Re: Call for stego ideas

From: Arthur J. O'Dwyer (ajo_at_nospam.andrew.cmu.edu)
Date: 07/12/04 

Date: Mon, 12 Jul 2004 17:22:39 -0400 (EDT)

On Mon, 12 Jul 2004, John Bailey wrote:
>
> >John Bailey <john_bailey@rochester.rr.com> says...
> >>software is readily available and not suspicious. Random dot
> >>stereograms consist of vertical stripes of random dots in which the
> >>position of certain areas are displaced relative to corresponding
> >>areas in adjacent stripes. Converting purely random dots into random
> >>dots modulated by a message can be accomplished...
>
> I have placed double message stereograms at:
> http://home.rochester.rr.com/jbxroads/interests/rec.puzzles/images/
> Both dynamite.gif and etimanyd.gif can be read as a stereogram.
> If the two images are superimposed and added, as for example, with
> overlayed transparencies, a different message is seen.
>
> Note that dynamite.gif, when viewed as a stereogram, shows some
> artifacts which can almost be read. The other stereogram,
> etimanyd.gif, which was the original has no artifacts. I believe that
> it is possible to eliminate all leakage of this sort, however it is
> something still under study.

  Yes, this would definitely fall on my list of "amazingly nifty
results in recreational crypto" if it were really possible to eliminate
the artifacts in the first image. As it stands, this method fails
to be real stego, since the presence of the artifacts shows that a
secret message has been hidden. (It's also bad IMHO that the two
stereograms have exactly the same bits in other places; this ought
to be something built on top of the method using

  X. .X
  .X X.

blocks, oughtn't it? :) It would be double-nifty if the two stereograms
showed *different* 3D images, and double-stego-secure if there were a
*single* stereogram image whose left and right halves superimposed
displayed the secret message, rather than two different stereogram
images.

  Unfortunately, I myself know next to nothing about random dot
stereograms. Definitely post if you figure out how to remove the
artifacts, please!

-Arthur