There MUST be a more efficient way than brute-force.
Of course a reverse hash function would be the golden ticket.
More attainable might be some function to produce a smaller set to brute-force.
Watch out Satoshi!...

reverse hash is just nonsense, Ill hash a video file for you and give you the hash, then you have to reverse the hash to the original video file, there is no way this can be done.