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."

Comments

Glowing

[Renraku]

If you had an entire array of these single-photon lights, couldn't it add an eerie glow to an object? Hopefully we can nanoscale these LED's and make things glow eerily.

Re:Glowing

[enneff]

There is absolutely no way, even if you had a MASSIVE array of them, that you could observe the light emitted by these LEDs with the naked eye. A standard LED emits many millions upon millions of photons every second, whilst these only emit a single one.

Re:Glowing

[QuMa]

Actually, under the right circumstances the human eye can detect a single photon. However, due to the preprocessing done by the brain this signal doesn't actually reach any conscious part of your brain (for lack of better terms). But you don't need that many photon's, 10 or 20 should be perfectly detectable under the right circumstances.

Re:Glowing

[Cramer]

Additionally, the density of photoreceptors in the human eye is too low to reliablly detect one stray photon. However, if the photo hits a receptor, it'll fire.

As an aside, photons aren't the only thing that will fire a human photoreceptor...

Re:Glowing

[Hittite Creosote]

You wouldn't use these LEDs to make things appear to glow, as making a multiple photon emitting LED is far easier than making one that only emits one photon at a time.

LED Uses

[sneakybilly]

So I guess these things aren't for flash lights :)

Re:LED Uses

[tamboril]

depends on how you define 'flash'

Re:But it may still be hackable

[CoolVibe]

You forgot another tacktic: replay attacks.

uncrackable encryption or no, that's just cool

[anotherone]

All that I want to know is how exactly they know that it's only emitting one photon.

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...

Re:uncrackable encryption or no, that's just cool

[os2fan]

You could {turning logic}, but it would be nearly as slow as Windows XP {MSCE bait}

Re:uncrackable encryption or no, that's just cool

[vinnythenose]

Dammit I blinked. Hey Bill reset the machine, let's try again, I'm sure I'll see it this time. Dammit, I keep blinking and missing the photon.

One Time Pads and Quantum Entanglement

[Anonymous Coward]

The article is unfortunately a little light on details. The application of these devices seems to be for sharing key material for an OTP. Seems that it could be considerably more practical than the quantum entanglement of particles methods previously discussed.

Re:One Time Pads and Quantum Entanglement

[n6mod]

The article is unfortunately a little light on details

That's the worst pun I've read in a long time.

Bravo!

Great.

[autopr0n]

. First they build the Super-kamakamode[sic] that can detect a single photon, and now they have ablity to emit them one at a time to!

And that doesn't even get into their cool anime and hot women.

But seriously, this is going to require a bit of work before it's totally practical for mass usage, right now they would have to use a huge photomultiplier tube in order to actually sense a single photon. I think it'll be a while before CCD or CMOS light detection is that good...

Or hey, maybe we'll all go back to vacuum tube computers :P

Re:Great.

[fok]

They could use it with the single-atom-transistor and the single-slectron-memory and produce a single-IC-motherboard...

Wiretapping is not a concern...

[mbessey]

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

Re:Wiretapping is not a concern...

[vinnythenose]

The only way I coudl think of off hand (and believe me, I'm no quantum mechanic) would be to do the intercepting on either end, either before the photon is sent, or after it is received. Presumably there would be circuitry somewhere that would be working with this. Unles everything transmitted in photons. (press a key, fires off a photon to keyboard, keyboard fires photons into computer, motherboard fires photons.. .etc, etc.)

Re:Wiretapping is not a concern...

[Amazing Quantum Man]

and believe me, I'm no quantum mechanic

Darn it, that's disappointing, because I had a quantum that needed some repairing. Now, if I only knew where it is and where it's going, then I'd have something.

Re:Wiretapping is not a concern...

[Birdie-PL]

Not exactly. The line can be easily tapped but then you have problems with recreating the signal.
When using two orthogonal quantum states, the eavesdropper has 50% chance of recreating any given state, even assuming that it was fully destroyed.

Funny thing is that you do not have to measure a photon (thus collapsing its quantum state) to obtain some information. One of the most clever attack ideas was to entangle trasmitted photons with your own and take measurement after both parties exchanged information via public channel. It was proved only in '98 that a scheme developed in '84 by Bennett and Brassard (BB84) is secure to such attacks.
See my slides on quantum crypto for a high-level look at BB84 and other stuff related to quantum computing and its applications to cryptography.

Uncrackable?

[coolmdriver]

Isn't that what they say about every encryption method when it comes out?

Re:Uncrackable?

[epsalon]

But quantum crypto is proven to be uncrackable. Just like one-time-pad.

Re:Uncrackable?

[madenosine]

No, they say it is very hard to crack. Quantum encryption is backed by physics, not a complex algorithm.

