[RC5] First Impressions

Jeff Lawson bovine at distributed.net
Fri Mar 6 03:37:58 EST 1998


>>       There is one potential problem with searching from start to end. It
could
>>be possible for someone with this knowledge about D.Net to organize a
contest and
>purposefully >pick a key near the end.
>
>
>I was thinking about that a while ago.   Would one way to combat that
sneaky trick
>(not that I'm suggesting it would be employed of course!) be to search the
keys in a
>sort of 0-1%, 10-11%, 20-21%, etc, then 1-2%, 11-12%, or just randomly of
course ?
>
>How do d.net do it ?   Did we go from 0% towards 100% trusting it was
randomly
>picked ?



We started out searching DES randomly, however soon after starting we
learned of the possibility of coordinating with Rocke Verser of deschall,
and promptly switched to linear distribution so as to conserve the keyspace
for his clients.  When the technical details in keyordering between the two
clients were worked out, it was found that we could conveniently map the key
ordering of the Deschall clients into the extreme upper portion of our own
keyspace (with only a few, easily calculatable regular gaps due to key
ordering differences).

RC5-56 was started linearly, but was switched to random distribution ~15%
through or someplace.  RC5-64 is being randomly, but restricted to 56-bit
"subspaces"


Jeff
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