How To Build a Quantum Eavesdropper

KentuckyFC writes "Quantum encryption is perfectly secure, in theory. In practice, however, there are loopholes. Now Japanese scientists have designed a quantum eavesdropper that exploits one of these loopholes to listen in to quantum conversations. QC's security arises from the impossibility of making a perfect copy of a quantum object without destroying it — so the sender and receiver can always tell if they've been overheard. But it turns out that an eavesdropper can make imperfect copies and use them to extract information from a quantum message without alerting sender or receiver (abstract). The Japanese design does just this. That should worry banks and government agencies that have begun to use some of the commercial quantum encryption systems now available."

Comments

Ob. LOTR

[HungSoLow]

I've been droppin' no eaves sir.

You fool!

[scipiodog]

By listening in with the Quantum eavesdropper, you've changed what they were actually saying!

No need to worry about this

[QuantumV]

But it turns out that an eavesdropper can make imperfect copies and use them to extract information from a quantum message without alerting sender or receiver (abstract). The Japanese design does just this.

This is wrong. The eavesdropper gets imperfect copies and so does the receiver. If the quality of the receiver's copies are as bad as the eavesdropper's, any working quantum crypto setup will abort and not try to make a secret key out of it.

That should worry banks and government agencies that have begun to use some of the commercial quantum encryption systems now available.

Nobody needs to worry about these kinds of attacks, as the software in all commercial quantum crypto systems automatically checks and takes care of these kinds of attacks. What the paper shows is how to implement in practice a class of attacks that has been known for years how to do in theory.

There are other attacks on quantum crypto systems that actually attack loopholes in the implementation, and some of these have previously been discussed on slashdot here