[RC5] Estimated time of completion of DES-II-2, please.

Jason Untulis untulis at netgate.net
Mon Jun 22 16:17:36 EDT 1998


"Hugo Villeneuve" <Hugo_Villeneuve at videotron.ca> said:

: Could someone calculate an estimation of the duration of the upcoming
: DES-II-2 challenge by comparing the data aquired in the first contest
: with the growth that we had since. This could help us to see if we'll
: get the full 10 000$ prize, because we have now to find the key in 10
: days!

It's not too hard to do a back of the envelope calculation in two
different ways. Both are probably still in the same order of magnitude,
but could probably be off by a factor of 2 easily.

o We're currently doing ~.01%/day of the rc5-64 keyspace. Given that a
  client will do roughly double the number of DES keys than it will RC5
  keys (because of the parity bit pairing) and that the DES keyspace is
  256 times smaller than RC5-64 (same number as RC5-56), that gives you
  around 5%/day of the DES keyspace.

o A more accurate estimate comes from the comparative stats page at
  <http://www.distributed.net/statistics/stats.html> (note this hasn't
  been updated for a week...) This gives us about 3.4x DES-to-RC5 ratio
  (although this doesn't scale since it's based upon completed block
  distribution by machine and reference CPUs representing an entire
  architecture). That would put us around 8.5%/day, if it scaled.

Given 10 days, that gives us good to excellent odds of finding the key
fast enough to get the US$10K.

Neither of these calculations take a few important factors into
consideration:

o The switchover (alluded to in an earlier post). For example, all the Mac
  people (including myself) who run the Meggs' graphical client rather than
  the DeNitto dual core client. My guess is that we'll effectively lose at
  least a day's worth of distributed.net's power because of this, although
  some of it is inevitable.

o The new 2.71 clients are supposed to have faster DES cores and be primed
  for the switchover. The adoption rate of these clients will probably be a
  significant factor. (see last State of the D.N Address)

o Those people who left distributed.net for other projects (Golomb rulers,
  Mersenne primes) because they think that RC5-64 is a waste of time, but
  that the DES contests aren't and come back to add to the DES contest.
  (This wouldn't be a problem if v3 actually made some progress in
  increments smaller than 3 months (and growing), hint, hint.)

o Those people running clients w/o DES versions available (graphical Mac,
  VMS, QNX, DGUX) won't be able to contribute to the DES contest. The GUI
  Mac clients probably represent the vast majority of these.

o Server I/O apparently may be a factor if a couple UW SCSI disks aren't
  found/bought/donated. (see the latest State of the D.Net Address)

HTH.
-- 
Jason Untulis, Ravenous Media Consumer    /\    /        untulis at netgate.net
<http://www.netgate.net/~untulis/>    \  /==\  /          untulis at netcom.com
protected by spamgard[tm]              \/v2.4\/  untulis at leland.stanford.edu
PGP key soon            (C) <http://www.netgate.net/~untulis/copyright.html>

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