In-Depth

Quantum Cryptography Offers Uncrackable Keys

Using the laws of physics, not mathematical difficulty, to secure data, MagiQ Technologies' Navajo Security Gateway offers "future-proof, unbreakable" security devices.

• By Mathew Schwartz
• 11/19/2003

MagiQ Technologies CEO Bob Gelfond sat down with Security Strategies to explain how the system works, and how it avoids the problems of today's key distribution technology.

What is quantum cryptography?

This is a cliché, but it really is a paradigm shift in the way people approach security. Up until now, data encryption has really relied upon the relative security of mathematical complexity—not the fact that a problem is impossible to crack, but that it would take millions of years. A lot of the key distribution systems are also based on mathematical algorithms.

How is quantum cryptography different from mathematically based encryption?

Instead of relying on mathematical difficulty, we’re actually using the laws of physics to guarantee authenticity. We can work with any encryption algorithm that someone wants to work with, the problem is that even if you have a really good encryption algorithm, if someone gets their hands on the key, all bets are off. So we’re improving the key distribution [scheme]. We ship with AES [Advanced Encryption Standard] or Triple-DES [Data Encryption Standard], or if someone like the NSA wants to put in their own algorithms, [it can].

How does it improve key distribution?

It’s impossible to read the key, it’s impossible to break the key. Once the key has been exchanged between point A and point B, the only thing someone can do is attack the box. But if someone tries to take a screwdriver and open one of the boxes, the keys are going to zero out, because the box is tamper-proofed. Even if it was possible for someone to get a copy of the key, the keys are changing at the rate of about once per second. So it wouldn’t do them any good.

How does this improve on key distribution today?

The problem now in many environments is that people are sending keys from point A to point B, where they load the key onto a box, then ship the box out, which is problem because it gets touched by a lot of hands. The other [approach] is where a guy with a briefcase handcuffed to his wrist goes from one place to another. Unbeknownst to him, though, it’s still possible to copy that key digitally. So it creates another loophole.

That’s not enough?

There are two problems [today with key use]. First, in large networks, to regenerate the key, you have to take the system down. We talked to a large technology company, at one of the biggest [telecommunications companies] in the world, and the network administrator said, I could change my key but I don’t want to take my network down. In practice, he hadn’t changed the key in four years. If you don’t, it makes it a lot easier for someone to get access to that data.

What’s the other problem with today’s keys?

The more times that you reuse a key, you introduce patterns into the data, so now with AES—which in theory should take a million years to break, depending upon how often you repeat use of that key—the brute force attack difficulty can come down dramatically. We know this is going on, we hear stories from telecom operators that they find taps on their lines all the time. There was an article in Barron’s a year ago; Boeing said they had encrypted data on a new plane design stolen, and the data was believed to have been stolen by French intelligence on behalf of Airbus. Navajo would be able to prevent those kinds of things.

How might this be deployed?

There’s interest from biotech, high-tech, even tire manufacturers—it’s an industry that spends a lot on materials and R&D. It’s very competitive; there is a lot of corporate espionage. Or Toyota is another example. They have R&D at one site, manufacturing at another, and they have to transmit that information and are very concerned that [someone could eavesdrop].

How difficult is it to tap a network?

Optical fiber is very easy to tap, for a few hundred dollars you can get a very simple tap. It’s much easier to tap fiber than people realize. We talked to a large international bank in Manhattan, and they were using a private line to send data from their main office in Manhattan to a disaster recovery site in New Jersey, and they weren’t encrypting their data. It’s vulnerable.

Where do Navajo boxes sit in the network?

You need a Navajo box at each site. Our boxes can be as far as 120 kilometers apart—right now that’s the limit. Over time, as with any other technology … each succeeding generation will have more [range], and become cheaper too.

How does it work?

Quantum information is the most sensitive things known in the world, so it’s impossible to interact with that information without changing it. Just the act of reading it, measuring it, touching it, changes it. [When that happens] we can pick it up instantaneously, and see then the photons are bad, so to speak. Then … it’s up to the user what to do. The units are highly configurable—who to send alarms to, whether to shut down.

How does it use photons?

Single photons are created by weakly attenuated light. Essentially, it’s very low-level light, and as you turn the level down on the light—the laser—you get a statistical probability of creating a single photon, and then we put the single photon in a super position, and that embeds it with quantum information.

How does the sending box work?

The sending box has to make two choices, and it makes those with two true-random-number generators—and these are true random numbers. So the two choices are one or zero, as with any other bit, and then which polarization basis in which to send the information—you can send it in a diagonal basis, or the horizontal/vertical basis. The receiver has no way of knowing which configuration the photon was sent in. Then … the receiver makes a public announcement, he says which [configuration the received proton] is in, and the sender says you’re right, keep the photon, or you’re wrong, throw it away. The … box actually sends more photons, because some will have to be sacrificed to do an error check. So the receiver says … okay, you got a 1 percent error rate, that’s below the threshold for someone listening … so you [are secure].

How often do the boxes generate keys?

You’re constantly generating key material. You have one channel, the quantum channel, doing key distribution. The data channel is independent. In practice, we can do up to 1 gigabit Ethernet. We’ll be coming out next year with a way to go up to OC-192—10 gigabit Ethernet. But … the data is independent, that’s where we’re doing standard encryption. This is really marrying quantum key distribution with classical cryptography.

So there’s the data channel; how does the quantum channel work?

The quantum channel is building up the key. The data that you’re encrypting, you know that you have a safe key with which to encrypt the data, but you constantly have to refresh that buffer of keys that’s inside the box. The key is refreshed once per second … there’s enough buffer that you have enough keys.

Is that rate more frequent than normal with encryption?

DES is probably flipping it once per week.

What’s the physical requirement for the quantum channel?

The only requirement is that we need a dark fiber to run the quantum channel, and it has to be a point-to-point connection, 120 kilometers or less, and we’re assuming that the boxes are in secure locations themselves.

So Navajo detects something, maybe someone listening in; what happens next?

What likely happens is the data continues on, because you’re sending the data encrypted, and you’re sending buffered, secure keys. So you could continue your data [stream] … while you’re investigating the problem. Because you don’t want to shut the system down every time there’s a problem—it’s too cumbersome. We really spent a lot of time making this practical. That’s where a lot of value-add comes from, in terms of being used by the average customer. This is a complete, robust, commercial system, it’s not something you need a dedicated physicist or engineer to baby sit. It’s just one more reliable Internet appliance that you have, fits in a standard rack, you plug it in, and it works, it’s reliable 24/7/365, and that’s a big advance over what’s been out there.

Can companies use this for public key infrastructure?

They can, and certainly the key management is much simpler now. This guarantees keys are random, which you don’t always have in software solutions. [These keys are] impossible to copy or read, and you can know for sure the only copies of those keys reside inside the Navajo boxes, so data that you’re sending, if you have a multi-site network, regardless of where the data is flowing, you’re safe because your keys are safe. And you’re able to flip your keys very frequently. Those are the two vulnerabilities of current systems. It’s important that we’re not saying that AES or Triple-DES are vulnerable, because today they’re not, but they’re mathematical algorithms, so in the future … maybe someone [will break them more easily].