From: Andrew Loewenstern <andrew_loewenstern@il.us.swissbank.com>
Date: Fri, 6 Oct 95 10:35:53 PDT
To: danisch@ira.uka.de (Hadmut Danisch)
Subject: Re: Graphic encryption
Message-ID: <9510061622.AA02423@ch1d157nwk>
MIME-Version: 1.0
Content-Type: text/plain


>  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.

andrew