<div><blockquote class="gmail_quote" style="margin-top: 0; margin-right: 0; margin-bottom: 0; margin-left: 0; margin-left: 0.80ex; border-left-color: #cccccc; border-left-width: 1px; border-left-style: solid; padding-left: 1ex">
You can't solve it! You must trust at least some client even use<br>SETI/Boinc redundant approach.<br></blockquote></div><br>It does depend somewhat on the problem though; some things are really asymmetric to calculate, and those can be easily verified. For example, if you're setting up a distributed network to crack a sha1 password file, you could send jobs out to millions of potentially untrusted clients. When they return succesful cracks, it's really easy to verify that the client is correct. I'm not sure if this applies to the problem at hand, but there might be some asymmetry to exploit.