Secure Optical Scanning Cryptography based Stereo Image Watermarking using Genetic Algorithm

Watermarking has become an important tool for multimedia object creator or distributor to address the growing concern of multimedia owners. An attempt has been made to develop a complete secure digital stereo image non-blind watermarking system for effective copyright protection. The objective is to embed by watermarking into one stereo image the information needed to recover the other stereo pair (disparity image). A pre-processing stage has been added to the system to make it more robust and to enhance the security of the host image against intruders. The pre-processing stage includes encrypting the embedding medium by a digital simulation of the double random phase encoding based optical scanning cryptography. This encryption technique changes the gray-levels of pixels and hence is more secure than location scrambling algorithms that only change the positions of pixels and not the gray levels. The encryption technique used has also been proved to be secure against statistical, brute-force and key sensibility attacks. Further Genetic Algorithm has been employed for finding optimal values of embedding strength of watermarks. Genetic Algorithm thus frees the user from manually selecting embedding strength of watermarks which is a difficult task. The superiority of the proposed digital stereo image watermarking scheme has been shown by the excellent results achieved for peak signal to noise ratio and normalized correlation.