Puzzle:: "Love in Chor-Bazar"

Question: Veru and Basanti have fallen in love (via the internet) and Veru wishes to mail her a ring. Unfortunately,they live in Chor-bazar where anything sent through the mail will be stolen unless it is enclosed in a padlocked box. Veru and Basanti each have plenty of padlocks, but none to which the other has a key. How can Veru get the ring safely into Basanti’s hands?

C'mon think
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Ans: Veru sends Basanti a box with the ring in it and one of his padlocks on it. Upon receipt Basanti affixes her own padlock to box and mails it back with both padlocks on it. When Veru gets it he removes his padlock and sends the box back to Basanti;

This solution is not just play; the idea is fundamental in Diffie-Hellman key exchange, an historic breakthrough in cryptography.