Riddle: I am a helpful creature– I'm not too big and not too small. Out of all my fellow reindeer, you could say. I’m the fastest of them all. Who am I?
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.