Steganography, a means by which two or more parties may communicate using "invisible" or "subliminal" communication, and watermarking, a means of hiding copyright data in images, are becoming necessary components of commercial multimedia applications that are subject to illegal use. This is a comprehensive survey of steganography and watermarking and their application to modern communications and multimedia. It helps the reader to understand steganography, the history of this previously neglected element of cryptography, the hurdles of international law on strong cryptographic techniques, and a description of the methods you can use to hide information in modern media. Included in this discussion is an overview of "steganalysis", methods which can be used to break stenographic communication. This resource also includes an introduction to and survey of watermarking methods, and discusses this method's similarities to and differences from steganography. The reader should gain a working knowledge of watermarking's pros and cons, and learn the legal implications of watermarking and copyright issues on the Internet.