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Ultrasecure Quantum Communications Over Thin Air
SlashDotIDOne writes "Well, given a hundred years at university and a few extra titles to my name, I'd be comfortable trying to summarize the article so don't take what I say at face value. Apparently British and German researchers have found a way to use quantum crypto through the air, thus allowing it to be used to communicate with satellites, etc. A very secure form since you know whether a message was intercepted, rather hard to tamper with ;). Courtesy India times and Google's new news service."
First, I'd like to point out that quantum computation and quantum encryption are two almost completely separate concepts. Quantum encryption is based on the fact that quantum states cannot be measured without altering. The most common example is the polarization of a photon, but it will work for any quantum state, so long as there exist, effectively, two unique states that can transmit the data.
Quantum computation, however, is much more complex and much more interesting. Quantum computers are based on the concept of quantum entanglement, the ability of a quantum state to exist in a superposition of all of its mutually exclusive states: It's a 1 and a 0. However, this is not as easy to use as one might think. While it's true that if you have n quantum logic gates you have the ability to input 2^n data values simultaneously (as opposed to only 1 piece of data if you have n digital logic gates), this is not going to be the end of classical computing for a few reasons. First, quantum computers have to be perfectly reversible. That means for every output there's an input and vice versa. And there has to be no way of knowing the initial states of the data. You don't process data, you process probabilities in a quantum computer; if you know exactly what any one value is throughout the computation, you can find out all of the values: the superposition ends and you're stuck with a useless chunk of machinery. This means YOU CAN ONLY GET ONE RESULT FROM ANY QUANTUM COMPUTATION, THE END RESULT. You can't see what the data in the middle is or the computer becomes useless. (Landauer's principle makes heat loss data loss. When your processor gets hot, it's losing data. If the same thing happened to a quantum computer, it wouldn't be quantum anymore.) Decoherence is what happens when you randomly lose data to the environment by design, not by choice, and the superposition ends. This is bad for Q.C. Oh, and quantum computers can only do *some* things faster, like prime factorization and discrete logarithms. Not multiplication or addition. Plus, the circuits that would do basic arithmetic would be bigger and slower than what you've currently got.
So what does this all mean? It means that quantum computers are going to provide some advantages (real quick big number factorization), and some disadvantages (that whole RSA standard). The most realistic initial use of quantum computers will be as add-ons to existing super-computers to resolve certain types of NP-Complete headaches that regular math can't simplify yet. At best they will someday be an add-on to your PC; but they will never replace the digital computer.~
If you want more info, check out http://www.qubit.org, it's got some decent tutorials.
You're missing the point. Quantum cryptography had been done before, but only over fibreoptic cables. This is the first time it has been done through air, which opens up lots of new possibilities.
Yeah, but it's nice to reduce the problem to endpoint security, because (a) you're always going to need endpoint security (so it's nice to be able to focus on it exclusively) and (b) endpoint security problems haven't changed fundamentally in the past few million years or so: you keep bad people away from the endpoint and, if necessary, induce sufficiently people to work for you with sufficient motivation that they are sufficiently hard to bribe or threaten.
If you're going to create something for the government its inherantly going to fall into the hands of civilians.
Our arguably most complex technology is the atom bomb but every highschool student with half a brain knows the basics of how a nuclear reaction works.
This isnt really a problem for us because regulation of these components is a relatively easy job. Its not like joe-terrorist can go mine his own plutonium or deuterium or uranium (the makings of most nuclear devices) though there are others.
smoke detectors contain valadium etc and as in a previous slashdot artical can be turned into nuclear devices. (remember the kid in his garden shed)
So back to the real point, how do the creators of this technology (read information) keep it secret. After all information wants to be free. Poloticians screw up interns leak data and university professors love to defeat these kind of things.
So if you're going to create it, you better be sure you want every one to have it. Which is incidently for the same reasons that the guy who created the atom bomb(well theory) is quoted as saying (paraphrased) that he never should have created it dispite the good that has come from nuclear energy.
--Editorial-- (well moreso)
I think that this technology should be created etc. But created for the public domain. Security and privacy are what good countrys are founded on. Through corruption and "wont someone please think of the children" we've given up this freedom peice by peice to the governments that represent men with money. (read riaa)
What then is the next logical step? i say declare war on privacy invasion; since the government isnt run for the people any more it must be business that impliments privacy for the people.
quantum state encryption will finally give people the ability to have a discussion in private. Is the fact that joe is cheating on his wife any more important than saddam having an abomb to joe? what if both were found out. with quantum tech this doesnt seem possible YET.
(alright its a spacious argument but blah)
so now that i sound like a madman i await your flames. encryption doesnt make a person a terrorist and good people have a right to privacy. the argument that if you dont have anything to hide you dont need encryption doesnt hold water. ANY information intended for one party should not be received by another.
I had a student do a project on this. You can live with quite high levels of photon loss.
Essentially, the process runs:
send a large number of (more-or-less) single photon pulses, carrying random data
recipient reports over an open channel, which pulses they got and some more technical information.
From this, sender and recipient can work out the subset of the random data that they take into the next step.
Now they (openly) exchange some checksums and things to determine the rate of bits which appear to have changed in transit, either due to eavesdropping, or noise and to get a common bitstring. From this, they can work out how to combine the bits of the bitstring to get a shorter bitstring which (with high probability) no eavesdropper can guess any part of.
Finally, they use this common secret bitstring as a key for a one-time pad.
Simulations suggest that even 99.9% photon loss is not fatal.
A very secure form since you know whether a message was intercepted, rather hard to tamper with ;).
I'm not sure how knowing if a message has been intercepted makes it more secure. I can yell to a friend across a crowded room, and when people turn their heads at the sound of my voice, I know my message has been intercepted. Does that make it more secure?
It's doubtful based on the reports that the US will allow such a thing to pass unless they can intercept and read it.
Does anyone else think it would be a great addition to Slashdot's stories if they would include a link to the google news search under every headline? I don't think it would be that hard to automate, but it sure would open the door for us users to see a lot of different articles per issue discussed.
~ now you know
WMOB The recordings and transcripts (that you REALLY need) of some gangsters wiretapped by the FBI.
Its awesome!
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