[Cryptography] Brainstorming for encrypted text messaging ideas...with a twist

[Ray Dillinger]

On 06/22/2017 03:52 AM, Arnold Reinhold wrote:

> ..... The front side had 100 sets of complete mono-spaced, ordered alphabets (ABCDEFGHIJKLMNOPQRSTUVWXYZ). The back had 100 randomly permuted alphabets, one behind each ordered alphabet on the front.... To encode with such a sheet, one placed it on a sheet of carbon paper with the carbon side up. The user circles  one letter of plain text in each alphabet. After the letters in the message were circled, one flipped the page over and read off the ciphertext from the randomized alphabets. 
> 
> A naive way to use the ORION system would be to follow the encoding procedure above and then take a picture of the reverse side and send it to the recipient.... The problem, of course, it that the position of the circled letter
in each line of the ciphertext side reveals the plaintext letter.  I
propose to overcome this as follows. Instead of ordered alphabets on the
 front side, have randomly scrambled alphabets.

I don't understand why to not just use the original format for the Orion
sheets. One places the carbon paper directly on the desk, carbon side
up.  Then the Orion sheet, with the ordered alphabets down, upon the
carbon.  Then you go down (or across) the sheet, circling the letters of
the plaintext in the permuted alphabets.

Turn the sheet over and what is now visible is the ordered alphabets,
with apparently-random letters circled in carbon impression.  If the
plaintext side is in fact not visible through the paper, then a pic of
this sheet can be sent directly.  If the carbon paper is dusty on the
non-carbon side, or your stylus leaves an impression on the wood and a
"side channel" is made on the surface of your desk, the side channel
only reveals the ciphertext again.

Ultimately the encryption effort is no easier (Alice still has to find
the letters in a randomly-permuted alphabet) but there seems to be no
cryptographic logic requiring permuted alphabets on both sides.  The
location of the ciphertext letter in a non-permuted alphabet reveals
nothing about the plaintext letter.

As to trusting that the printing on the plaintext side is not in fact
visible through the paper, one *could* worry about the paper and the
optics and the light and the cameras.  I would prefer to unfold the
paper at the center crease, tear along the perforated line, and use it
to make the water in a blender just a bit less clear than it was before.


				Bear

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