An advantage of these methods over those applied to picture images is that, by combining two or three of these to one document, two documents with different watermarks cannot be spatially registered to extract the watermark. Of course, the watermark can be defeated by retyping the text. This counterfeiting scheme could be used to subvert ownership claims because the recovery of the digital signature from a watermarked image requires a comparison with an original. We may illustrate the point simply with graphics. Standard watermarking involves the creation of a watermarked image by encoding a signature into an original image.
Authentication proceeds in two stages.
Identity signifies authenticity of the copy. Basic Watermarking technique. Thus, the technique of establishing legitimate ownership by recovering the signature watermark by comparing a watermarked image with the original image breaks down. While it may be demonstrated that at least one recipient has a counterfeit watermarked copy, it can not be determined who it is. This research suggests that not all watermarking techniques will be useful in resolving ownership disputes in courts of law.