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Single-Photon LED: Key To Uncrackable Encryption?
nut writes: "The BBC are carrying this story of new type of LED so precise that it can emit just one photon of light each time it is switched on. It has been developed by scientists from Toshiba Research Limited and the University of Cambridge. It is described in the journal Science, although I can find no mention of it on their website. One of the applications of this is supposedly uncrackable encryption, due to the law of indeterminacy. This application is described fully in 'The Code Book', by Simon Singh, although the method was only theoretical at the time the book was first published."
And as far as I can tell, this is only a silly little theory. So far they've figured out how to emit one photon, but they don't know how to read it. I'm sure that this is gonna be HUGE...
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The line can't be tapped, because if you intercept the photons, you can't re-create the signal. Read an article on Quatum Cryptography.
-Mark
Man, I wish we could just set our nation's resource distribution slider to 100% for technology for, like, a week. Then we'd have all this great new tech to mess around with!
Of course, we'd have to switch the slider back to 100% social for a couple weeks to quell the riots that resulted in a week of no police, social services, or law. But... nifty new toys!
"Destroy science and religion. Science would re-emerge exactly the same; but not religion." - Penn Jillette, paraphrased
I've been following this technology with great interest. There seems to be a fundamental problem: it is point to point. Its applications will be fairly limited.
It seems to me, at least in terms of networks, that this would really be used to secure lines between networks, clusters, or individual computers. But on today's public Internet, this isn't really an issue. Of course, I would rather use this technology than to not have lines protected with quantum indeterminism.
Most security people are more concerned about platform security than link security. If this technology can be used to reinforce something used for platform security, then boo yeah! Otherwise, this is cool, but I'm not going to get a heart condition over it.
The only platform benefit I see is reducing the need to perform expensive computations to encrypt and decrypt data. Let the link take care of that and thus increase performance. Of course, how many nodes on the Internet only want to talk to their nearest neighbor? And how many routers and such are between them and their nearest neighbor? It might not even be possible to secure the link between a node and its nearest neighbor in most cases.
I doubt this technology will impact current Internet infrastructure all that much. We'll see.
Here's the Science Magazine Abstract
----Abstract-----
Electrically Driven Single Photon Source
Zhiliang Yuan 1, Beata E. Kardynal 1, R. Mark Stevenson 1, Andrew J. Shields 1,Charlene J. Lobo 2, Ken Cooper 2, Neil S. Beattie 3, David A. Ritchie 2, Michael Pepper 3
1 Toshiba Research Europe Limited, Cambridge Research Laboratory, 260 Cambridge Science Park, Milton Road, Cambridge, CB4 0WE, UK.
2 Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge, CB3 0HE, UK.
3 Toshiba Research Europe Limited, Cambridge Research Laboratory, 260 Cambridge Science Park, Milton Road, Cambridge, CB4 0WE, UK; Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge, CB3 0HE, UK.
Electroluminescence from a single quantum dot within the intrinsic region of a p-i-n junction is demonstrated to act as an electrically driven single photon source. At low injection currents the dot electroluminescence spectrum reveals a single sharp line due to exciton recombination, while another line due to the biexciton emerges at higher current. The second order correlation function of the diode displays anti-bunching under a DC drive current. Single photon emission is stimulated using sub-nanosecond voltage pulses. These results suggest that semiconductor technology can be used to mass-produce a single photon source for applications in quantum information technology.
-----End Abstract-----
If anyone has access to Science Online (http://www.sciencemag.org) you can download the PDF reprint at this link: here.
"One touch of Darwin makes the whole world kin." George Bernard Shaw
The application refers to its use in quantum cryptography. It doesn't render the encryption process uncrackable, but makes it able to detect that someone is eavesdropping and/or has broken the encryption. With current methods, you can't tell if someone has broken your key and read your message. Using quantum cryptography, you can tell when someone has read your message.
(It all goes along the lines of you can't observe something without changing it. If someone along the way intercepts the message and observes it, they will change the message and you can detect THAT on the other end.)
Where the wind blows, the tumbleweed goes.
