TRAIL: Cross-Shard Validation for Cryptocurrency Byzantine Shard Protection

TL;DR

TRAIL introduces a novel cross-shard validation algorithm for blockchain systems that enhances robustness and efficiency by selecting validator shards based on previous asset holdings, using PBFT-based consensus.

Contribution

It proposes a new cross-shard validation method with a novel shard selection approach and demonstrates its correctness, efficiency, and adaptability to other Byzantine-tolerant consensus algorithms.

Findings

Proves correctness of TRAIL algorithm

Analyzes message complexity and performance

Shows adaptability to various Byzantine consensus protocols

Abstract

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.