Friday, April 27, 2007

Quantum Cryptography Hacked

Well, so much for the security argument for quantum cryptography. Physicists at MIT has managed to "hack" into a network (limited time open link) protected by quantum encryption.[1]

..... a group from the Massachusetts Institute of Technology (MIT) in Cambridge was able to 'listen in' using a sort of quantum-mechanical wiretap. The trick allowed them to tease out about half of the data, in a way that couldn't be detected by those transmitting or receiving the message.

Still, all is not lost.

To grab the information en-route would require a 'quantum non-demolition box' - a theoretically possible but as-yet-unbuilt device that could measure the photon and pass it along. "What they have done is a simulation of an attack, not a real one," says Lo.

Shapiro and Wong agree. And they add that a quantum cryptographic network can be simply tweaked to beat their attack. By making the key out of a lot of photons instead of just a few, the sender and receiver could ensure that the eavesdropper never got enough of the key to use it. Still, they say, the work shows that secrets — even quantum ones — are never entirely safe.


[1] Kim T., et al. Phys. Rev. A, v.75 p.042327 (2007).

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