Sign and find images online

While discussing various rights and fair use of images online with Michel V yesterday^*, I wished that the major search engines (aka GYM) would provide us with a way to sign any image (via steganography) then a simple feature allowing to search for signed images published online. This would allow anyone to easily track reuse, fair or not, of their works.

May be it already exists, I don't know. This would be the graphical equivalent of the link: feature in Google (ex. links to this blog home page), and I'm sure it'd be very popular.

Michel pointed out that people could possibly alter the signature if the encode/decode algorythm is know. I don't know this one either, though if we can safely encrypt stuff via public/private keys via open algorithms, this might not be an issue. He also pointed out that different means exist to sign an image, to which I responded that once a prominent actor such as Google comes out with such a feature and a very simple tutorial for webmasters, it would set an industry standard.

(*) we talk notably about the interesting case of images of oneself taken by others and published on Flickr and other online image banks. Questions discussed: in French law, one can object to the publication of any picture of themselves (where recognizable without any doubt) does this promises Flickr and consorts a flurry of legal cases soon? Can I reuse a picture of myself taken by someone else, without their authorization, when it's been published without my consent? Case in point: I've not taken or published any of those images (and I haven't got a clue who "The Shrine of Dr. No" is!)