[RC5] RC5 question

Jerome Lamarque globulle at mac.com
Sat Oct 4 02:32:37 EDT 2003

Hi everyone,

À 18:10 -0300 3/10/2003, Décio Luiz Gazzoni Filho tapotait avec ses 
mimines pleines de doigts :
>The problem is not export restrictions or anything (they've been lifted, as
>far as I know); it's just the sheer amount of work that has to be done. A
>book of mine states that since the inception of the computer through 
>the year 2000, there have been approximately a mole (6e23) of 
>computer operations performed on all computers on Earth. In 
>comparison, there are 3.4e38 RC5-128 keys to check. Even taking into 
>account that only 50% of keyspace is expected to be checked on 
>average, that's 1.7e38 keys, or 1.7e40 cycles. Dividing out 1.7e38 
>by 6e23, you get a number which is on the order of magnitude of a 
>million times the age of the universe.

That's exactly what people said in 1999 about RC5-56 an RC5-64.

Both have been cracked in far less than a century (a few months 
regarding RC5-56, less than 4 years for RC5-64).
I won't even Mention DES-III.
Remember that it's not your computer(s) that's trying to break the code.

Never underestimate computer scientists ;-)

>It's hopeless, possibly short of a breakthrough in quantum computing, or a
>researcher discovering an attack to RC5 significantly more efficient than
>brute force. Personally, I'm not holding my breath.

"Never give up, never surrender"
		Alan Rickman in "Galaxy Quest"
There is a theory which states that if ever anyone discovers exactly 
what the Universe is for and why it is here, it will instantly 
disappear and be replaced by something even more bizarre and 

There is another which states that this has already happened.

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