An Efficient Dual-Domain Encryption Algorithm for DICOM Medical Images Using a DISCRETE Memristor Chaotic Map

DICOM files store diagnostic pixels together with structured patient attributes that stay linked to the examination in routine hospital use. Most image ciphers leave these tags in plaintext, and encrypting the whole bitstream can break the syntax required by PACS and DICOM viewers. The proposed dual-domain encryption algorithm targets both the sensitive tags (metadata domain) and the pixel data (image domain) of DICOM images, providing holistic protection for medical records by a two-dimensional quadratic memristive sine map (2D-QMSM). Under the selected parameters, both Lyapunov exponents stay positive over a wide interval, and the map supplies the pseudo-random source. Sensitive tag values are serialized, encrypted by AES-GCM with a key and nonce derived from the map, stored in private tags, and cleared from their original fields. Pixel data then pass through multiple rounds of encryption. A coordinate offset and joint plaintext–ciphertext feedback let the same keystream be reused, while a local change still spreads across the image. On several randomly selected 8-bit images from the RSNA Pneumonia Detection Challenge, the cipher-image entropy is 7.9998, adjacent-pixel correlations fall close to zero, and NPCR and UACI stay near 99.609% and 33.464%. Compared with recent medical-image ciphers, the scheme offers similar resistance to statistical and differential attacks and is the only one that also protects sensitive DICOM tags.