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>it's that you cannot bypass it at scale.

Define "scale". For any reasonable wait that you're willing to impose on your users, any PoW scheme heavily favors attackers. They have unlimited time and can be scraping even while they're asleep. Your visitors on the other hand don't have that luxury. You might argue that's not the point and it's only to stop dumb scrapers that are effectively ddosing your site, but if it's just dumb scrapers, you could've stopped them less onerous measures like tls or javascript fingerprinting.

by petu13 hours ago|

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If algorithm used is static and GPU-friendly, then what stops bypass at scale?

by drum5513 hours ago|

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It's more or less designed for it, it's SHA256 with a break in the middle for midstate compression to be effective, and the difficulty system is based on a misunderstanding of how bitcoin PoW works ("number of zeros" is never, ever a consideration in bitcoin, it's a match to a floating point target).

sha256(challenge + ascii(nonce)) means that the first compression round of the function can be cached and the second compression round is just the nonce plus the cache. This is the same trick used in Bitcoin mining and would have been avoidable by putting the nonce first, so immediately any non-naive code has to do half the proof of work as the vanilla solver.