[RC5] Blocks missing

Bruce Wilson bwilson at distributed.net
Fri Apr 12 12:42:01 EDT 2002

>In the previous rounds of this discussion there was never a clear
consensus on why there would be uncredited works.  It seems to happen to
often and too regularly for it to just be colliding with random blocks,
unless there have been a massive number of random blocks done in
keyspaces that shouldn't have been allocated to random blocks.

All keyspaces have been handed out at least once.  If the person who
first got a work unit took a long time to finish it (downloaded too many
work units, for example), it's possible that they turned it in sometime
after you downloaded it the second time around (or third, or...).

There are no "keyspaces that shouldn't have been allocated to random
blocks" anymore.  At one time, all clients were directed to use a single
keyspace for randoms, determined by the network.  Now the keyspace for
randoms is generally one or two keyspaces ahead of the one we are
currently handing out.  I'm not sure of how the keyspace for randoms is
selected, but I know it's been automated, where it used to be manually
assigned by someone.

I haven't investigated your situation, but it's very possible that
randoms account for a significant portion of your observed problem.
Corrupted packets or mistyped e-mail addresses can also account for

As it was with CSC, as we approach the end of the keyspace for RC5-64,
it becomes more and more important for people to download only the
workunits they can complete in a reasonable amount of time.  The closer
we get, the faster we will be recycling keyspaces, and the more likely
your work will be a duplicate if you sit on it too long.  (Not to
mention the fact that the more times we recycle, the more people have a
copy of each work unit, so the odds of a collision climb even faster.)

We learned some painful lessons with CSC.  This time we're determined to
do better.  We're putting together a solid plan for how to deal with
"endgame" situations to make sure our participants know what's going on.

Bruce Wilson <bwilson at distributed.net>
PGP KeyID: 5430B995, http://www.toomuchblue.com/ 

Build a man a fire and he'll be warm for a day.
Set a man on fire, he'll be warm for the rest of his life.

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