I want to mail a necklace to my wife, but anything sent through the mail will be stolen unless it’s sent in a padlocked box. A box can bear any number of padlocks, but neither of us has the key to a lock owned by the other. How can I mail the necklace safely to my wife?
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SelectClick for Answer |
I put the necklace in a box, add a padlock, and send it to my wife.
She adds a second padlock and mails it back.
I remove my padlock and send her the box, and she opens it.
Dartmouth mathematician Peter Winkler writes, “This solution is not just play; the idea is fundamental in Diffie-Hellman key exchange, a historic breakthrough in cryptography.”
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