Twenty years ago, North American physicists Giles Brassard and Charles Bennett outlined a way to send a key without anyone being able to eavesdrop. Their idea rests on the notion that a message sent using quantum particles -such as photons - is so fragile that measuring the photons changes their properties. So anybody listening in to a transmission would destroy it - which the sender and receiver would easily notice.
But so-called quantum encryption works only if the key is sent using individual photons, rather than the pulses of many photons that are used for communication today. But sending single photons is tricky.
In the last year, a number of companies have begun selling quantum encryption kits that create single photons by reducing the intensity of a laser beam so that it produces pulses each containing less than one photon, on average. But there always remains a small probability that any pulse will contain two or more photons.
This is a potentially serious weakness because a hacker could intercept the extra photons without the sender and receiver being any the wiser.
Lasam ieksh:
New ScientistCurrent Music: Bob Marley - Zimbabwe |
![[info]](http://klab.lv/img/userinfo.gif){kind=small}
