Digital watermarking has been proposed as a way to identify the source, creator, owner, distributor, or authorized consumer of a document or image. Its objective is to permanently and unalterably mark the image so that the credit or assignment is beyond dispute. In the event of illicit use, the watermark would facilitate the claim of ownership, the receipt of copyright revenues, or successful prosecution.

Watermarking has also been proposed for tracing images that have been illicitly redistributed. In the past, the infeasibility of large-scale photocopying and distribution often limited copyright infringement, but modern digital networks make large-scale dissemination simple and inexpensive. Digital watermarking allows each image to be uniquely marked for every buyer. If that buyer makes an illicit copy, the copy itself identifies the buyer as the source.

Of course, digital watermarking is not the only technology intended to protect intellectual property in digital format. Digital documents are commonly encrypted to make them unviewable without the decryption key. This technique works well for transmission and storage, but once a document is decrypted for viewing or printing, subsequent retransmission or dissemination is not encrypted.

Also see Digital Watermarking by these authors