Code or messages imbedded in a digital file (containing, for example, an image, audio file, video software, or document). Typically the watermark is undetectable to the standard user, but can be read using the right equipment or algorithms. The watermark serves to identify the source of an image, for security purposes or for detecting copyright infringement. The watermark also can be used for license management, so as to enable licenses to be specific to individual copies of the digital file each bearing a unique watermark.