Robust and Secure Multiple Watermarking Technique for Application in Tele-Ophthalmology

Abstract

This chapter presents a new secure multiple text and image watermarking scheme on cover eye image using fusion of discrete wavelet transforms (DWT) and singular value decomposition (SVD) for tele-ophthalmology. Secure Hash Algorithm (SHA-512) is used for generating hash corresponding to iris part of the cover digital eye image and this unique hash parameter is used for enhancing the security feature of the proposed watermarking technique. Simultaneous embedding of four different watermarks (i.e. Signature, index, caption and reference watermark) in form of image and text to achieve the various advantages of multiple watermarking such as enhance the security, reduce the bandwidth and storage requirements, protection against tempering and hidden watermark acting as a keywords for efficient archiving and data retrieval from querying mechanisms in the area of medical. The suggested technique initially divides the digital eye image into region of interest (ROI) containing iris and non-region of interest (NROI) part where the text and image watermarks are embedded into the NROI part of the DWT cover image. The selection of DWT decomposition level for embedding the text and image watermarks depends on size, different characteristics and robustness requirements of medical watermark. The performance in terms of normalized correlation (NC) and bit error rate (BER) of the developed scheme is evaluated and analyzed against known signal processing attacks including ‘Checkmark’ attacks. The method is found to be robust against all the considered attacks. The proposed multilevel watermarking method correctly extracts the embedded watermarks without error and is robust against the all considered attacks without significant degradation of the medical image quality of the watermarked image. Therefore the proposed method may find potential application in secure and compact medical data transmission for tele-ophthalmology applications.