Xscope: Hunting for Cross-Chain Bridge Attacks

TL;DR

Xscope is a novel automated tool designed to identify security vulnerabilities and detect attacks in cross-chain bridges, addressing a critical gap in blockchain security research.

Contribution

The paper introduces Xscope, the first automated tool for security analysis of cross-chain bridges, and documents new classes of security bugs and patterns.

Findings

Xscope detects all known cross-chain bridge attacks.

Xscope uncovers previously unreported suspicious attacks.

The study highlights significant security vulnerabilities in popular bridges.

Abstract

Cross-Chain bridges have become the most popular solution to support asset interoperability between heterogeneous blockchains. However, while providing efficient and flexible cross-chain asset transfer, the complex workflow involving both on-chain smart contracts and off-chain programs causes emerging security issues. In the past year, there have been more than ten severe attacks against cross-chain bridges, causing billions of loss. With few studies focusing on the security of cross-chain bridges, the community still lacks the knowledge and tools to mitigate this significant threat. To bridge the gap, we conduct the first study on the security of cross-chain bridges. We document three new classes of security bugs and propose a set of security properties and patterns to characterize them. Based on those patterns, we design Xscope, an automatic tool to find security violations in cross-chain bridges and detect real-world attacks. We evaluate Xscope on four popular cross-chain bridges. It successfully detects all known attacks and finds suspicious attacks unreported before. A video of Xscope is available at https://youtu.be/vMRO_qOqtXY.