You want to send a valuable object to a friend securely. You have a box which can be fitted with multiple locks, and you have several locks and their corresponding keys. However, your friend does not have any keys to your locks, and if you send a key in an unlocked box, the key could be copied en route.

How can you send the object securely?

The only solution I can think of is you send the object in the box with a lock. Your friend then fits another lock and sends it back. You remove your lock, send it back again then the friend can take his lock off and open it. I don't know whether we can assume the friend has his own locks, though.

Posted by Lewis on 2003-07-21 20:56:45