[pishpash]

Proof of work isn't a big concern if the hard problems are also economically valuable to solve; there are myriad such problems.

[TylerE]

No they aren't.

For a PoW to be valuable it needs to be cheap to verify. Hard problems usually aren't.

[pishpash]

What? Any NP-complete problem is "cheap" to verify vs. to solve. You're telling me there are no economically valuable NP-complete problems?

[TylerE]

If there are, why has no one built a coin around it unstead of using untold watts to calculate hashes?

[setr]

They did, like protein folding.

Part of it is that if its going to be a currency, its not particularly appealing that some group gets arbitrary benefits from the act of mining, for free. The government has the power to force such a currency on us, but otherwise, unless the economically valuable activity is globally valuable, its a difficult proposition to justify.

[kirillseva]

umm, generating a block whose hash starts with N consecutive zeroes (e.g. 000000009A8C3...) seems to be exactly that - an NP hard problem that's trivial to verify in polynomial time.

[TylerE]

yes, but it's not useful in someway outside of the blockchain, which was the thrust of GP's argument.

[setr]

Isn't the entire NP class hard to solve, cheap to verify? Im sure some economically valuable problem can boil down to an NP problem...

[nambit]

Most solutions to NP problems are cheap to verify.

[Ar-Curunir]

What you want are "moderately hard functions": functions that are neither easy nor excessively hard.

[TD-Linux]

If a proof of work solution is economically valuable to solve, the hashrate will just increase to the point where it's just marginally profitable again.