Imperceptible watermarking of digital images,
audio and video has been proposed as an efficient way to protect the copyright property of
the legal owners or providers. A particular watermark belongs exclusively to one owner who
is the only person that can proceed to a trustworthy detection of its personal watermark
and thus prove the ownership of the host signal.
A lot of research has been devoted in recent
years to watermark embedding and detection. The fundamental question how to generate
cryptograpically secure watermarks, however, has not at all received as much attention. It
is the purpose of this paper to provide a computationally efficient and elegant method for
generating key-dependent watermarks. We use discrete versions of chaotic Kolmogorov flows
to map a pulicly known corporate logo via a private watermark key onto a watermark which
depends on the key in a very complex, cryptographically strong manner. Mixing this
(comparatively small) logo over the entire image size defines the positions where to
modify the image that is to be watermarked and where to leave values unchanged.