King Charles want to send the diamond ring to his girlfriend securely.He got multiple locks and their corresponding keys.His girl friend does not have any keys to these locks and if he send the key without a lock , the key can be copied in the way.How can charles send the ring to his girl friend securely .
charles put the ring into the box, secure it with one of your locks, and send the box to the girl firend.
She should then attach one of his own locks and return it. When you receive it again, remove your lock and send it back with her lock. Now she can unlock his own lock and retrieve the object.
