[RC5] At 10 Billion Per Second

Glen Hoag hoag at ro.com
Fri Apr 24 21:34:58 EDT 1998

At 2:39 AM -0500 4/24/98, Michael Heacock wrote:
>Hash: SHA1
>I was looking at the stats page.  Currently we are averaging about 12
>billion keys per second.  At this rate would it take us 48 years to
>crack the key (given that the we need to solve all the keys before

That assumes that the keyrate is constant.  It is not.  There are several
factors that come into play:

1. We have been accumulating participants over time.
2. Users upgrade their machines, so the average participant's keyrate
increases over time.

Over the past eight weeks, our rate has been increasing *very roughly*
linearly at about 89Mkeys/sec/day.  (this is based on a visual curvefit of
the eight week plot of the keyrate at
<http://www.distributed.net/statistics>)  If this is a valid approximation,
we would exhaust the keyspace in roughly 2000 days, or about five and a
half years.

Other projects (the DES-II series of contests, for instance) will draw
computing power away from RC5-64, so there is no way to tell, given the
small sample so far, when the keyspace will be exhausted.  Since the key is
at a random point in the keyspace, we probably will not have to check every
key to find the correct one.  DES-I and RC5-56 fell relatively early in the
search.  DES-II-1 fell near the end.

>Perhaps my calculation is wrong (if so, please correct), but I suspect
>we need a lot more processing power (i.e. a lot more computers in the

Lots more computers would certainly help the situation, but the picture is
nowhere near as bleak as your calculation suggests.

--Glen Hoag
  hoag at ro.com

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