Invisible Digital watermarks have been proposed as a method for discouraging illicit copying and distribution of copyright material. While a myriad of algorithms have appeared in recent years, a number of problems remain. In this thesis we develop methods for robustly embedding and extracting 60 to 100 bits of information from an image. These bits can be used to link a buyer and a seller to a given image and consequently be used for copyright protection. When embedding the watermark, a fundamental tradeoff must be made between robustness, visibility and capacity. Robustness refers to the fact that the watermark must survive against attacks from potential pirates. Visibility refers to the requirement that the watermark be imperceptible to the eye. Finally, capacity refers to the amount of information that the watermark must carry.