From: Seth Morris <Seth.Morris@lambada.oit.unc.edu>
Date: Mon, 15 Mar 93 18:27:18 PST
To: cypherpunks@toad.com
Subject: HIDE (Fnord): Targa-24/YUV/D-xxx and headers
Message-ID: <9303132047.AA05640@lambada.oit.unc.edu>
MIME-Version: 1.0
Content-Type: text



 W.r.t. the steganography issue and image files (although I think sound
files are probably more useful), Targa-24 images are RGB bytes (triples for
each pixel, bottom-left to top-right), and seem appropriate for hiding a 
msg. They are also widely supported for conversion and function as a nice
"device independant" image format (The Stone Soup Group's PicLab does a
good job on them, IMHO).
 Does anyone know anything about YUV format? Also, DYUV or some other delta
compressed format seems good. If a pixel changes by one more or one less
than it "should" the image simply looks like a mediocre scan.
 Hmmm..... FLI is a delta format... is it appropriate?

 So... can someone whip up a utility to strip the PGP header and then
perfoem some simple filtering (^= with some magic numbers, perhaps, or
with some function of the preceeding bytes? Can this eventually help
recover a better image, if that could ever be important? I don't think so)
and tack on a valid Targa or other header (or correct any headers on 
images we've slid into).

 I just started a new job and am swamped, or I'd have written first and
posted later ;-) .

	Seth morris <seth.morris@laUNChpad.unc.edu>