[Edu-sig] Re: Cryptonomicon

[Dethe Elza]

Bruce Schneier, who wrote the Solitaire algorithm (called Pontifex in 
Cryptonomicon) has an excellent page describing how and why it works:

http://www.counterpane.com/solitaire.html

One of the cool things about it is that it's designed to use playing 
cards, so you can have students encrypt and decrypt messages with cards, 
getting a tactile feel for encryption, then implement the code.  There's 
python code up on the site, too, though they make no claims about its 
reliability:

http://www.counterpane.com/pysol.zip

Anyway, it's much more realistic from an encryption point of view, 
without being much more complicated than a clubhouse algorithm.  Win-win.

--Dethe

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> Today's Topics:
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>    1. Re: Cryptonomicon (Kirby Urner)
> 
> --__--__--
> 
> Message: 1
> Date: Sat, 25 Nov 2000 10:09:40 -0800
> To: edu-sig@python.org
> From: Kirby Urner <pdx4d@teleport.com>
> Subject: Re: [Edu-sig] Cryptonomicon
> 
> 
> I've added some links to my Python-based 
> http://www.inetarena.com/~pdx4d/ocn/clubhouse.html
> including to an URL where Windows users can 
> download GUI simulators of Enigma machines.
> 
> The Sale essay on deciphering the Enigma mentions
> how "no letter my encipher to itself" was actually
> a weakness of the German system, along with its 
> bidirectionality, i.e. if A enciphered to J, then
> J enciphered to A.
> 
> The difference between simple random substitution
> ala my clubhouse code algorithm (which allows 
> self-substitution) and something like Enigma, is
> the latter changes the substitution key with each
> press of a letter (in the Enigma using a complicate
> system of rotors which, like a car odometer, 
> knocked successive wheels one notch with each
> complete revolution of the one before).  
> 
> Here's some example plaintext and corresponding 
> ciphertext, from one of the Enigma simulators:
> 
> Input (note 5-letter chunking):
> 
> AQUIC KBROW NFOXJ UMPED OVERT HELAZ YDOGW WWWWW 
> WWWWW WWWWW WWWWW WWWWW WWWWW WWWWW WW
> 
> Output (note how repeated Ws in the input 
> nevertheless enciphers to different letters
> below):
> 
> UVWFP ALDFF FMNML SHZLI GTMXM CISQU EIYED FJORN 
> OMNRA CZVXL MRBAO JRGRO ZKCAJ NMMLP AO
> 
> Also in the news:  an Enigma machine stolen from
> the Bletchy Park museum was recently recovered,
> along with the internal rotors (found separately,
> according to newspaper accounts).
> 
> Another link shows contains some scans of Turing's
> original typed manuscript re the Enigma, plus 
> there's a virtual tour of Bletchy Park -- all 
> very reinforcing of the storyline developed by 
> Neal Stephenson's 'Cryptonomicon', the novel which
> originally inspired me to launch this thread.
> 
> It's be high feasible to write an Enigma simulator
> in Python of course, including with a GUI front 
> end.  But in accordance with my "cave painting"
> analogy, I think what's important from a pedagogical
> point of view is, on first pass, to give just the 
> flavor, the essential gist, and then move on to
> linked topics (e.g. digital circuit design and 
> the evolution of computing hardware).
> 
> Kirby
> 
> 
> 
> 
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