Invertible and Fragile Watermarking for Medical Images Using Residue Number System and Chaos

—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 watermark being fragile using cyclic redundancy check (CRC) is embedded chaotically to some of the pixels and the rest of the pixels are changed into residues. By adding a chaotic watermark, the watermarked pixel becomes twelve bits and the residues also became twelve bits (after applying CRC) which makes the medical image secure by confusing the attacker about the location of watermark. The complexity of proposed system is very low to make it possible for real-time medical imaging. Furthermore, the proposed scheme is based on blind technique.