The Global Positioning System is available for anyone in the world to use free of charge. You’d think that would be a pretty good deal for everyone, but the Europeans decided to build their own competing system. They promised to follow the American example and make the decryption codes “open source”. But after the new system began operating in January 2006, the Europeans changed their minds. The decryption codes are secret, and you have to pay a fee for access.

A group of GPS geeks at Cornell University thought that was a shoddy thing to do. So they decided to crack the codes and publish them.