Reversible and Robust Watermarking using Residue Number System and Product Codes

Reversible watermarking is a process in which the watermark is embedded in such a way that when the watermarked image passes through the authentication process, the original image is also recovered exactly along with watermark. Restoring the original image is important for the applications such as medical, military and law-enforcement etc. Reversible fragile watermarking scheme is presented by introducing the Residue Number System (RNS). One redundant bit is added as a watermark to some of the pixels and rest is changed into residues. By adding an extra bit, the watermarked pixel becomes nine bits and the residues became nine bits which makes the medical image secure by confusing the attacker that where the watermark is embedded. Robustness in digital watermarking is required especially when communication links are involved in image transmission. In this paper product codes are proposed since their structural properties are compatible with the images. For decoding of these codes modified iterative decoding algorithm is used which is a low complexity suboptimum algorithm. Results show that proposed scheme performs well against noise attacks.