Re: Enigma-like cipher: variable rotor stepping




Greg Rose wrote:
In article <1167547137.782040.249240@xxxxxxxxxxxxxxxxxxxxxxxxxxx>,
DarkProtoman <Protoman2050@xxxxxxxxx> wrote:
I'm writing an enigma-like cipher w/five rotors where adjacent rotors
rotate opposite direction of their neighbors and they have variable

I don't think rotating in any particular direction
matters, since it would be exactly equivalent to a
reflected rotor rotating in the same direction.

It does yield the same result, but it's not a useless idea. I actually
implemented both. The rotors can go counter clockwise or clockwise and
they can be mirrored (complete inversion) so that at different point in
time, the behavior of clockwise rotation and counter clockwise rotation
isn't the same for a given rotor.

stepping in which they step a number of times equal to the position of
the character they're on plus one, starting from zero, ie. in FOOD, F's
position would be zero, and the rotors would step once, on O they would
step twice, etc. Keeping w/ the fact that the first rotor would step
after every character, the second rotor would step when the first one
stepped 36 times,etc. How much more security would that give me over a
normal three rotor machine.

I'm not sure that it gives you any extra security
at all. If the rotors stepped irregularly based on
something the attacker didn't already know, that
might be helpfu. (The US M209(?) did this I
believe.)

Indeed. That's where the idea of using another rotor machine to
determine which rotors and how they will evolve comes in. clockwise,
counter clockwise, mirror, swap, etc. I also want to include a
dissapear and reappear feature.

I'm aware of the existence of some
still-classified results against rotor machines. I
wouldn't use one for anything truly important for
that reason.

It depends how they are used, If they are used to generate strong
pseudo random data for one time pad, then the context changes a bit.

Regards
Jean-Francois Michaud

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