From: wcs@anchor.ho.att.com (bill.stewart@pleasantonca.ncr.com +1-510-484-6204)
Date: Thu, 3 Mar 94 17:10:21 PST
To: cypherpunks@toad.com
Subject: Re: Standard for Steganography
Message-ID: <9403040109.AA14831@anchor.ho.att.com>
MIME-Version: 1.0
Content-Type: text/plain


Jef Poskanzer writes:
> The problem is the length field - you've got to have it, and it's
> recognizeable because it begins with a run of 0s. [several hiding approaches.]
Actually, you don't really need it, at least for PGP.  PGP messages keep
track of how much real stuff the message has, and ought to be able to
do the right thing if there's extra stuff at the end; I'd guess that
Stealth-PGP can do the same.  I realize PGP isn't the only thing people
will want to hide, but most things need hiding have enough structure
to them thatpadding wiht garbage at the end is no problem.

On the other hand, if you do have a length field, you do have to
do something reasonable with it, and just putting it at the beginning
makes it difficult to do other stuff with the stego program,
like inserting text bitplanes into a picture....

		Bill