Now just imagine the ramifications of allowing secure encryption! What if Osama bin Laden had one of these terminals hooked up in his cave? Instead of using letters and his international installation of terrorists to securely transmit instructions face-to-face, he could have IM'd them! We MUST stop this trend towards privacy and technological innovation if we are going to continue to lead the world in human rights and technological innovations into the future!
If a corporation is a personhood, is owning stock slavery?
What kind of applications will absolutely require this extremely strong crypto?
With the RIAA, the MPAA, MS's DRM OS and this, I can imagine: the whole collection of Britney Spears works protected by quantum crypto.
What a waste.
* shivers *
One time pad + anything = uncrackable
Uncrackable encryption is nothing new; the problem is produicng the large sequences of random data (one time pads) and distributing them securely.
As the old saying goes, "if you have a secure way to distribute the key (pad), why not use it to distribute the message..?"
Cheers,
Tim
It's official. Most of you are morons.
IMO a single photon doesn't qualify as "Light".
Calling that a LED would be like taking something that emitted single H2O molecules and calling it a tap!
Bah humbug.
The article is unfortunately a little light on details
That's the worst pun I've read in a long time.
Bravo!
You have violated Robot's Rules of Order and will be asked to leave the future immediately.
This application is described fully in 'The Code Book', by Simon Singh, although the method was only theoretical at the time the book was first published."
Uhm... I believe this is wrong. The book was issued in 1999, and it contains this sentence in chapter 8:
Moreover, one paragraph further we see:
One of us is wrong -- either I'm reading this from an edited version of "the Code Book", although nowhere does it say "second edition", or the original poster needs to re-check his facts.
If you open yourself to the foo, You and foo become one.
I have no desire to keep on kooking. :-) That I am utterly convinced of something I cannot adequately argue is driving me *hard* to learn the necessary physics to address the topic reasonably.
:-)
:-)
But I'll do a braindump, if only to see your reaction. Warning: Unbridled speculation based off a single plausible postulate follows.
It's an interesting corrolary from crypto research that you can never be entirely sure a data source is truly entropic, as opposed to the output of even an adequately designed pseudo-random number generator. (Take a look at RC4 -- something that takes that little code to implement could certainly exist as a style of equation for atomic and subatomic scale apparently entropic output.)
Knowing that one of the least understood but most significant errors in cryptography would be utterly unknown in any other field of research lends some credence to my thinking that at least some supposedly entropic processes are really pseudoentropic. It's not that I think physics people are "morons", like one person mailed me. By the contrary, they're some of the brightest people around. I just think they're underestimating the degree to which psuedoentropy, defined as a stream of "provably random" data derived from a single seed value, can mask actual entropy. GIGO, and all that.
That being said, that I'm only slightly familiar with the apparently disproved "hidden numbers" theory that believes it directly addresses this line of thought has given me a great deal of humility. My hope is that the argument against hidden numbers tends to focus on easily detectable randomizers and is overapplied to higher level processes.
Both Quantum Intrusion Detection and Quantum Entanglement, of course, make quite a bit of sense with a PRNG in place. Of course two particles can get entangled; if both can be forged with the same seed, they'll vary with exactly matched entropy. (We use this exact property when we use RC4 as an encryption system: By XORing against matched entropy, a sender can transmit to a receiver using what is indistinguishable from pure noise to anyone without the seed value.) But what would the "seed" be? Surely not position and velocity, even if it is tempting to discretize by Planck Length. I nominate direction, defined as degree of relative dimensional translation, but then I don't have much of a place to nominate anything
Whatever the seed value might be, once two particles match in any way, any subsequent measurements of both relative to eachother would tend to be uncomfortably related, even if analyzing each bitstream directly would evidence perfect entropy. And that's what we find from what little I know about the entanglement experiments. (Why yes, I'm throwing doubt on my own words to prevent other people from kooking out on my own gnawing musings.)
