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Abstract

Blockchain interoperability enables independent blockchain systems to communicate and exchange assets across heterogeneous networks. A major weakness limiting its effectiveness is the lack of comprehensive security mechanisms. Attacks have already caused hundreds of millions in asset losses, demonstrating the severity of this threat. This paper identifies and counters all known attacks and vulnerabilities facing interoperable blockchain systems. We classify threats into five categories: (1) core blockchain attacks, (2) network attacks, (3) interoperability-specific attacks, (4) social engineering, and (5) code vulnerabilities particularly in smart contracts. For each threat, we identify effective countermeasures. By cataloging these threats and their solutions, we provide a foundation for designing secure blockchain interoperability solutions.