An archaeologist wishes to send a valuable artifact to a museum. However, he has doubts as to the integrity of the couriers, and fears they will keep the artifact for themselves if they get a chance to see it. He has a box, and a selection of locks and their keys, but he knows that the museum curator will not be able to open any of them. If he sends a key along with the box, the courier is sure to look inside. What plan do he and the curator devise to ensure that the artifact is safely transported?

Why this works

This riddle hinges on the clever use of locks and keys to ensure that the artifact is secure throughout its journey. The archaeologist first places the artifact in the box and locks it with his lock, ensuring that the courier cannot access the contents. When the box is sent to the curator, he adds his own lock to the already locked box, meaning now it is secured by two locks that only their respective owners can open. The archaeologist then removes his lock and sends the box back to the curator, who can now easily remove his lock and access the artifact. This method ensures that at no point can the courier see or take the artifact, cleverly using the inability of the courier to unlock either lock to ensure the artifact's safety!