[rc5] rc5 crack schemes

Eric Gindrup gindrup at okway.okstate.edu
Mon Aug 25 14:17:34 EDT 1997

     Well, it may be that any such "neural system" is the same sort of 
     black box that the Swiss neural tank seekers are.  Nobody knows how 
     they work, but they were trained on a significant sampling of a 
     population and seem to work really well.
     Similarly, one could imagine training a neural net to guess key bits 
     given the cipher-text.  Perhaps there are effective cryptanalytic 
     techniques.  If we don't know them , then there is some non-zero 
     chance that a trained neural net might stumble on one or part of one.  
     Then the neural net has a better idea of what is the key than the 
     people who trained it.  However, guaranteeing that the training is any 
     good would be many more times more compute-intensive than the Bovine 
     effort.  Of course, if any agency were to attempt it, the NSA would be 
     the most likely to succeed.
     BTW: Neural and genetic algorithms (to pick two silver bullets at 
     random) don't magically solve all of our problems.  Just like 
     simulated annealing they occasionally make exceptionally good guesses 
     about the right form of solution.  Cryptography is slightly kinder to 
     the digital neural net because the inputs and outputs are entirely 
     discrete.  This does not mean that running a few 10^15s of encrypted 
     messages past one and training it to produce the key is necessarily 
     going to work.  It's still a black art to make a neural net do better 
     than the programmers at some task...
            -- Eric Gindrup ! gindrup at okway.okstate.edu

______________________________ Reply Separator _________________________________
Subject: Re: [rc5] rc5 crack schemes
Author:  <rc5 at llamas.net> at SMTP
Date:    1997/08/25 10:25

If each key has an equal probability, how could this magic neural 
net work?  
The only better way is if one could come up with a cryptanalytic 
attack that is less costly than brute force.
If there is substance to this rumour, then bring it to light so that 
the world might be warmed and enlightened.

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