Riddles, brain puzzles and mathematical problems

[CarnivorousJelly]

You want to send a valuable object to a friend. You have a box which is more than large enough to contain the object. You have several locks with keys. The box has a locking ring which is more than large enough to have a lock attached. But your friend does not have the key to any lock that you have. How do you do it? Note that you cannot send a key in an unlocked box, since it might be copied.

NOTE: Your friend is intelligent and can understand your plan even if you can't communicate.

Use a lock with the code, then send a separate letter with clues to the combination code.

Or can we not do that? o: