Find the solution to the following puzzle: Shipping the diamond. A person must send a 200 carat polished diamond (or something quite valuable) to a customer, through an untrustworthy carrier, who supplies the person a container but does not know the contents that will go into the box. The sending person and the recipient customer both have a lock with a key that is not identical. The carrier’s transportation can be repeated. How will the sending person securely send the diamond to the customer without the carrier taking the contents and run away with it? What is the concept behind the solution?