Cross-Chain Vulnerabilities in the Quantum Era: A Threat Analysis to Blockchain Interoperability

As blockchain technologies continue to evolve, interoperability between different blockchain networks has become a critical aspect for enabling seamless communication and data exchange across decentralized platforms. However, the advent of cryptographically relevant quantum computers poses a significant threat to the security foundations that underpin these cross-chain interactions. This paper presents an in-depth review of the vulnerabilities faced by blockchain interoperability mechanisms during the quantum era, specifically by the potential quantum computing threat against widely used cryptographic primitives, namely elliptic curve cryptography and hash functions. It delves into how quantum attacks, specifically Shor's and Grover's algorithms, would compromise the integrity of cross-chain protocols and thus disrupt the security of decentralized exchanges, smart contracts, and atomic swaps. We also review current research activities and suggest possible mitigation strategies, such as post-quantum cryptographic solutions, to ensure the future of blockchain interoperability. This paper is meant to emphasize the need for the blockchain community to prepare for quantum threats and ensure the long-term viability and security of decentralized systems across multiple chains.