Secure quantum networks over regular fiber are coming.

A new kind of data network is on its way that will immediately, and in real-time expose attempts at interception, engineers say. But that’s not all, what’s fascinating about it is that not only does the network identify a hack-attempt in absolute real-time, but it scrambles the data traffic so that any perpetrator can’t see stolen material anyway.

The security technique is called quantum key distribution (QKD), and it can be run over standard fiber cables. Successful field tests were just announced of a variant of it, by Chinese researchers publishing their work in a Quantum Science and Technology, an academic journal. 

QKD is un-hackable many scientists think. The main reason is that because the cryptographic keys, which are made up of subatomic light particles, are so inexorably linked, any tampering immediately declares itself. The attempted infiltration into the regular data is detected because the encryption particles, in this case, photons, aren’t conjoined anymore as they should be. 

Interestingly, the meddling shows up all along the link. So not just at the beginning or end nodes. And, as a bonus, not only are network managers thus notified as the attempt occurs but at the first sign of trouble, the keys are automatically canceled and no one ever sees the data.

Real tests

The Chinese group, a collaboration between researchers at Peking University and Beijing University of Posts and Telecommunication, say that their version of QKD, Continuous Variable QKD, or CV-QKD ran over 30 miles on a standard, commercial fiber link in Xi’an and Guangzhou. They say their system is better than other QKD networking because it runs on standard telco equipment and at room temperature.

The Chinese test isn’t the first QKD-secured network. There have been others, including some commercial launches. UK telecommunications provider BT, in 2018, said it had completed a 75-mile QKD-secured fiber link there. It’s “virtually un-hackable,” Gavin Patterson, BT’s then chief executive said at an expo I attended there around that time.

That BT link is between a university and the giant telco’s research lab. “It provides a further layer of security for personal and sensitive data, over and above the standard methods used by banks and credit card companies,” Andrew Lord, BT’s chief of optical network research and development, says on the company’s website.

Thwarting the hacker

Lord explains, in more detail, that’s it’s the attempt to grab the encryption key that’s being sent that muddles the key. It “introduces errors to their encoding,” he says. That makes it strikingly apparent when a hack is attempted—the entangled key no longer works. The transaction is then halted, and a new key is “sent automatically.”

There’s still work to do overall, however. One problem with QKD-secured fiber, just like standard light, in fact, is that the photons that make up a quantum key network can’t go down pipes at the same strength forever—they shine less-bright over distance, and scatter, eventually disappearing. 

The puzzle is that adding repeater nodes to amplify the signal adds insecurity. At Aquila, we’re always evaluating threats and proposing solutions, drop us a line to learn more.

Pat Nelson
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