Tamper Localisation Using Quantum Fourier Transform Signatures for Medical Image Authentication
Kumar Sekhar Roy, Shweta Singh, Ruhul Amin Hazarika, Sk Mahmudul Hassan, Himanshu Ranjan Das · IET Quantum Communication · 2025
ABSTRACT Medical image integrity is critical as telemedicine, cloud PACS and AI‐assisted diagnostics become routine. We present a tamper localisation framework that embeds authentication signatures in the phase domain of blockwise quantum Fourier transform (QFT) coefficients. The watermark is phase‐only, energy preserving and keyed through sparse midband supports with paired phase differences; a light cross‐block coupling imposes spatial consistency so that localised edits produce coherent high‐contrast residuals confined to manipulated regions after inverse QFT. Because magnitudes remain unaltered, benign photometric variations are naturally attenuated, improving specificity under common acquisition and storage pipelines. The verifier computes circular phase residuals and applies an adaptive threshold to generate blockwise tamper maps, which are refined to pixel resolution. Across standard distortions (JPEG recompression, Gaussian noise and blur) and localised forgeries (copy–move, inpainting and contrast edits), the scheme maintains diagnostic fidelity (typical PSNR 40 dB, SSIM 0.98) while delivering precise spatially resolved detection. The design is deterministic and reproducible via seeded keys, integrates with DICOM workflows and is amenable to future quantum hardware realisation. This work contributes a quantum‐ready, imperceptible and localisation‐oriented approach to medical image authentication suitable for deployment in modern healthcare systems. The proposed QFT phase–only watermark achieves imperceptibility (global PSNR dB; SSIM ) and detects localised tampering (ROC AUC under class imbalance).