Abstract

Cross-chain bridges are crucial mechanisms for facilitating interoperation between different blockchains, allowing the flow of assets and information across various chains. Their pivotal role and the vast value of assets they handle make them highly attractive to attackers. Major security incidents involving cross-chain bridge projects have been occurring frequently, resulting in losses of several billion due to cyber attacks. The diversity of vulnerability exploitation methods by hackers is vast, but not entirely untraceable. There are scarce research outcomes studying cross-chain bridge cyber incidents, and we have conducted a study based on the most recent cross-chain bridge security incidents. We introduce the working principles, components, and architecture of cross-chain bridges, explain the categorization mechanisms of the trust layer in cross-chain bridges, summarize four categories of hacker vulnerability exploitation techniques from real cases, and propose preventative measures for cross-chain bridge security.