[RC5] [ADMIN] DES-II-2 is over...

Mary Conner trif at serv.net
Fri Jul 17 14:56:21 EDT 1998



On Fri, 17 Jul 1998, Pete Krawczyk wrote:
> Which means someone should crunch the "winning" block today.

The most effective search of a DES keyspace is not linear.  Their
permutation of the keyspace may not have resembled a simple linear
march through the keyspace at all.

> If that's true, then also the point should be made that this
> computer is apparently 2 times as fast as the whole d.net machine
> at this point.

They claimed 88 gigakeys, which squares with our rough calculations
(25% of keyspace over 56 hours, which yields 89.3 gigakeys).  I have
personally seen keyrates of 75 gigakeys off the proxyinfo page.  
Certainly our overall rate since the start is much less, but d.net
was not that appreciably slower than the EFF machine.  We also did
not have anything near full conversion.

> Working with the EFF, we can hand them huge size
> blocks (probably like 2^50 blocks) and have them crunch them.
> And if they get the right key, we can donate 8 of the 10k to them -
> for I'm sure if EFF tripled our power, people would be more inclined
> to vote for them as the $6k recipient.

rc5 is not vulnerable to the same parallelizing attacks that makes a
hardware DES cracker feasible.  If you have lots of 64 bit registers, you
can crack 64 DES keys with only a little bit more work than doing one key. 
The same is not true of rc5.


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