[continued from previous message]   
      
   eliminationg redundancy (not doubling info about initial   
   position) would even more effective (IIUC Germans did something   
   like this in 1943).   
      
   Looking at machines using similar principle, one probably should   
   make rotor movement much less regular than it was in Enigma.   
   In particular in Enigma second and third rotor moved rarely.  But   
   already Enigma was mechanically challenging compared to   
   earlier attempts at similar machines.   
      
   AFAICS Enigma is weaker than more modern system due to property that   
   each character of encrypted message depends only on machine settings   
   and corresponding character in plain text.  Moreover, switchboard   
   is applied "from outside" in a way that leaks information allowing   
   determining rotor positions independently from switchboard.   
      
   >   Enigma was a GOOD scrambler.   
      
   It was reasonably good scrambler.  But rotor part had too small   
   number of positions to resist brute force attack.  And   
   switchboard was much less effective than number of combinations   
   would suggest.   
      
   >   The USA did decode 'Purple', but it was not quite   
   >   as good a code as with Enigma.   
   >   
   >   These days we can kind of just OVERPOWER 1940s   
   >   ciphers ... but mostly it's just that, overpower,   
   >   not so much in the realm of any General Solution.   
      
   Actually, we are still quite far from abilty to brute force   
   108.39 bits keys (effective length of Enigma key), and internal   
   connections of Enigma are worth about 400 bits (and more with   
   additional rotors).  But we know that "know plaintext" attack   
   can be quite effective at recovering keys.  And there are new   
   statistical approaches, likely to break any cipher designed without   
   knowledge of such an attack.   
      
   --   
                                 Waldek Hebisch   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)