Steganography is hiding a message (typically text) in another message (typically an image file).

This way, you not only hide the message itself, but also the fact that you are sending this message.

Watermarking. certifications.

* http://outguess.org/
* http://www.stack.nl/~galactus/remailers/index-stego.html
* http://petitcolas.net/fabien/steganography/
* http://members.tripod.com/steganography/stego/info.html (BrokenLink 26Feb04)