Information hiding in digital images: Watermarking and steganography

Information hiding in multimedia data has drawn a lot of attention in recent years. A message is hidden in digital images, video and audio in an imperceptible manner so as not to interfere with the normal usage of these host media files while its existence can be helpful for some interesting applications. The hidden information related to content protection is usually termed Digital Watermark. The recent proliferation of the information-hiding research mostly comes from the development of digital watermarking techniques to meet the pressing need of content protection. The other interesting application is to transmit a large volume of data covertly in a multimedia file via information hiding. The objective in this application is to conceal the very existence of the hidden information using the innocuous multimedia data as a camouflage. Data hiding under this scenario is often termed Steganography, which literally means “covered writing.”; In this research, we focus on information hiding in digital images. The dissertation consists of two major parts. In the first part, we investigate information hiding in the state-of-the-art still image codec, JPEG-2000. A joint compression/watermarking scheme is proposed for the copyright protection purpose. Next, we consider steganography in JPEG-2000. Algorithms are developed to ensure that a high volume of data can be hidden reliably in JPEG-2000 compressed images.; In the second part, we aim at solving a very challenging problem in digital image watermarking, i.e., synchronized detection under geometrical modifications. In order to derive a robust watermarking scheme resilient to affine transformations, we propose to embed a structural grid signal into digital images for synchronized watermark detection. A spatial-frequency composite watermarking scheme is designed so that the watermark can survive attacks such as rotation, scaling and cropping; etc. A perceptual watermarking scheme using block-based DCT methodology is also developed. It turns out that grid embedding/detection is of great help in developing generalized block-based watermarking as well. Finally, the dissertation ends with some concluding remarks and some future research topics as an extension of our current research.