From: patrick@Verity.COM (Patrick Horgan)
Date: Sun, 8 Oct 95 17:32:45 PDT
To: danisch@ira.uka.de
Subject: Re: Graphic encryption
Message-ID: <9510090028.AA02204@cantina.verity.com>
MIME-Version: 1.0
Content-Type: text/plain


> From: Andrew Loewenstern <andrew_loewenstern@il.us.swissbank.com>
> 
> >  Is there anything particular in graphic encryption? I usually
> >  encrypt graphics and document images as regular files with regular
> >  encryption...
> 
> I believe graphic encryption outputs a valid image file that is apparently  
> white noise until you perform the decryption transformation on it.  An  
> obvious way to do this with a non-lossy file format is to encrypt pixel vales  
> with a stream cipher.  Another way to make the image unviewable would be to  
> shuffle the pixels or rasters with a PRNG.
> 

I thought it was the ideas presented in Dr Dobbs last year of encoding other
information in a graphic image so that the image still looked the same, but
the other information could be extracted...i.e. using the image as a covert
channel.  Does anyone know what they're really talking about?

Patrick
   _______________________________________________________________________
  /  These opinions are mine, and not Verity's (except by coincidence;).  \
 |                                                       (\                |
 |  Patrick J. Horgan         Verity Inc.                 \\    Have       |
 |  patrick@verity.com        1550 Plymouth Street         \\  _ Sword     | 
 |  Phone : (415)960-7600     Mountain View                 \\/    Will    | 
 |  FAX   : (415)960-7750     California 94303             _/\\     Travel | 
  \___________________________________________________________\)__________/