We always wonder who the real master mind behind the name of Nakamoto Satoshi the creator of bitcoin is.But what exactly would make you believe or convince you that "this" person is Satoshi if he/she ever decided to reveal himself.
There might be infinite wannabes and glory hunters wanting to rise to fame ,given the real Satoshi is one among them how would you go on about finding the right person.
Signing a message with the key to the genesis block, or other well known block mined by Satoshi would be strong evidence that the person might be Satoshi.
Of course it could be someone else that stole the key, but at least it's a start.
Anyone that just says so has zero credibility.