love in kleptopia

[BMAD]

John and Mary have fallen in love. John wants to send Mary a ring through the post but in their country of Kleptopia, any package that is not locked will have its contents stolen. John and Mary have plenty of padlocks but neither has the other's key. How can John get the ring safely to Mary?

[bubbled]

Should be:

 

By a lock-box that can hold two locks. John puts the ring in the box, locks it and sends off to Mary. When Mary gets it, she adds her lock to the box and send back to John. When John gets the box back, he takes off his lock and sends back to Mary.

[The_unbeliever]

John sends the ring to Mary in a locked glass chest.

- Mary can break the chest open with an hammer
- Since the chest is locked, no one will steal from it

[jasen]

Should be:

 

Hidden Content

This is a subject in cryptography

A don't want to send his key to B.
B also don't want to send his key to A.
But they want to communicate in insecure Internet connection.
So they have to use an encryption method which work like this.
Only commutative encryption method can answer this problem.

[The_unbeliever]

Should be:

Hidden Content

Yep, sorry. I forgot to use Spoiler, and the "edit post" button disappeared on me.

I have a hard time understanding the 2nd one... I'll think about it a bit more - I suppose a play on words would be a poor answer.

Edited September 29, 2015 by The_unbeliever
Edit: I take it that's because I've submitted an "answer", not a regular post....

[Deepa]

John send the locked box to Mary. She will lock it again using her padlock and sends to john. John will open the lock which he is locked and sends to mary. Mary will have the key of her padlock n open it n take the ring