Feature Request: Proof of Work Signed Extension

[JesseAbram]

The idea is to build a proof of work signed extension to optionally allow free txs on chain if a user client side PoW.

Flow

• User first creates a PoW proof using items in their transaction (nonce, address, so people can't reuse other's PoW)
• User submits this with their tx
• The proof of work difficulty scales with the usage of the chain

This is inspired by Hal Finney's usage of proof of work in emails as verifying proof of work is easy at the node level but trying to spam the chain with significant amounts of txs would become computationally intense

[apopiak]

@thiolliere The idea I mentioned Jesse had.