Implementation & Performance Analysis of Various Digital Watermarking Techniques

The digitization of the information has revolutionized the daily lives of the peoples in this world. The many advantages of digital information have also generated new challenges and new opportunities for innovation. This thesis discusses the issues regarding data hiding and its application to multimedia security and communication, addressing both theoretical and practical aspects, and tackling both design and attack problems. In the fundamental part, it has been identified a few key elements of data hiding through a layered structure. Data hiding is modeled as a communication problem where the embedded data is the signal to be transmitted. Various embedding mechanisms target different robustness-capacity tradeoffs. The tradeoff for different major categories of embedding mechanisms has been done. In addition, it has been found that the unevenly distributed embedding capacity brings difficulty in data hiding. A comprehensive study has been done to solve this problem, addressing the considerations for choosing constant or variable embedding rate and enhancing the performance for each case i.e. using smaller watermark or increasing processing gain at the cost of degradation in the image quality. Various, data hiding algorithms in spatial domain, frequency domain, fractal domain and wavelet domain for binary images, grayscale images has been implemented. These algorithms are covering applications such as annotation, tamper detection, copy/access control, fingerprinting, and ownership protection. Data hiding can also be used in video communication to convey side information for additional functionalities or better performance. In the attack part, discussion on a number of attacks like cropping, addition of noise, JPEG compression and other geometrical attacks and countermeasures for data hiding systems has been done. The investigation begins with four specific types of watermarking schemes, in which full knowledge of the watermarking algorithms is available. The attack problems have been studied for digital images under a unique competitive environment, using blind and non blind watermarking algorithms of digital watermarking. On basis of overall discussion it can be concluded that watermarking in dual domain is considered the best among the discussed algorithms.