Researchers at the University of Toronto have developed a new technique using photons to keep your data safe when transmitted over a fiber-optic cable. They based their research on Heisenberg's Uncertainty Principle and used photonic 'decoys' to encrypt data over distances of 15 kilometers. By mixing these photon keys with the data during a first message and separately sending another one telling the receiver which photons carried the signal and which were decoys, they're sure to catch any eavedroppers. This technique could soon be used for online banking as the scientists think it could be effective up to 100 kilometers.
Let's start with two short paragraphs from the University of Toronto news release.
For governments and corporations in the business of transmitting sensitive data such as banking records or personal information over fibre optic cables, a new system demonstrated by University of Toronto researchers offers the protective equivalent of a fire-breathing dragon.
"Quantum cryptography is trying to make all transmissions secure, so this could be very useful for online banking, for example," says Professor Hoi-Kwong Lo, an expert in physics and electrical and computer engineering at U of T’s Center for Quantum Information and Quantum Control. "The idea can be implemented now, because we actually did the experiment with a commercial device."
The Toronto Star provided more details in "Prof says there's no hacker he can't foil."
"We are using fundamental quantum mechanics principles that no eavesdropper can do anything about," says Lo. "We can use this to confuse the eavesdropper, and severely limit what he can do," adds Lo. "The principle is that if someone makes some measurement, or has some interaction (with the protecting photon), then its quantum state will change."
Please read this article to discover what happens in this particular scenario to the usual suspects in quantum cryptography: Alice and Bob exchanging a message, Eve trying to intercept it.
But will this new encryption technique be useful?
While the theoretical use of photons to encrypt information is not new, Lo's study showed that it can actually work at commercially viable levels and that long strings of information can actually be transmitted.
Until recently, it was thought that such information couldn't be transferred more than 8 kilometres. But Lo's laser modulation technique increased that to 60 to 100 kilometres.
"We have proved that it can actually work in practice," in a way that's commercially viable, he says.
For more information, this research work has been published by Physical Review Letters under the title "Experimental Quantum Key Distribution with Decoy States" (Volume 96, Number 7, Article 070502, Published on February 22, 2006). Here is a link to the abstract.
To increase dramatically the distance and the secure key generation rate of quantum key distribution (QKD), the idea of quantum decoys—signals of different intensities—has recently been proposed. Here, we present the first experimental implementation of decoy state QKD. By making simple modifications to a commercial quantum key distribution system, we show that a secure key generation rate of 165 bit/s, which is 1/4 of the theoretical limit, can be obtained over 15 km of a telecommunication fiber. We also show that with the same experimental parameters, not even a single bit of secure key can be extracted with a non-decoy-state protocol. Compared to building single photon sources, decoy state QKD is a much simpler method for increasing the distance and key generation rate of unconditionally secure QKD.
And in the same issue of Physical Review Letters, you'll find another article co-signed by Hoi-Kwong Loon a related subject, "Quantum Key Distribution Based on Arbitrarily Weak Distillable Entangled States" (Article 070501, Published on February 21, 2006). Here is a link to the abstract of this other paper.
Sources: Nicolle Wahl, University of Toronto news release, February 22, 2006; Joseph Hall, The Toronto Star, February 23, 2006; and various web sites
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