[Edu-sig] Cryptonomicon

Kirby Urner pdx4d@teleport.com
Mon, 20 Nov 2000 05:35:21 -0800

>I can see some interesting discussions about what it means to be random,
>and what sorts of characteristics we might want from a 'random' activity
>in different situations.

Yes, always a worthwhile thread.

Also fun would be to take some clubhouse crypto texts and 
crack them.  Although permuting the 26 uppercase letters 
yields 403,291,461,126,605,635,584,000,000 possible 
arrangements (looks impressive), if we know the plaintext 
is in English, then we can always apply some valuable clues, 
e.g. letter frequency, in descending order, tends towards 
ETAOINSHRDLU, plus we have commonly occuring letter combos, 
like ET EA OU.

And if the encrypted text isn't chunked (e.g. into 5-letter
strings), to obscure word lengths, then we have a lot more 
to go on:  frequent 3-letter words like AND THE would 
suggest substitutions.  Indeed, finding the most common 
letter (say V) and then finding 3-letter words ending 
in V would give a good hypothesis for the T and H 

I'd be in favor of leaving all these clues intact (e.g. 
not even chunking at first) and allowing students to 
successfully crack a few clubhouse messages.  Then you 
could go to a next level of difficulty (e.g. add chunking).  
As per usual, the cryptographer and cracker share the 
same mind, as do computer security folks and hackers (in 
the popular media sense of hacker).