCURY, a practical cryptocurrency exchange that is trust-minimized and efficient without online-client requirements. MERCURY leverages Trusted Execution Environments (TEEs) to shield participants from malicious behaviors, eliminating the reliance on trusted participants and making on-chain verification efficient. Despite the simple idea, building a practical TEE-assisted cross-chain exchange is challenging due to the security and unavailability issues of TEEs. MERCURY tackles the unavailability problem of TEEs by implementing an efficient challenge-response mechanism executed on smart contracts. Furthermore, MERCURY utilizes a lightweight transaction verification mechanism and adopts multiple optimizations to reduce on-chain costs. Comparative evaluations with XClaim, ZK-bridge, and Tesseract demonstrate that MERCURY significantly reduces on-chain costs by approximately 67.87%, 45.01%, and 47.70%, respectively.

翻译：区块链支持的加密货币的激增引发了对多样化数字资产进行跨链交易的需求。遗憾的是，现有交易系统存在链上验证成本高、中心化可信方威胁模型弱或需要同步要求等问题，使其难以适用于实际的货币交易应用。本文提出MERCURY，一种无需在线客户端要求、信任最小化且高效的实用加密货币交易系统。MERCURY利用可信执行环境（TEE）保护参与者免受恶意行为侵害，消除了对可信参与方的依赖，并使链上验证高效化。尽管原理简单，但由于TEE的安全性和可用性问题，构建实用的TEE辅助跨链交易系统仍面临挑战。MERCURY通过在智能合约上执行高效挑战-响应机制，解决了TEE的可用性问题。此外，MERCURY采用轻量级交易验证机制，并实施多项优化以降低链上成本。与XClaim、ZK-bridge和Tesseract的对比评估表明，MERCURY分别显著降低了约67.87%、45.01%和47.70%的链上成本。