pool freeriding exploit?

[unk]

i don't recall this ever being mentioned, but i might have missed it: nothing prevents participants in pools from sending to the pool all proof of work that pays a reward except hashes that satisfy the block chain's current difficulty. in withholding such hashes, pool participants give up (1) an insignificant amount of revenue (the reward for the withheld hash) in exchange for (2) avoiding a statistical contribution to increased difficulty in the block chain and (3) the opportunity to harm a competing (or otherwise out-of-band targeted) pool.

(3) on its own may motivate such an exploit. it is an empirical question, i believe, whether (2) outweighs (1) in any particular case.

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[DrHaribo]

This is the "block withholding attack". It is very old.

[organofcorti]

It's an attack that has been nicely analysed here: https://bitcoil.co.il/pool_analysis.pdf Section 6.2