Re:Uncrackable?

[bugg]

What's your definition of proven?

Considering quantum cryptography is still theory, and there have been no repeatable experiments that prove that cracking it is not possible, a more accurate statement would be "quantum cryptology, by today's understanding of quantum physics, would be uncrackable."

It's very hard to prove that something is not possible. Especially something that has only existed in theory.

Re:Uncrackable?

[Hittite Creosote]

Well yes QM is a theory, but so is Gravity. That doesn't mean apples are going to rise tomorrow. Anyway, the main point is not that the code is uncrackable, but that you cannot intercept the key without being given away. Being able to crack someones code is often not that useful if they immediately know you've cracked it.

New technology

[Dirtside]

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!

Re:New technology

[Migelikor1]

Somebody has played WAAAAYY too much civilization or civ2. On that note, we should route our spare chariot units to Afghanistan, they're not much use now that we have stealth technology, but we might as well throw them onto troop transports.

Re:New technology

[DoorFrame]

Well, considering our current situation in Afganistan and the number of cities in the United States, I would switch the government of the US to Communism first (accepting the 5 or so years of anarchy since we're not a very religious people). This would allow us to better handle corruption and place us in a very strong military position. You won't need to to put the social slider to 100 if you can obtain through trade or conquest more luxury items. I hear Afghanistan is chock full of dies and gems. We'll be set.

Wanna trade world maps?

law of indeterminacy??

[ZeroConcept]

Are they referring to the Heisenberg Uncertainty Principle? What is the law of indeterminacy??

Re:law of indeterminacy??

[_ph1ux_]

I was gunna publish a law - but I couldnt determine what it should be about.

Re:law of indeterminacy??

[karlm]

What is the sound of one photon clapping? (Read below about the double slit experiment if you don't get it.) I also put a little bit about the crypto applications at the bottom of this post.

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.

Re:law of indeterminacy??

[aqu4fiend]

You've made a couple of mistakes in your post. Although it's really cool to learn about Schrodinger's cat in freshman physics, once you get into the math of it, it's not quite as it seems. When physicists started examining quantum behaviour, they started with a certain frame of reference. Two very basic concepts in this frame of reference are the particle, and the wave. Light had been "proven" to be a wave phenomenon many years earlier by refraction experiments. However, all attempts to detect the medium through which it moved were in vain (see esp. Michelson & Morley). Einstein's work on the photoelectric effect (which earned him his Nobel Prize) "proved" that light was a particle phenomenon - light was composed of photons. The sometimes-particle-sometimes-wave nature of light is referred to as particle wave duality. Duality was also observed in other seemingly self-contradictory experiments (e.g. the oft-quoted double slit experiment).
&nbsp

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).
&nbsp

Wow!, say all the young physics students. The world is inherently unknowable! Take /that/, determinists!
&nbsp

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.
&nbsp

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.
&nbsp

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.

Re:law of indeterminacy??

[karlm]

Thanks for clarifying. We mechanical engineers aren't known for our particle physics. Most of what we get is hearsay.

Obviously thermal oscialtions in atoms are going to screw up any measurements of an atom's wavelength, but I didn't realize that the effects were totally absent. At what point does the particle/wave duality approximation break down? Above a mass of 4 AMUs? Below a velocity of 0.5 C? I'm sure it's more complicated than that, and I ask way too many questions, but I'd be interested in finding out how my 8.01 profs lied to me.

Professor Rivest told us about Adi Shamir's way of "breaking" quantum crypto. I described it better in another post, but basically you send photons into the photon emitter when it's not transmitting and look at the photons comming back in order to learn about the internal state of the transmitter. It's a cheap hack, but I'm not sure I would have thought of it. And of course, there are simple countermeasurees, like photodetectors in your transmitter.

color

[Doppler00]

Hmm... I wonder what color that photon is? How can they send a single photon through a fibre optic cable and not loose it and still be able to detect it?

Re:color

[mikey13]

It shouldn't have a color. The color of light is determined on its wave length, and if there's only one photon, it wouldn't have a wave length. That's like asking what the color of an electron is: there is none because it cannot reflect light (photons).

Re:color

[AndrewRUK]

I think it may have a colour (but see below for why it may not). The wave-particle duality says that the photon has a wave associated with it, and that wave has a frequency given by dividing the energy of the photon by Plank's Constant (E=hf, or f=E/h) Whether it actually has a colour will surely depend on what that frequency is. If it is ouside the visable part of the e-m spectrum, it has no colour, in the same way that, for example, a radio wave has no colour.

1 photon? That doesn't seem like a bright idea.

