ABSTRACT
The introduction of public-key encryption marked a revolution in cryptography. Until that time, cryptographers had relied exclusively on shared, secret keys to achieve private communication. Public-key techniques, in contrast, enable parties to communicate privately without having agreed on any secret information in advance. As we have already noted, it is quite amazing and counterintuitive that this is possible: it means that two people on opposite sides of a room who can only communicate by shouting to each other, and have no initial secret, can talk in such a way that no one else in the room learns anything about what they are saying!
