[rc5] Possible further d.n projects.

Brian Murphy brianm at earthlink.net
Thu Oct 23 21:32:09 EDT 1997


	First, I'd like to preface this by saying "I'm no crypto guru, but:"

Lets look at the previous plaintexts for the RC5/40, RC5/48, RC5/56, 
and DES challenges.

RC5/40:  The unknown message is: This is why you should use a longer key

RC5/48:  The unknown message is: The magic words are Security Dynamics and RSA

RC5/56:  The unknown message is: It's time to move to a longer key length

DES:  The unknown message is: Strong cryptography makes the world a 
safer place

Hrm.  I'm noticing alot of similarities here.  There seems to be a 
very common theme.  Again, I'm no crypto guru, but if I were to mount 
a chosen plaintext attack, all of these words would be on my list.  
Doesn't it seem fairly likely that RSA has done something 
*relatively* similar in at least one more of these contests?  Look at 
how amazingly similar the RC5/40, and RC5/56 bit messages were.  

	What is the feasibility of mounting a chosen plaintext attack 
against the other challenges?  If feasible, it would *certainly* be 
less computationally challenging than a brute force attack.  Am I 
missing something, or would it be *DAMN* cool to announce that we'd 
just solved RC5/90 ?

	On another note, I think attacking RSA-155 sounds like a worthy 
effort.  It sounds a hell of alot more useful than kicking Kasparov's 
ass at chess(although it would be kinda groovy to say 
..."Kasparov?  What a wuss.."
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