"Each key is usually extra-encrypted, but documents disclosed by former National Security Agency contractor Edward Snowden in 2013 showed that the U.S. government, which hoovers up most of the world’s internet traffic, can also break those tougher codes. Exactly how the NSA accomplishes this isn’t widely known. (One suspicion is that while keys are supposed to be based on multiplying two random large prime numbers together, many systems use a relatively small subset of primes, making it much easier for a computer to guess the key.)"<p>Sorry, what a load of bullshit...
> If any of the pulses’ paths are interrupted and they don’t arrive at the endpoint at the expected nanosecond, the sender and receiver know their communication has been compromised.<p>This isn't how QKD works - it isn't based on timing or delays. The common BB84 protocol (and the decoy-state modification) are based on the fact that measuring a photon necessarily changes it. Essentially, it is easy to distinguish a photon that's been measured twice from a photon that's been measured once (statistically speaking). Because an eavesdropper would <i>necessarily</i> have to measure photons in order to extract any useful information about the communication, their presence can be easily detected.
"Yet for high-speed transmissions under real-world conditions, the record is just 60 miles. Farther transmissions require a series of “trusted nodes,” relays that are themselves vulnerable to hackers or physical tapping. China uses armed guards to secure the nodes in its 1,240-mile QKD network"<p>Armed guards at the relays.. I wonder what they are transmitting on that cable. In any case it seems they take the thread of fiber tapping very seriously. I bet the US government have similar experiments only they don't talk about it.
I still don’t understand the point of quantum key distribution. It protects against passive snooping but not against an active man-in-the-middle attack: thus it gives you no more protection than, say, the Diffie-Hellman exchange performed at the start of every TLS connection. The main counterargument is that quantum computers can break Diffie-Hellman, and can do so retroactively if someone is tapping your communications today and saving them for the future. But post-quantum public key cryptography exists; admittedly it’s not as vetted yet as the traditional kind. but it will be soon enough, so even if there’s some rationale for using QKD today, it’s not the “future-looking” technology it’s sold as.<p>And in the meantime, if you really want to guarantee the confidentiality of your shared secret that badly, you can just physically drive over to the other organization carrying a copy of it. Inconvenient, but surely less so than running long fiber-optic cables through tunnels solely for that purpose.
>showed that the U.S. government, which hoovers up most of the world’s internet traffic, can also break those tougher codes<p>There's a lot the NSA hasn't broken. Why not just use higher block sizes like RSA-2048 or large DHE parameters instead of a quantum network?
> ...fire data in weak pulses of light, each just a little bigger than a single photon. If any of the pulses’ paths are interrupted...<p>We are living in the future already.
Interesting. Here in The Netherlands there will be a quantum network connecting Delft, The Hague, Leiden and Amsterdam, but that's largely still a research project and it won't be up and running before 2020. If QuantumXC has commercially available tech then they seem to be ahead by a couple of years.
What I see when I tap the link on mobile:<p>1. Huge ad at the top.<p>2. Large persistent bar under that telling me I’m on Bloomburg’s Site.<p>3. Headline in large bold font.<p>4. Author and dateline<p>5. Huge blue (sharing?) icon with white dots<p>6. Huge persistent bar begging me to log in or subscribe.<p>7. Large persistent ad at the bottom.<p>After much scrolling you can get to the article. The state of mobile web journalism I guess.
> fire data in weak pulses of light, each just a little bigger than a single photon.<p>so the stream can't be split because the bits are so small?