Future Digital Identity Management with Quantum Secure Blockchain

Quantum computing poses a significant threat to the cryptographic foundations of traditional blockchain-based identity management systems and could compromise the security and privacy of digital identities. This survey critically evaluates the emerging landscape of quantum-secure blockchain solutions for digital identity management. We analyze the technical underpinnings, strengths, weaknesses, and potential applications of post-quantum, hybrid-quantum, and fully quantum blockchain approaches. Post-quantum blockchains leveraging quantum-resistant cryptographic algorithms such as lattice-based (e.g., CRYSTALS-Dilithium), hash-based (e.g., SPHINCS+), code-based (e.g., McEliece), and multivariate schemes offer near-term feasibility by integrating into existing infrastructures but face performance trade-offs and potential long-term risks. Hybrid quantum blockchains combining classical blockchain mechanisms with quantum technologies enable enhanced security and gradual transitions but require complex integration efforts and specialized infrastructure. Fully quantum blockchains utilizing quantum entanglement and quantum key distribution (QKD) promise unmatched theoretical security but remain constrained by the immaturity of quantum hardware and algorithms. To provide actionable insights, this paper introduces the Quantum Blockchain Digital Identity Framework (QBDIF) and examines practical implementations such as the Quantum Resistant Ledger (QRL), highlighting critical trade-offs between security, scalability, and practicality in quantum-secure identity management. Our survey emphasizes the need for future research in scalable and efficient quantum-resistant cryptographic algorithms, hybrid consensus mechanisms, and innovative applications of quantum machine learning for blockchain-based identity systems.