Random checks won't be very good in detecting bad clients. They could introduce random errors on only 1/1000 of the returned data -- and if only 1/1000 of the data is checked then your probability of detecting a 1 in 1000 error drops to 1e-6.
The only way of getting reasonable results from untrusted clients is to have the results computed independently by N clients. You could also first try to get the problem solved, get a prelim answer to play with and then continue to do the verification.
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The only way of getting reasonable results from untrusted clients is to have the results computed independently by N clients. You could also first try to get the problem solved, get a prelim answer to play with and then continue to do the verification.
--André