As for Quantum Intrusion Detection, a correction that makes perfect sense, the presumption is that it's impossible to duplicate the seed values that give rise to the sender/receiver relationships. But entanglement is all about duplication of seed values, as for that matter is photon transmission through a non-vacuum. You can't hide the fact that states are related by simply saying that entanglement implies "states may change". Spins aren't just changing; they're changing in a manner predictable to one another. If that's possible, it's difficult to out-of-hand conclude that a supposedly intrusion-proof photon couldn't itself be split, and have its entangled partner measured upon the original having its state set. You could claim the newly split pair couldn't possibly have the same seed value -- but that's more of a technological challenge than anything else. Especially if direction is a seed value, four ninety-degree bounces would equalize direction.
There's other stuff on my mind(most notably, some annoyance with the anthropomorphized concept of "observation" and "measurement" that could be abused to presume that the "observation" of dinosaur bones sent a signal sixty-five million years previous to establish the birth and death of dinosaurs in general and that specimen in particular), but I think I'll stop playing public kook for now.
Yours Truly,
Dan Kaminsky
DoxPara Research
http://www.doxpara.com
Look up "Schrodinger's Cat" at everything2 or google. Prepare to have your head explode. It sounds like the physacists have been reading too much zen.
There are a few ways I like to explain it:
Q: does a tree falling in the forest make any sound if nobody's there to hear it?
A: The tree doesn't fall in the forest, but also doesn't not-fall in the forest if nobody's there to hear it.
It's almost as if God is lazy and doesn't figure out what's going on all over the universe until someone checks to see what happened. Most of the time, there's enough watching going on that things happen normally. However, if you set up experiments to be isoled and unobservable enough, strange things happen and you can catch God being lazy.
In the world of quantum, thing can be in a state of quantum superposition. Schrodinger made up a little story to explain the idea. Suppose you are about to keep things from disturbing a cat in a sealed box. And suppose you were able to isolate the Cat from observation. And suppose that you were to place a radioactive source in the box and a time and some poison, such that if the radioactive source underwent decay within a certain ammount of time, the poison would be released, killing the cat. Forget for the moment that we can only achieve this kind of isolation on very small scales.
Now, according to quatum mechanics, the cat's state of being alive or dead is entangled with the state of decay of the radioactive source. The really wierd thing is that the way things work in the quantum world, the radioactive source has both decayed and not decayed. It's a quantum supoerposition. Due to the entanglement, this means that the cat is both dead and not dead at the same time. Only when you observe the contents of the box does the superposition collapse into a definate state. So, as soon as you open the box and look at the cat it has either been hungry for the past hour or dead for the past hour. One second earlier, it has actually been both hungry and dead. It's really goofy. Supposedly Schrodinger later wished he had picked a better story, but now we're stuck with Schrodinger's demented story of a quantum entangled cat.
This is really how things work in the world of quantum... kinda.
The way Feignman (sp?) describes this phenomenon in his book "QED" is through a variation on the classic double slit experiment. In the double slit experiment, you have a monochromatic light source (all of the photons have the same wavelength), and a barrier with two slits in it. Due to the wave properties of all particles*, including photons, the "light waves" go through the split, and come out the other side as two sets of waves that create an interference pattern. In come places the waves line up and create double-bright spots, and other places the waves are 180 degrees out of phase and absolutely no light arrives. Suppose you were to try this experiment with single photon emitter instead of the continous light source, and throw in a way to make sure the photon goes through one of the two slits and is directed toward your photodetector. Obviously the photon goes through one slit or the other, not both. Unfortunately, in this case the obvious is wrong. If you put a photodetector at a point where the photons comming from the two slits cancel eachother out, you find that the single photon somehow goes through both slits simultaneously and cancels itself out! This is strange to say the least. Suppose then you decide to investigate further by taking a detector that will detect if a single particle has passed through it, but not block the single particle. Such detectors supposedly exist. You find that half the time the photon goes through the slit you're watching and half the time it goes through the other slit, bit it always arrives at the far detector. So, ths photon never arrives if you don't check which slit it went though, but if you check which slit it went though, it always arrives. The photon acts diferently when you watch it! I think the example makes more sense if it's described with an electron, since electrons can be attracted to the detector. Feignman may have actually used an electron is his example. It's been a few years since I read QED.
