[clug] Passwords [SEC=UNCLASSIFIED]

steve jenkin sjenkin at canb.auug.org.au
Sun Aug 26 19:59:27 MDT 2012

Ellis, Peter MR wrote on 27/08/12 11:00 AM:

> Okay, let's get semi-technical military.

Thanks for the good rundown on pads and all.

Bletchley Park, home of GCHQ during WWII, were able to break the Enigma
code, thought by the Germans to be unbreakable because of the huge
number of permutations of the (5?) rotors, their initial settings and
the patch-panel.

One direct impact of this cracking was intercepting orders to the U-boat
Wolf packs. Critical to winning the war.
[For completeness, Enigma was the Cipher, there were printed Code books
as well. They had to be captured through combat operations, leading to
some nail-biting "black-out" periods.]

There were two 'cheats' that GCHQ used to accelerate the process.
[Turing designed the electronic 'Bombe' for the grunt work]

 - military messages are structured.
    There is a known clear-text at the start.
    For completeness, the same message with different headers
    would be sent to multiple stations, allowing other keys
    to be recovered.

 - Operators had their "favourite settings" to start the rotors.
   Girlfriend, service number, birthday, Mother, ...
   Patch panels were changed infrequently.

Yes, I can understand that the Navy would think that "use your service
number" is good advice, and it is if you are the *only* person to do so.
It's known to be really poor advice when almost everyone does it...

Steve Jenkin, Info Tech, Systems and Design Specialist.
0412 786 915 (+61 412 786 915)
PO Box 48, Kippax ACT 2615, AUSTRALIA

sjenkin at canb.auug.org.au http://members.tip.net.au/~sjenkin

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