Broadcast Quantum Crypto

Quantum cryptography, a technique of producing secret messages that are reputedly uncrackable, may soon be used by orbiting communications satellites thanks to experiments by British and German researchers.The traditional weakness of sending encoded messages is eavesdropping. Quantum cryptography gets around this by sending an encoded message and, separately, a key to decode it, which are transmitted in pulses of individual light particles called photons.By the nature of quantum mechanics, if a single photon is intercepted en route, that changes the state of the information package as it arrives at the other end.That is a telltale for the legitimate recipient that his message has been tampered with -- the same as if someone received a letter that had been clumsily opened and then resealed, leaving traces of glue and fingerprints on the envelope.
http://timesofindia.indiatimes.com/cms.dll/articleshow?art_id=23998757