Can a Finney Attack Be Used to Double-Spend in a Proof of Work System?

A Finney attack is a type of double-spending attack that can be used in a Proof of Work system. It involves a miner who pre-mines a block containing a transaction that sends coins back to themselves.

They then send a conflicting transaction to a merchant and, at the same time, broadcast their pre-mined block. If their block is accepted by the network first, the transaction to the merchant will be invalidated, and the attacker will have successfully double-spent their coins.

This attack is difficult to execute and requires the attacker to be a miner.