Secret Mail Puzzle
The Puzzle:
You want to send a secret message to your friend Alex in the mail. |
But you can't send a key, because Sam could use or copy it!
How can you get your message through securely?
Send the box with the lock to Alex.
Alex can't open it, but can put another lock on the box.
Alex sends this box with the 2 locks back to you, you unlock your lock and send it back to Alex again.
So there is just Alex's lock on the box and Alex can now open it.