Random-dot stereograms

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5 total messages Started by Richard Tobin Mon, 06 Apr 1992 18:55

#555

Author: Richard Tobin
Date: Mon, 06 Apr 1992 18:55

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It occurs to me that random-dot stereograms could be used for
transmitting small amounts of information securely.  The recipient
would be provided in advance with one half of the stereogram, and the
other half would be constructed when needed.  This is equivalent to a
one-time pad, with the advantages that

 (a) it can be decoded with no equipment in a few seconds
 (b) it can easily be used for transmitting diagrams as well as text.

Has this ever been done?

[A random-dot stereogram consists of two images of random dots.  The
two are identical except that some areas of dots are displaced slightly
in one of the images (and the resulting gap filled with more random dots).
If one image is viewed with each eye (which can be done by crossing your
eyes) the displaced areas are perceived as being at different distances.]

-- Richard
-- 
Richard Tobin,
AI Applications Institute,                                R.Tobin@ed.ac.uk
Edinburgh University.

Re: Random-dot stereograms

#556

Author: The Land of Confusion
Date: Tue, 07 Apr 1992 16:28

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In article <6568@skye.ed.ac.uk>, richard@aiai.ed.ac.uk (Richard Tobin) writes:
> It occurs to me that random-dot stereograms could be used for
> transmitting small amounts of information securely.  The recipient
> would be provided in advance with one half of the stereogram, and the
> other half would be constructed when needed.  

As the information in a random dot stereogram is stored in the disparities
between corresponding dots in the pair of images, isn't it necessary to
have the plain text in advance of constructing *both* images? This seems
to indicate that the `key' half is not in fact independent of the information 
to be securely transmitted and could therefore not be provided `in advance'.

--
graham

 \/                                                                          \/
 /\                   Motto withheld pending investigation                   /\
 \/                                                                          \/

Re: Random-dot stereograms

#559

Author: Sean Casey
Date: Tue, 07 Apr 1992 22:12

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I find this interesting. If you represent text photographically, i.e.
your ciphertext is an image, does that make attacks harder? It seems
on first thought that traditional techniques would not work, and image
recognition algorithms would need to be used.

Very interesting...

Sean
-- 
                  |``Wind, waves, etc. are breakdowns in the face of the
Sean Casey        | commitment to getting from here to there. But they are the
sean@s.ms.uky.edu | conditions for sailing -- not something to be gotten rid
U of KY, Lexington| of, but something to be danced with.''

Re: Random-dot stereograms

#562

Author: Marshall G. Flax
Date: Wed, 08 Apr 1992 03:26

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In article <1992Apr7.172817@sees.bangor.ac.uk> graham@sees.bangor.ac.uk (The Land of Confusion) writes:
>As the information in a random dot stereogram is stored in the disparities
>between corresponding dots in the pair of images, isn't it necessary to
>have the plain text in advance of constructing *both* images? 

Nope.  Here a simple algorithm.  Suppose the left half has already been
sent.  Then take a copy of the left image, cut out the plaintext in
bubble letters of the like, slide it over, and fill in the holes with
more random dots.  Now you have the right side image.  It's not
difficult at all.  It's just a lot of info to transmit over secure
lines!!!

marshall
-- 
+++++++++++++++++++++++++++f+++++n+++++o+++++r+++++d+++++++++++++++++++++++++++
++++++++++++++  40 Linden Lane|Princeton, NJ 08540|609-921-0962  ++++++++++++++
+++++  Copyright 1992, Marshall Gene Flax <mgflax@phoenix.Princeton.EDU>  +++++
+ c/o Jack Gelfand|Psychology Dept|Princeton University,NJ 08544|609-258-6739 +

Re: Random-dot stereograms

#567

Author: Gurupartap Davis
Date: Wed, 08 Apr 1992 23:54

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In article <1992Apr8.032639.28004@Princeton.EDU> mgflax@phoenix.Princeton.EDU (Marshall G. Flax) writes:
>In article <1992Apr7.172817@sees.bangor.ac.uk> graham@sees.bangor.ac.uk (The Land of Confusion) writes:
>>As the information in a random dot stereogram is stored in the disparities
>>between corresponding dots in the pair of images, isn't it necessary to
>>have the plain text in advance of constructing *both* images? 
>
>Nope.  Here a simple algorithm.  Suppose the left half has already been
>sent.  Then take a copy of the left image, cut out the plaintext in
>bubble letters of the like, slide it over, and fill in the holes with
>more random dots.  Now you have the right side image.  It's not

I think I see how this works, but how do you fit the two images together?
Do you just place them side by side?  If so, then a particularly wide picture
would require some serious eye-focusing exercise.  In that case, do you
make the picture up of alternating left and right-eye views?  How excactly
is this accomplished?

--Partap

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