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6 Details about Quantum Encryption at LANL

In a paper on arXiv[1], a team of researchers at Los Alamos National Laboratory revealed that they had been successfully using a quantum encrypted network for the last two and a half years.

It’s pretty cool stuff, although not as cool as it might sound.  What follows are a few details of the technology including what it will and won’t do.

1.  It’s not fully networked technology
The system works on a client/hub architecture.  While all clients have quantum enabled transmitters only the hub has a quantum enabled receiver.  While the quantum transmitters can be made rather small and scaled for manufacturing, not so much for the receivers which require moderate cooling.  The transmitter is pretty classy looking and is shown in picture 1 below.

2.  It’s not fully quantum encrypted
At least one other reader and myself were confused by the MIT review[3] of the article that used the term ‘one time pad’.  I suspect we’d had just enough crypto exposure to confuse ourselves, but in case you’re in the same boat, here goes.  If ‘one time pad’ means, to you, a pad of random numbers that’s xor’ed with the transmitted message and somehow also transmitted securely to the destination of the message where it will be used once to decode the message and then discarded providing Shannon perfect encryption, then no, that’s not what the LANL paper details.  Basically the scheme uses quantum encryption to encode the keys that are to be used for the bulk message that will be transmitted via standard non-quantum algorithms.  Quantum encryption is used only for the key exchange portion of the message in the same manner that RSA is used in current TLS/SSL technologies.

3.  Your bulk message is still vulnerable to a brute force attack on the non-quantum algorithm
See number two.  Whatever sort of brute force attack an interloper could use on standard algorithms without knowledge of your key can still be used.  This is slightly more assiduous than it seems.  It depends on a number of things like message redundancy.  I can’t find the reference, so I won’t quote the algorithm used, but an engineer in the ’80s showed that a rather secure algortihm could be broken quite easily if it was used to encode auido recorded voice signals.

4.  Your key is completely secure and can’t even be monitored for a brute force attack!
What it does encrypt, the system encrypts very, very nicely.  One of the key advantages of quantum encryption is that the bit stream can’t even be monitored.  If you measure it, you destroy it.

5.  I may have worked for one of the researcher’s dads.
Said in the tone of New York taxi drivers who are commonly portrayed as always saying ‘Seen it.’, no matter how absurd the situation.  (If you’ve seen Curious George, you’ll understand.)  I actually may have worked for Kevin McCabe’s dad when I was an intern in the electronics shop at Los Alamos.  Kinda inconsequential, yet kinda cool to me :)  Checking on it.

6.  Finally, the system is still vulnerable to the most obvious attack of all[2]

References:

1.  ArXiv paper
http://arxiv.org/abs/1305.0305

2.  xkcd on crypto
http://xkcd.com/538/ 

3.  MIT Review
http://www.technologyreview.com/view/514581/government-lab-reveals-quantum-internet-operated-continuously-for-over-two-years/

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