Quantum-inspired post-quantum secure DCT watermarking for tamper detection and localization in medical images

As medical imaging becomes increasingly central to telemedicine and electronic health records; robust integrity verification is required to preserve diagnostic quality while enabling precise tamper detection. Existing quantum image watermarking methods lack post-quantum key security and deliberate fragility. This paper proposes a quantum-inspired watermarking framework for medical images with post-quantum key security and deliberate fragility based on entangled DCT coefficients. Watermarks are carried by collective coefficient sums, making any alteration detectable. Post-quantum security is ensured through SHA3-256 key derivation. Experiments on three medical datasets (ChestX-ray14, BraTS, OCTID) show excellent imperceptibility (PSNR 44.2 dB, SSIM >0.98), high tamper sensitivity (BER >30%), and precise localization (accuracy >80%). Unlike prior methods, the framework integrates post-quantum security, deliberate fragility, and tamper localization. Furthermore, a lightweight Random Forest classifier is trained on global and block-wise BER statistics to automatically distinguish intact images from those subjected to benign processing or malicious tampering, enhancing the system's practical utility as an AI-assisted integrity verification tool for medical images in future quantum-threat environments.