How to trick other people's computers into solving your math problems
Browsing the World Wide Web is a breeze. Just click on a link or type in a Web-page identifier–the so-called uniform resource locator, or URL. More often than not, the requested page appears on your screen within seconds, downloaded from a computer that could be anywhere in the world.
We owe such reliable, speedy service to a standard set of procedures that governs communication between computers connected to the Internet. Largely invisible to the user, these protocols orchestrate an intricate duet of messages between interacting computers to guarantee that the right page appears in the right place at the right time.