Sharing Keys

Ralph Merkle was an undergraduate at Berkley when one of the Computer Science courses he took got him thinking about an intriguing problem... a problem that prevented widespread use of computers for business. Still an undergraduate, he came up with a revolutionary solution. A solution that has changed the world of business and computer privacy - and even beaten the Spooks at their own game.

The problem was this. How can you have a private online communication with someone you have never met before (eg between you and your bank over the internet, for example). The tricky bit over the internet is that other people can easily read everything you send.

The obvious answer is use a code and encrypt your conversation, but codes need digital keys - a secret shared only between the two of you, that's used to turn the message to gibberish and back. That just moves the problem though: how do you share a secret key without giving it to the snooper at the same time if you don't already share one?

Today such communications happen all the time. Ralph Merkle's undergraduate idea was one of the sparks of inspiration that made it possible.

What was his idea? It was based on puzzles.