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Old 2003-11-21, 01:44   #1
schneelocke
 
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Default Masked residue

Hi everyone,

here's yet another question from your resident newbie wolf. This time: why are the Lucas-Lehmer residues on the PrimeNet status page for an account masked partially?

Thanks!
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Old 2003-11-21, 02:08   #2
garo
 
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To preserve the integrity of the result. All exponents are doublechecked and the residues are compared. If the residues were not maskes someone could submit a result with the correct residue without having done the work.
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Old 2003-11-21, 02:12   #3
schneelocke
 
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That explains it. Thank you!
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Old 2003-11-21, 22:22   #4
Gary Edstrom
 
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Quote:
Originally posted by garo
To preserve the integrity of the result. All exponents are doublechecked and the residues are compared. If the residues were not maskes someone could submit a result with the correct residue without having done the work.
That brings up a second related question: Why are only 2 characters masked? It would seem to be a lot more secure if it went 50-50, only displaying the first 8 characters of the residue.
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Old 2003-11-21, 23:49   #5
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2 characters already mean there are 256 potentially correct residues, and from what I know about the Lucas-Lehmer test, I think you can't easily reconstruct which digits actually are correct without doing the whole test.

Still, you're right, of course. One might even ask why any digit of the the residues is given when they are not yet doublechecked.
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Old 2003-11-22, 01:03   #6
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It's a balance between leaving enough information to keep participants intrigued and involved and security.
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Old 2003-11-22, 01:26   #7
schneelocke
 
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*nods* But the participant themselves can always get the full (unmasked) residue from their log file, anyway...
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