posted on Oct, 17 2004 @ 08:14 AM
There is something called "watermark" from a company called Digimarc.
Photoshop and Paint Shop Pro use this, so you can put an invisible signature in a picture, and anyone with compatible software can search the picture
for a "watermark". If it finds one, it shows the information that was hidden in the picture, usually the copyright owner and such.
There are also free programs that let you hide information inside pictures, but this method and the Digimarc method usually do not survive if you
change the picture, like resizing, blurring, etc., but if when the Digimarc was applied it was made more resistant, this can survive some editing of
the image.