[Cryptography] cryptography Digest, Vol 50, Issue 16

[Grant Schultz]

Bear wrote:
> So....  This might actually be mechanically possible, if complex. I
> imagine a device with a set of message wheels (20 alphabetic rotors?)
> under a narrow window so you could read one row. Visible on the opposite
> side through a different window but probably on the same axle, would be
> a set of key rotors (another 20 alphabetic rotors?).  Each rotor would
> be settable with a thumb wheel, and there'd be a winder and a counter on
> one end.
>
>
Thought about using paper tape (M. K. Shen), but (as with printing 
visual crypto transparencies) the tape would not be easy to punch. I 
don't have access to any vintage computer equipment either.

The pairs of 20 rotors, with one set showing from each side of the unit 
sounds promising, though.  (Might need some 3-D printer time...)  I had 
even considered that  for use with the one-time pad, where one set of 
wheels would be for the key, and one for plain/ciphertext.  You would 
reset the keywheels to "AAAA...", then enter the plaintext on the 
plain/cipher wheels.  Moving the plain/cipher wheels would _not_ cause 
the keywheels to move.  Then you would move the keywheels forward, based 
on the one-time key. Moving the key wheels _would_ step the plain/cipher 
wheels by the same amount.  This would add the key characters to the 
plaintext characters (modulo 26), leaving the ciphertext on those 
wheels. (The keywheel window could have a cover to prevent accidentally 
flashing it to the camera on the phone.)

The internal gearing would not be as complex, and would only connect the 
cipher/plaintext and key rotors of one pair at a time.  Your auto-keyed 
cipher idea would require some mechanical engineering that is beyond my 
capabilities.

Grant