[jdrogers]

Yeah, so we have the law of indeterminacy preventing encryption cracking, blah, blah blah.

But if we are going to consider laws of quantum mechanics, we only have a finite (less than 100%) chance of detecting the photon. So the LED will have to emmit multiple photon so there is a 100% chance of detection.

But then the indeterminacy law breaks down, doesn't it?

British usage

[kingdon]

Standard UK usage is to say "Avis are renting me a car", "parcelfarce are idiots", etc. Yes it is strange if you are used to the US practice of using the singular, but it isn't just for the BBC.

Irresponsible

[SumDeusExMachina]

This is certainly an astounding development in the field of photonics. Maybe now we can all get rid of programs like PGP that leave us vulnerable to government backdoors and move to some real encryption. Quantum encryption, by its very nature, is unbreakable. I thought that I would barely live to see its advent, but now with this it looks like it could be just around the corner.

However, one has to wonder what kind of restrictions that will be placed on this. What would you be able to do with unbreakable encryption? Share information on human rights abuses with your friends? How about plan the destruction of a high-profile government building?

The point is, it's time to show a little responsibility in the academic community. Just like the scientists who go ahead with playing God with stem cells before the ethical ramifications have been fully explored, these researchers have unleashed an unholy nightmare on the world that won't be fully realized until it's too late. It's bad enough that al-Qaida used GPG to communicate and coordinate their plans to commit atrocities agianst the US, but how much safer would you feel knowing that now not even the NSA can decypher their communications? Or even intercept them? It sets a dangerous precedent, and I think they ought to fully understand what they are bringing about before they actually release a prototype.

Re:Irresponsible

[Doppler00]

I was not aware that PGP had a backdoor. Who discovered this? There may be many even be loopholes with open source encryptian packages that are only known to some mathmaticians in the U.S. government. I don't think you can ever have 100% security with encryption.

Re:Irresponsible

[billstr78]

I agree that sioe scientists should think a little more about the social ramificactions of a technology before it is fully developed, but in this case, they are not doing much more harm than the cipher writers of centuries ago did when those codes were "un-breakable".

The problem is that breakable codes can work against us as much as they work for us. If a top general was sending plans about where they were going to look for members of the al-Qaida network next, I would want them to send it using a truly un-breakable. We have face the fact that people can transfer information in a fashion that does not allow any one else to find out what was transfered. There are many covert channels (stenography) that the al-Qaida network uses that are already very difficult to de-crypt.

Re:Irresponsible

[RoninM]

Well said! I've been lobbying Congress for years to ban all forms of person-to-person interpersonal communication, including encrypted forms. Most Congressmen, are blissfully unaware of the inherent danger in whispering and face-to-face communication in secluded areas, and refuse to place the proper restrictions upon its use until we can more thoroughly investigate the ethical (read: political) ramifications! I hope, anyway, that it's just naïveté. One Senator, who shall remain nameless, seemed to agree with my viewpoint, but wanted to meet in private to discuss it! If that's not proof of the anti-American corruption that plagues our government, nothing is! Needless to say, I turned down his offer, but I won't judge him for his evil actions. Everyone knows the government rules by divine right, and God works in mysterious ways.

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!

Re:Irresponsible

[tuxlove]

Maybe now we can all get rid of programs like PGP that leave us vulnerable to government backdoors and move to some real encryption.

Quantum encryption will not replace PGP or any other form of encryption, so far as I see. It's only good for point-to-point encryption of data, protecting someone from eavesdropping on the data stream between those two points. You can still spy on the data beyond either end of the point-to-point link. This technology will be useful for, say, banks who have geographically distant computers passing financial data back and forth, connected by a dedicated link which is physically secure on either end.

This won't be too useful for Joe Internet User, because he doesn't have a direct optical link to all the sites on the Internet he wants to connect to. He connects to an ISP, who connects to another upstream provider, etc., up to the network backbone. Even if each hop was connected via a quantum-encrypted link, the routers themselves are still vulnerable to "tapping", as are Joe User's computer itself and the sites he connects to.

Even if Joe User had a secure direct link between all sites he connects to, he'd be SOL if someone broke into his computer and took his personal documents or the like. So, Joe still has to encrypt personal information above and beyond the encryption provided as part of the data transport. That way, if he's hacked, they can't be discovered, and if he sends them across the net they can't be spied by taps on the various routers between him and the data's destination. Joe can't use quantum encryption for local data, because it's not usable that way. Quantum encryption is only useful as a method of transmitting a one-time pad key between two points, not for encrypting data on a permanent basis on one's hard disk. Read up on one-time pads to see why (the key is as large as the data- not too useful in most cases). So Joe still has to use conventional encryption to truly protect himself.

