On the reliability of detecting electronic watermarks in digital images

A watermark is a perceptually unobstructive mark embedded in an image, audio or video clip or other multimedia asset. A watermark can carry additional information, for instance about the source and copyright status of a document or its intended recipient, its rights and restrictions. We analyse the reliability of detecting such watermarks, modeling it as a detection problem where the original content acts as noise or interference. Probabilities of incorrect detections are expressed in terms of the watermark-to-image power ratio, showing a significant similarity in the problem of detecting watermarks and that of receiving weak spread-spectrum signals over a radio channel with strong interference. Theoretical results are verified by experiments.