Please correct me if I'm wrong in these statements:
This seems to be a medium dependent security method. It seems to rely on the physical properties of light, by its nature. It's not an encryption method (such as could be transmitted over any medium (copper wire, paper documents, radio signals, etc)), so much as it is a secure data transmission method. Besides, clear text can be sent if you have a secure medium... If I have 2 computers connected by serial cable inside my house, and I am the only person with physical access to them and the cable, I don't need encryption at all. What this article seems to be talking about is just a way of making sure no one intercepts the data stream without detection... (this is quite different from standard encryption, which assumes that the attacker has full access to the data stream.)
It sounds to me like they're using their secure link to transmit a key. But to even call it "unbreakable", they would need to use a key as big as the message (one time pad). If the physical link is so secure, why not just send the clear text and not bother with a key? If the key is smaller than the message, then it is not unbreakable.
I can see that it might have a practical application for banks or other institutions that need to transmit large amounts of secret data between fixed points, but it seems impractical for most other uses (such as secure internet browsing).
It seems that, still, the only truly unbreakable encryption is the random one time pad.
P.S. The top article in the "See Also" section
seems to confirm that it is a means of sending conventional (breakable) keys over a secure medium. I don't see how the more recent article can justify calling it "unbreakable".
P.S. From one of the other "See Also" articles:
So they mean it as an alternative to that... I had previously been thinking they meant it as an alternative to public (asymmetric) key cryptography, which is currently used, in applications like web browsing, to exchange symmetric keys. But they mean it for higher stakes stuff, like government stuff, where using public key cryptography would not be good enough. But still, standard symmetric key encryption is breakable..."At the moment, highly secure encryption keys are typically sent by a man on a motorbike or a guy with a diplomatic bag," said John Rarity, a scientist with QinetiQ.
Another "See Also" link:
Again, it's a secure way of swapping breakable keys... Really, it should be advertised as a secure (to the best of our knowledge), medium range physical link, not "unbreakable encryption".Encryption usually involves scrambling data with long numeric keys that stop other people reading it.
The information inside the message is effectively kept secure because of the time it would take an eavesdropper to sort through all possible keys used to scramble the data.
But quantum cryptography scrambles data in a different way by using the strange properties of the quantum world to guarantee that keys have been swapped securely.