Steganography Overcomes Cryptography Restrictions

Rainer Mauth

Not only can computer-based steganography be used to embed a watermark in a file to protect intellectual property, new steganographic tools can be used to hide messages in digital images and sounds. This has profound implications for government-certified encryption schemes (e.g., the U.S. Clipper chip initiative and other key-escrow techniques) because with messages hidden in a digital image, anyone can inconspicuously exchange secrets and thus overcome restrictions on cryptography (see "Europe: Who Holds the Keys?," BYTE international edition, April 1996).

There are numerous programs for hiding data in pictures (see http://www.sevenlocks.com/SteganographySoftware.htm ). One of the better-known programs is EzStego by Romana Machado ( http://www.fqa.com/ezstego/ ). It manipulates an image's color palette and puts the binary data of the hidden message into the least-significant bit of the pixels in the image.

Computer-based steganography not only works with pictures or texts but also with digitized speech. A group of information security experts at the Universities of Dresden and Hildesheim in Germany demonstrated last year that it is possible to transmit undetectable data along with speech during an ISDN phone call. Although the demonstration, at the Information Hiding Workshop in Cambridge, U.K., didn't work in real time, the German experts claim that a real-time application can easily be derived.

As Andreas Pfitzmann, professor at the University of Dresden, puts it: "Computer-based steganography proves that restrictions placed on cryptography on any digital medium are nonsense.