A Systematic Mapping of Quantum Threats and Defenses for Blockchain

Quantum computing poses distinct risks to blockchain security: Shor’s algorithm threatens signatures associated with exposed public keys, while Grover’s algorithm reduces the security margin of hash-based mechanisms. This systematic mapping study examines quantum-resistant blockchain defenses and the evidence supporting their practical use. A total of 387 peer-reviewed primary studies published between 2018 and 2026 were identified through IEEE Xplore, the MDPI journal collection, and citation searching, and classified by contribution type and evidence maturity. The findings show that post-quantum cryptographic constructions dominate the literature (56.1%), followed by quantum-native designs (26.6%) and hybrid migration approaches (13.7%). Despite substantial research on these defenses, only 16.0% of the studies report real-platform laboratory experiments, and 1.3% reach public-testnet evaluation. Hybrid migration studies demonstrate greater progress toward platform-level evaluation than other defense categories, but practical validation remains limited. These findings highlight the gap between proposed quantum-resistant mechanisms and their evaluation under realistic blockchain conditions, emphasizing the need for reproducible system-level testing and migration strategies addressing interoperability, governance, and operational continuity.