John Pavlus
For thousands of years, if you wanted to send a secret message, there was basically one way to do it. You’d scramble the message using a special rule, known only to you and your intended audience. This rule acted like the key to a lock. If you had the key, you could unscramble the message; otherwise, you’d need to pick the lock. Some locks are so effective they can never be picked, even with infinite time and resources. But even those schemes suffer from the same Achilles’ heel that plagues all such encryption systems: How do you get that key into the right hands while keeping it out of the wrong ones?
The counterintuitive solution, known as public key cryptography, relies not on keeping a key secret but rather on making it widely available. The trick is to also use a second key that you never share with anyone, even the person you’re communicating with. It’s only by using this combination of two keys—one public, one private—that someone can both scramble and unscramble a message.
To understand how this works, it’s easier to think of the “keys” not as objects that fit into a lock, but as two complementary ingredients in an invisible ink. The first ingredient makes messages disappear, and the second makes them reappear. If a spy named Boris wants to send his counterpart Natasha a secret message, he writes a message and then uses the first ingredient to render it invisible on the page. (This is easy for him to do: Natasha has published an easy and well-known formula for disappearing ink.) When Natasha receives the paper in the mail, she applies the second ingredient that makes Boris’ message reappear.
No comments:
Post a Comment