[rc5] Tardy keyblocks

Eric Gindrup 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


[snip]
     
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.  
     
     [snip]
     
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...).
     
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