[rc5] Suggestion for protocol

Honza Pazdziora adelton at informatics.muni.cz
Tue Jun 24 14:59:02 EDT 1997


> Honza Pazdziora <adelton at informatics.muni.cz> writes:
> 
> > This would prevent people from downloading blocks and reporting them
> > back as negetive without ever looking at them.
> 
> There is another tactic as well:  Have the key server send out known
> good keys from time to time and see if they are reported as bad or
> not.
> 
> If
> 	(1) the blocks sent out are more random than they are now, and
> 	(2) the client doesn't brag when it finds a good key,
> 
> this would work.

If I understand you well, each time you would be sending the key you
would also send out the cryptotext and time to time you would issue
different cryptotext and "solution-found" block for it. But, if
anybody would want to cheat, he would simply ignore the loads
containing your test cryptotext (do not ask me why people do that, but
some simply do :-( Or would compute them to look like good guy and
simply cheat on the next load.

> The other possibility would be to embed an encryption key within the
> client itself, and have it use that as authentication.  That really
> sucks, but it would work.
> 
> Of course, you could also require that the PERSON running the
> client register themselves and get a special secret key.  When
> returning blocks to the server the key would be used.  If one
> specific key started sending in bad results (tested by sending it
> known good blocks from time to time) it could be silently ignored
> from then on.  Don't drop the client, just send it already computed
> blocks and let the spammer think they're getting away with something.

But, to give the client the good block, you need to give it the
cryptotext as well (we do not know _the_ good block yet). And if you
give different cryptotext from the competition one, you distiguish the
testing loads.

Somebody here mention Zero knowlegde proof and my suggestion was based
on similar ideas. You do not let the client know what part of his work
will be checked, so it needs to do all the work.

------------------------------------------------------------------------
 Honza Pazdziora | adelton at fi.muni.cz | http://www.fi.muni.cz/~adelton/
                   I can take or leave it if I please
		     Thanks for having done your DES.
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