digital watermarking

Computing techniques for inseparably embedding unobtrusive marks or labels as bits in digital data -- text, graphics, images, video, or audio -- and for detecting or extracting the marks later.

Tutorial: A "digital watermark", i.e., the set of embedded bits, is sometimes hidden, usually imperceptible, and always intended to be unobtrusive. Depending on the particular technique that is used, digital watermarking can assist in proving ownership, controlling duplication, tracing distribution, ensuring data integrity, and performing other functions to protect intellectual property rights. [ACM]