Encryption keys sent by invisible light

Boffins in the British military have improved the technique for sending encryption keys on a secure satellite transmission.

According to the journal Nature, researchers at QinetiQ, which prior to its spin off was part of Britain's defence research lab, have successfully exchanged encryption keys transmitted on a beam of invisible light.

The researchers completed the exchange from two mountaintops in southern Germany 14 miles apart.

Within seven years, the technique ought to be able to transmit encryption keys to any receiving point on the planet via low-orbiting satellites, said a QinetiQ spokesman.

Encryption technology currently uses mathematical 'keys' which are exchanged between trusting users. The keys are used to unscramble messages, video and other data.

But such keys can be intercepted on conventional networks and have to be sent by motorbike couriers or in diplomatic bags.

The boffins at QinetiQ believe that keys can be exchanged more reliably by attaching the key's digits to individual light particles, or photons, which are sent as a weak beam of light.

The practice is believed to be safe because intercepting and reading the key noticeably alters the state of the photons, tipping off the intended recipient that the key has been compromised.

However, the scientists say that this "quantum cryptography" would require the construction and launch of new low-orbit satellites.