[Cryptography] how to detect breakage -- lures etc.??

[Arnold Reinhold]

On Sat, 04 Jan 2020 16:19 Ray Dillinger wrote:
> ...This is about the difference between
> uniform movement and movement complex enough that you hope the enemy
> never figures it out. Uniform movement, natch, the enemy has already
> figured out.  But it doesn't present opportunities to use partial
> information the way complex movement does, so having figured it out
> doesn't do the enemy any good.  IOW, you don't need movement complexity
> to hide behind if there is nothing to be gained from knowing the
> movement pattern.
> 
> The fact that with same-size rotors some of them must move only
> "sometimes" in order to get a decent period, means the opponent sees
> the results of different sets of the rotors moving.  From the
> differences in effect, the opponent can isolate the effects of one
> rotor or one subset of rotors, then use that connection matrix to
> subtract its effect and isolate another, etc.... 

> … FWIW, I had envisioned a machine in which part of the wiring between
> rotors would be determined by the key, for the reason of making the
> sequence of cipher alphabets for the whole cycle vary by key. …

If I understand your concept correctly, you are proposing a cipher based on a pseudo-random sequence generator made up of rotors of different periods with incommensurate lengths to produce a very long overall period, where the connections between the individual rotors can be varied according to a key so as to produces a very large set of different sequences. It’s my understanding that is pretty much what the NSA ended up doing in the 1950s, except they used binary electronic shift registers with feedback instead of alphabetic rotors. Your rotor idea may well have worked, but major military communications circuits were migrating to radio and landline teletype from Morse code, so binary made sense and electronics were the future. 

Transistors were not ready for prime time in the early '50s, so NSA used bi-stable transformer logic, along with vacuum tubes, in its first systems, e.g. the KW-26.( https://www.nsa.gov/Portals/70/documents/about/cryptologic-heritage/historical-figures-publications/publications/technology/tsec_kw26.pdf?ver=2019-08-07-124409-367 ) I’m not aware of the actual algorithms NSA used being publicly available (and I have no inside knowledge), but there has been cryptanalytic attacks on commercial shift register ciphers that might suggest things to avoid in your rotor design. 

Arnold Reinhold