[RC5] RC5-64 HAS BEEN SOLVED
Robert A. Rosenberg
dnet at rarpsl.com
Sat Sep 28 01:42:03 EDT 2002
NOTE - THIS IS A RE-SUBMISSION OF A POST I MADE FRIDAY EVENING THAT
WENT OUT UNDER AN ADDRESS THAT IS NO LONGER VALID (AND WHICH WAS NO
LONGER SUBSCRIBED TO THE LIST).
At 09:40 -0700 on 09/27/2002, Jason Hartzell wrote about RE: [RC5]
RC5-64 HAS BEEN SOLVED:
>> We needed nearly 5 years for rc5-64.
>> If time needed decreases by a factor of 5 we would need 256 years to solve
>Just because CSC, RC5-64 and the last DES challenge went through such a
>large percentage of the keyspace doesn't mean RC5-72 will. It could be ANY
>key. As unlikely as it may be, it is very possible that RC5-72 could be done
>before the end of this year (provided clients are out before the end of this
>year). To make a direct comparision just seems absurd. There is no reason to
>believe that it will take the EXACT same percentage of the keyspace to find
>RC5-72, or RC5-80, or RC5-128.
There is also the fact that as the RC5-64 project progressed, there
were more (and more powerful) machines working on the project. To get
an accurate idea, you have to map the percentage of completeness
against time. In fact, if we froze the number and mix of machines
working on RC5-64 as of 23Sep2002 and started them all working on the
problem from scratch (feeding the blocks out in their original return
order [so as to suppress the "right" key until the end and not issue
it when it originally was issued but never returned]), I think it
would only take 6-9 months [maybe less] to issue the key (at the
current processing rate).
RC5-72 will show just the same type of curve as RC5-64 as more
machines join, more powerful machines (and code) get used, etc. Most
of the work will get done just prior to the solution as the
processing rates ramp up.
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