[rc5] RC64 keyspace
gindrup at okway.okstate.edu
Tue Oct 28 11:28:54 EST 1997
I'm more worried about the storage method for assigned and returned
blocks. There appears to be a difficulty where an interrupted client
loses a block. By itself, this is irrelevant. However, having single
blocks drop out here and there makes the set of assigned and not
returned blocks "interesting", i.e. hard to represent compactly.
Assuming that one bit is used to record the assignment of a block
and one bit is used to record the receipt of a block, 2^65 bits will
be needed. This is 2^32GB (4 Exabytes). I don't know where *I* would
go to look for a storage system of that magnitude...
If the set of "tardy" blocks was simple, then extent methods could
be used to represent the sets of assigned blocks and returned blocks.
Given the method of assigning, such a representation is probably
already in use for assigning. This still leaves a potential for 2EB
of returned block data. Of course, if the loss rate is < ~1/16, then
extents might be more efficient.
In any event, I'd expect that the Bovine crew is going to need
about 256-times as much storage for this information as was used in
-- Eric Gindrup ! gindrup at okway.okstate.edu
______________________________ Reply Separator _________________________________
Subject: [rc5] RC64 keyspace
Author: <rc5 at llamas.net > at SMTP
Date: 10/27/97 10:46 AM
I was really hoping that the D.N. wasn't going to move onto the 64bit
challenge, but since we cracked the 56 so quickly I don't have anything
else to use my cycles on.
What I was really wondering was whether we could use some analysis
techniques to check high probability key space segments first, instead of
just randomly checking the entire keyspace? I read some information on
this early in the 56bit days, but don't remember the specifics. Has this
already been ruled out?
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