Digital Watermarking

Digital watermarking is the act of hiding a message related to a digital signal (i.e. an image, song, video) within the signal itself. It is a concept closely related to steganography, in that they both hide a message inside a digital signal. However, what separates them is their goal. Watermarking tries to hide a message related to the actual content of the digital signal, while in steganography the digital signal has no relation to the message, and it is merely used as a cover to hide its existence. Watermarking has been around for several centuries, in the form of watermarks found initially in plain paper and subsequently in paper bills. However, the field of digital watermarking was only developed during the last 15 years and it is now being used for many different applications. In the following sections I will present some of the most important applications of digital watermarking, explain some key properties that are desirable in a watermarking system, and give an overview of the most common models of watermarking as presented in the book by Ingemar Cox, Matthew Miller, Jeffrey Bloom, Jessica Friedrich and Ton Kalker [1]. These basic models will be further illustrated by the use of example watermarking systems that were developed in Matlab. All images used in this essay, except those used to present the results of the example watermarking systems are taken from this book [1].