Question

Hello Can someone help me with this problem?

Bob and Alice want to send each other secret messages that no one else will have access to. They have decided that they will use a locked box to hold the secret messages, and they will drop the box off in each other’s mailboxes. The problem is that if they use a combination lock, they will have to send the combination to the box and someone might intercept it. Here are the materials they have access to:
A box that can be locked with a combination lock
Two combination locks (the kinds that click shut that you might use on a school locker)
Paper
Pencil
Describe a protocol Bob and Alice can set up to deliver these messages securely.

Answer 1

Step-by-step explanation:

Bob and Alice could first send each other their open locks. Then, e.g., Alice can send a message to Bob and lock her box with Bob's lock, and vice-versa.

A more real-world approach to this problem is that they use a form of Diffie-Hellman approach to exchange a combination for the lock.

Diffie-Hellman is an algorithm where you can exchange secrets even if you know someone is intercepting each and every message you exchange. It's a bit mathematical, but still very cool.