Quantum Computing meets Blockchain: Threats, Opportunities and a Hybrid Secure Architecture

The convergence of Quantum Computing and Blockchain marks a transformative step in secure distributed systems, offering immense potential and serious security challenges. Quantum algorithms like Shor’s and Grover’s threaten classical cryptographic foundations such as ECC and symmetric key systems, making current blockchains vulnerable. This study explores these vulnerabilities and proposes a hybrid quantum-secure blockchain architecture that integrates post-quantum cryptography such as lattice-based and hash-based algorithms with traditional methods for backward compatibility and efficiency. It also highlights how quantum technologies can enhance blockchain performance through faster consensus and smart contract optimization. The paper concludes that adopting hybrid quantum-resistant mechanisms is vital for ensuring blockchain security, scalability, and resilience in the post-quantum era.