From: Adamsc@io-online.com (Adamsc)
Date: Wed, 18 Sep 1996 06:11:45 +0800
To: "Jim_Miller@bilbo.suite.com>
Subject: Re: really undetectable crypto
Message-ID: <19960917174627828.AAA205@IO-ONLINE.COM>
MIME-Version: 1.0
Content-Type: text/plain


On Thu, 12 Sep 96 19:26:56 -0700, Jim Miller wrote:


>Most everybody on the list is familiar with the technique of hiding  
>encrypted messages in the LSBs of image files.  Personally, I would not  
>use such a technique because don't I believe it's really undetectable.  I  
>assume, without proof, that the LSBs of images files have statistical  
>properties that are sufficiently different from encrypted data that a  
>clever person could determine whether or not an image file contained an  
>imbedded encrypted message.

Actually, if you use only a few bits - and not, say, bit 15 of *every* pixel -
you can feel secure *IF* you are writing truly encrypted data.  A regular PGP
message has a bunch of header material that most certainly is not
random-looking.  OTOH, if you only write the raw data, then there is no way to
differentiate from the random noise added by any scanner - in most cases, the
last couple bits in each RGB triplet of a truecolor image are random.

# Chris Adams <adamsc@io-online.com> | http://www.io-online.com/adamsc/adamsc.htp
# cadams@acucobol.com | V.M. (619)515-4894
"I have never been able to figure out why anyone would want to play games on
a computer in any case when the whole system is a game.  Word processing,
spreadsheets, telecoms -- it's all a game.  And they pay you to play it."
	-- Duncan Frissell