Lossless and Robust Digital Watermarking Scheme for Retinal Images

Medical images are watermarked with patient details to maintain patient's privacy and to address other security issues during transmission and process of storage in large distributed databases. Conventional watermarking does not suit the different requirements of medical imaging as it brings in some modifications which is not at all acceptable in case of medical images. This paper presents a Wavelet transform-Singular Value Decomposition based robust zero-watermarking technique for medical images to address the privacy and security issues. Unlike conventional watermarking, the proposed method conserves the reliability of the cover image without bringing any artifacts and without any change in the critical information contained in the medical image. The performance of the scheme is assessed with tele-ophthalmological images. The simulation results reveal the robustness of the proposed technique against various image processing attacks and indicate its suitability for safe exchange of medical images among remote medical practitioners.