But he could at any time transfer the funds and make the treasure hunt ... a rip off.
It is more a sort of trap to waste computing power / time
Not necessarily, if he just sign a message with the puzzle address we'd surely try to solve the puzzle, after making sure it's a legit one.
....
First of all sign a message. But even in that case we cannot trust he will love the funds before the puzzle has been solved
dear Dylan41, just sign a message please it's that simple. We're waiting for your respond.