Riddles, brain puzzles and mathematical problems

[PutraenusAlivius]

Darn :\ Hmmm... this probably won't work, but can we ask the friend to send us a lock for the box?

They'd have the key already and no one else could open it without a lockpick

You are close. How is your friend going to send you the lock without it being stolen?

He would hide it probably in his shirt, go to the place and give the lock.