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Quantum Cryptography Conquers Noise Problem
ananyo writes "Quantum-encryption systems that encode signals into a series of single photons have so far been unable to piggyback on existing telecommunications lines because they don't stand out from the millions of others in an optical fiber. But now, physicists using a technique for detecting dim light signals have transmitted a quantum key along 90 kilometers of noisy optical fiber. The feat could see quantum cryptography finally enter the mainstream. The researchers developed a detector that picks out photons only if they strike it at a precise instant, calculated on the basis of when the encoded photons were sent. The team's 'self-differentiating' detector activates for 100 picoseconds, every nanosecond. The weak charge triggered by a photon strike in this short interval would not normally stand out, but the detector measures the difference between the signal recorded during one operational cycle and the signal from the preceding cycle — when no matching photon was likely to be detected. This cancels out the background hum. Using this device, the team has transmitted a quantum key along a 90-kilometer fiber, which also carried noisy data at 1 billion bits per second in both directions — a rate typical of a telecommunications fiber."
Where can I get buy my personal quantum crypto kit?
Tomorrow is another day...
In order to send something, the receiver must know when the packet will be sent.
Next thing you know, they'll invent something that will bend light. Oh wait. They already have! It's called a Prism! And next thing you know... hackers will be 'hacking' light by bending it use natural magenetic forces. And cracking that unsafe light transmission, because we all know, light is NOT faster than electrcity....
"transmitted a quantum key along a 90-kilometer fiber, which also carried noisy data at 1 billion bits per second in both directions — a rate typical of a telecommunications fiber."
Telecommunications fiber with a 90km (~50mi.) length would be considered backbone. Typically two fibers are used to send signal in both directions. Single fiber applications require different frequencies of light to both TX & RX. This single fiber application is only used in metro FTTX/GPON situations - never in backbone as the frequency splitting equipment adds relatively high amounts of loss to your signal, impacting how far you can go without regeneration.
...is to get out of your seat, walk across the room and CLOSE THE DARN DOOR like you should have done in the first place..
Why is this shit on my slashdot?
Also notice, 13 comments while the other political junk averages >100.
My understanding is this would allow you to send bits ensured that nobody else had seen them. But every router / repeater must do exactly that, to send them on the next hop. So really, this is just for when you believe you have one continuous fiber strand and want to make sure... correct? If so it does not allow individuals to communicate securely over the Internet, since there is no un-interrupted strand connecting the endpoints. For a truly private network, like connecting missile launch sites to a command center, or helping a domestic telco ensure its undersea hops aren't being spied on by a foreign power between repeaters, then I can see the utility.
Shouldn't it be more like, quantum tamper detection? It's just using one-time pad in such a way that the pad's transmission getting intercepted will trigger the tamper detection mechanism.
"Screw Sun, cross-platform will never work. Let's move on and steal the Java language." - Visual J++ Product Manager
While the hardware challenges are undoubtedly substantial, the basic idea is just a variation on time division multiplexing, which has been extensively used since the days of the telegraph, well before 1900. If this receives a patent, I hope it is for some hardware advance and not just because of the sharing of the fibre.
There are numerous problems:
1. You need _optical_ switches, i.e. switched circuits. That approach failed a long time ago. Anybody remember ATM?
2. 90km is nothing. Amplification is impossible, so unless they reach 10'000km, this is completely irrelevant.
3. Nobody needs it. Cryptography does fine. (No, this is at best "quantum modulation", no crypto involved.) If you are paranoid, use OTPs. They are far, far cheaper, far, far more reliable and completely compatible with existing networks.
4. Remember, this is only key exchange, not actual data transmission. As such it is pretty useless, as you still need to rely on cryptography for the message transfer.
5. The security guarantees are far, far weaker than people are made to believe. Just look at the history of successful compromises.
6. Not even the physics may work out. Quantum theory is a _theory_, not established fact.
Another worthless stunt.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
I gotta admit that I'm not familiar with photonic quantum cryptography.
As far as I know, photonics means light, and light does reflect - and could even possibly be diverted (from one beam and splits it into two)
Can the MIM (man in the middle) spit a beam into two, letting the "original" beam to travel to whoever the recipient while working on the "branch"?
Would that approach cause a "noticeable disruption"?
Muchas Gracias, Señor Edward Snowden !
If you read the paper (which you can do even as a computer scientist like me), you'll note that they didn't use time- but frequency division. The hardware challenge was how to deal with noise from that regular data spectrum. While an impressive solution by itself, I'm more worried about this part of the abstract of their paper:
Quantum key distribution (QKD) uniquely allows the distribution of cryptographic keys with security verified by quantum mechanical limits. Both protocol execution and subsequent applications require the assistance of classical data communication channels. While using separate fibers is one option, it is economically more viable if data and quantum signals are simultaneously transmitted through a single fiber. However, noise-photon contamination arising from the intense data signal has severely restricted both the QKD distances and secure key rates. Here, we exploit a novel temporal-filtering effect for noise-photon rejection. This allows high-bit-rate QKD over fibers up to 90 km in length and populated with error-free bidirectional Gb/s data communications. With a high-bit rate and range sufficient for important information infrastructures, such as smart cities and 10-Gbit Ethernet, QKD is a significant step closer toward wide-scale deployment in fiber networks.
Based on their figure 2c (and text), this should be possible when transmitting sufficiently loudly. However, I'm confused as to why this does not affect noise in their own channel. Or maybe that's why they're claiming it... but I don't know enough about fiber optics to draw a conclusion there.
In any case, this technology is rather hard to use, because it only works in fibers over a single hop. So you could in some cases create secure key exchange between two hops. Which, to be fair, is a great achievement: however, there is no wireless and there is no support for switching. So you'd need an IPSec-like protocol on the MAC layer for this to work; however, this means replacing every single switch on the path.
Supposing I didn't get the message I was expecting to receive, how do I know it wasn't intercepted?
I still don't understand the benefit of Quantum Cryptography - it only prevents eavesdropping on the wire, right? It doesn't prevent a man-in-the-middle (where someone would receive the signal, read it, and retransmit it along the wire)?
Assuming your machine is clean from infection, the big eavesdropping concerns today come from man-in-the-middle attacks: rerouted lan traffic (such as compromised clients running an ARP spoof), and intermediary nodes between endpoints (eg. your ISP, and the Internet backbone routers). The only thing QC prevents (actual, physical wiretapping), as I understand it, is not much of a concern anyways.