Cryptography has had a long and distinguished history of military and diplomatic use dating back to the ancient Greeks. But secure communications are becoming increasingly important for commercial applications as well. In 1986, for instance, a satellite television broadcast in the US was interrupted by a message from a hacker known as "Captain Midnight". The incident highlighted how easy it was for an unauthorized party to gain control of a satellite system, and sparked a massive criminal investigation. It also motivated researchers to find new ways of ensuring that messages transmitted to and from satellites remain secret.