Reading on EtHash, I was thinking if it is possible to verify the current Ethereum Proof Of Work by a smart contract. There is an instruction SHA3, which computes 256-bit hash, but EtHash uses 512-bit hash. Was this discrepancy intentional or just an oversight? Is it possible to compute one from another somehow?
I know that verifying PoW in the contract might be expensive, but it could be used just as a response to a challenge.