Enhancing E-Security by Inserting a Watermark Using the Combination of Genetic Algorithm and Tabu Search

This paper presents a new method for determining the middle band of discrete cosine transform based on the combination of genetic algorithm and tabu search. As embedded watermark is visible in low frequencies, and not resistant against attacks in high frequencies, the most suitable band for embedding is the middle band. In the Fourier domain, it can be determined by some filters but such a method does not exist in the discrete cosine domain. In discrete cosine transform the arrangement of frequency components does not have the orderliness of the Fourier transform itself, so, it is tried to find the middle band of image by Fourier transform and then find the exact location of the  middle band of discrete cosine transform by genetic algorithm and tabu search. In this method, we minimize the difference between the image that is obtained by applying the middle band of discrete cosine transform mask and the image obtained by the Fourier transform mask. Also, the proposed method can be used for low and high band of discrete cosine transform masks. The implementation and tests for low, middle and high bands resulted in 0.0062, 0.0149 and 0.0061 averages errors, respectively. These results for the test images are satisfactory.