We present TRAIL: an algorithm that uses a novel consensus procedure to tolerate failed or malicious shards within a blockchain-based cryptocurrency. Our algorithm takes a new approach of selecting validator shards for each transaction from those that previously held the assets being transferred. This approach ensures the algorithm's robustness and efficiency. TRAIL is presented using PBFT for internal shard transaction processing and a modified version of PBFT for external cross-shard validation. We describe TRAIL, prove it correct, analyze its message complexity, and evaluate its performance. We propose various TRAIL optimizations: we describe how it can be adapted to other Byzantine-tolerant consensus algorithms, how a complete system may be built on the basis of it, and how TRAIL can be applied to existing and future sharded blockchains.

翻译：我们提出TRAIL算法，该算法采用新型共识机制来容忍基于区块链的加密货币系统中出现失效或恶意分片。该算法创新性地从交易资产先前所在的分片中选取验证分片，从而确保算法的鲁棒性与高效性。TRAIL采用PBFT协议处理分片内部交易，并基于改进版PBFT实现跨分片验证。本文详细描述TRAIL算法、证明其正确性、分析消息复杂度并评估其性能。我们提出多种TRAIL优化方案：阐述如何将其适配至其他拜占庭容错共识算法、如何基于该算法构建完整系统，以及如何将其应用于现有及未来的分片区块链架构。