The standard way to interperet this whole thing is that the particle is in a superposition of going left and going right unless you force it to be in one state or the other by measuring it.
The whole crypto aspect comes in when you devise schemes where there are two ways of measuring something. If you measure in one way, you get the right answer, if you measure in the other way, you get complete garbage. The most practical way to do this is with the polarization of a single photon. If you send a photon in a calcite crystal, it takes one path if it's polarized along the crystal grain, and another path is it's polarised perpendicular ot the crystal grain. If the photon comes in polarized 45 degrees to the crystal grain, it has a 50% chance of comming out in either spot. You put a detector at each spot and see which way the photon came out in order to detect polarity. You use this to do secure key exchange in the following way: the sender randomly picks to send each photon polarized in one of four orientations (vertically, hozontally, and two ways diagonally.) For each photon, the reciever randomly decides to orient his detector rectilinearly or diagonally. After measuring each photon, the reciever tells the sender which of the two detector orientations he used. The sender then tells the reciever which of the two detector orientations should have been used. The correct orientation reads the polarization correctly, the wrong orientation is 45 degrees to the photon's polarization and spits out complete garbage. Since you can's split a photon, you need to measure it one way or the other, not both. After the sender and reciever have talked about the detector orientations, they know which bits were received correctly and use those bits as an encryption key (probably in something like a one-time pad). Note that an attacher can bug the line and observe the photons, but in doing so his calcite crystal ends up aligning the polrization of the photon to be consistant with the measurement. An attacker needs to keep transmitting bits to the reciever, but half the time he's reading garbage bits and re-transmitting garbage bits. The sender and reciever will notice when 25% of their key bits are incorrect and know that they're being snooped on.
* I had to calculate the wavelength of a flying golfball once (thank you MIT freshman physics). The wavelength of any particle is a constant times one over the momentum of the particle. A golf ball has a hell of a lot smaller wavelength than any observed photon, due to the extremely small ammount of momentum carried by any routinely occuring photon seen on Earth.
Copyright Violation:"theft, piracy"::Anti-Trust Violation:"thermonuclear price terrorism"<-Overly dramatic language.
 
In introductory physics, this is where they tell you that light is a particle and a wave, then about Schrodingers Cat, and about Heisenberg uncertainty (the more exactly you know the position of a particle, the less exactly you know its momentum, and analogous relationships with wavelength, etc).
 
Wow!, say all the young physics students. The world is inherently unknowable! Take /that/, determinists!
 
Sadly, the young physics students do not understand. The paradoxes "explained" by the above arise from the fact that a photon is /not/ a particle. It is also /not/ a wave. It's something else. But it's really useful to describe as a particle - sometimes. Other times, it's useful to describe it as a wave. We have reams and reams of equations and theorems to deal with particles and waves, so when we can model a photon as one of them, life is easy. However, since both the wave model and the particle model are inherently wrong, if you set up an experiment properly, you can produce what seems to be a paradox. Heisenberg uncertainty merely describes the breakdown of the two models mathematically. Schrodinger's Cat is an /analogy/ only - it describes a phenomenon that only applies to things like photons and electrons.
 
Interestingly, once you measure a particle/wave, you change it - since it is impossible to measure something without interacting with it. The first explanation most people hear is that when you measure a photon as a particle, there's something about a waveform collapsing, and it "becomes" a particle. This is easy to understand, but is, unfortunately, pure rubbish. If you measure it as a particle, you will get some results that are consistent with it being a particle, and you will change something about it. That's all.
 
So to get to the encryption (although I'm sure this is already (-oo, offtopic)) here's how it works: find a particle that will change in some way measurable if snooped on. Have the sender and receiver each come up with a random sequence (polarizations). Using your photons, find the common choices in the random number streams. Now - if the photon is snooped on, (measured too early) you can tell. Even if you don't notice the snooping, unless the snooper picked the same sequence of common choices, (s)he's left with nothing. And that's the end of my post.