[rc5] Tardy keyblocks
gindrup at okway.okstate.edu
Tue Aug 26 14:43:03 EDT 1997
When the unchecked keyspace in tardy blocks exceeds the unchecked
keyspace in unassigned blocks, it is more effective to check a tardy
block than an unassigned block.
Assuming that half of an average tardy block is known to not
contain the target key (else the effort would have terminated) then
when the number of tardy blocks is greater than twice the number of
unassigned blocks, it is more logical to work on a tardy block than on
an unassigned one.
-- Eric Gindrup ! gindrup at Okway.okstate.edu
______________________________ Reply Separator _________________________________
Subject: [rc5] Tardy keyblocks
Author: <rc5 at llamas.net> at SMTP
Date: 1997/08/26 13:29
However, there is no mechanism by which a tardy block could be transmitted
to a client where it would not be equally effective to transmit an
unassigned one. If there is no net connection, neither can be transmitted
(hence the need for random blocks), and if there is a connection, both can
be transmitted. The idea of saving tardy blocks for periods of no
connection is no better than saving unassigned blocks for periods of no
connection. The idea of giving clients some manner of better-directing the
generation of random-blocks does have merit.
Whatever resources are used in buffering tardy blocks can be used just as
effectively in buffering unassigned ones. I submit that the latter is a
more effective strategy.
I don't mean to be stomping on anyones ideas. I just don't think that
from a logical standpoint there is any reason whatsoever to worry about
them now - except for the developers to be prepared to assign them on a
moments notice once the keyspace is exhausted (we don't want people to
defect while the servers are being re-coded to handle tardy keys).
If anyone really thinks that there is a hole in this argument, then please
let me know. I've seen really complicated mathematical arguments about how
tardy keys are better than random ones, but I don't believe that this is
relevant - nobody argues that random keys are better than tardy ones - only
that there are instances where you simply have to fall back to something,
and random keys are the only alternative (because there is no value in
buffering a tardy key over an unassigned one...).
Richard T. Freeman <rfreeman at netaxs.com> - finger for pgp key
3D CB AF BD FF E8 0B 10 4E 09 27 00 8D 27 E1 93
http://www.netaxs.com/~rfreeman - ftp.netaxs.com/people/rfreeman
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