Re:Irresponsible

[TheAwfulTruth]

It didn't have a back door, it had a security hole (bug). Doh!

Re:Irresponsible

[_typo]

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!

The US has a death penalty. "Lead the world in human rights"??? You must be joking!

Re:Irresponsible

[_typo]

Share information on human rights abuses with your friends? How about plan the destruction of a high-profile government building?

How about running an efficient organization that controls world economy and supports major forms of terrorism. (No, not al-Qaida, the US Govt. who supports the worst terrorist state the world has known in the past 1000 years or so. That state being Israel naturally.)

Just like the scientists who go ahead with playing God with stem cells before the ethical ramifications have been fully explored, these researchers have unleashed an unholy nightmare on the world that won't be fully realized until it's too late.

Who has played God with stem cells? We're nowhere near as advanced. But now I'm curious, this "unholy nightmare" would it be the cure for cancer? Parkinson? Cause that's what the method promisses.

It's bad enough that al-Qaida used GPG to communicate and coordinate their plans to commit atrocities agianst the US, but how much safer would you feel knowing that now not even the NSA can decypher their communications?

First I wasn't aware that they used encryption at all. The attack was fairly low-tech. And as for the NSA not being able to decypher communications...reality check...they can't now. My 4096bit PGP private key isn't going to be broken anytime soon.

The point is, it's time to show a little responsibility in the academic community.

The point is others like you have mentioned these things regarding the atom bomb and other such developments. Get this once and for all, scientists by definition create science (that was stupid!) which also by definition is a tool. Invented by a few smart ones to the used by the masses. This leaves you with two options:

1-Label as irresponsible the guy who invented the first boat that eventually lead to the slaughtering of the American natives and other such atrocitys. Label as irresponsible the guy that invented the blade, the fire arm etc, for the damage that those caused has not yet been fully understood.

2-Shut Up! (This may seam like flamefesting but is a real point) If it weren't for these developments I wouldn't be awnsering you in a public forum on the Internet (what's that) inside my room, a few meters away from a bathroom. I'd be shouting an incoherent form of speech inside a cave in the middle of some forest. Now which one do you choose?

The grey reality is that scientists can't be bound by ethics. They're the brains not the conscience in our society. We do need a better conscience but we're not doing any good by trying to force scientists to refrain from making progress. The Vatican tried that already. Galileo's book where he chalenged the idea that the earth was the center of the universe was on their list of banned books up until 1992. By 1992 2 new theories had been formulated and proven wrong (Newton's and Einstein's) and a third was on it's way (superstring theory). What do you think would have happened if the Chuch had gotten it's way? What do you think will happen if the US gets their way?

Re:Irresponsible

[fishebulb]

actually they didnt use GPG, they used PGP. but more importantly they also used face to face after they realized their sat phones and encryption was being eavesdropped on

I feel just as safe as i always did. spying is not always the answer, and outside of complete 1984, its impossible to spy on everything which would be required to find out about the plots.

I personally dont see an ethical implication. Id be more worried about researchers outside the US doing something than acedamia world. WHen the US prevents research here, it will move elsewhere. but youd did have a point, the ramifications should be explored BEFORE banning said research

i think the NSA/CIA should do a better job in the first place so we dont have to play cleanup. they should be preventive, its no secret other people deeply hate the US, this will alwas exist, but when we screw around with their lives for the sake of "democracy" (or whatever rhetoric they used for overthrowing govts)

Re:Irresponsible

[RoninM]

...That state being Israel naturally.

The United States supports Israel because it is a democracy with similar values. Note, however, that the US, despite its clear loyalties, is not above official rebuke of Israel's actions, e.g., the reoccupation. I am amazed that you can distort truth so readily while turning a blind-eye to cold facts. It is a fact that Palestine houses many terrorist groups--Hamas, for instance--that have gone unmolested by the Palestinian government. Arafat has, many times, excused this fact by saying he is not in control of the terrorists and cannot exert control of the terrorists. It is a fact that only this past week Arafat made a symbolic, and mostly meaningless move, to shut down a small fraction of Hamas and only then under threat. It is highly likely that, as before, those arrested will be released. Yet you ignore this. More, you ignore the fact that the US, under the Clinton administration, endlessly negotiated with Israel and Palestine and put forward a truce, accepted by Israel, that gave Palestine 95% of its demands. Arafat refused, clearly demonstrating his unwillingness to compromise and the lie that is his pledge for peace. If Arafat cannot accept 95% of the Palestinian demands handed to him on a platter, and cannot stop the terrorist groups, then what is his purpose? If he is so stubborn and inept, he should step down. Yet he will not, and you will support him, all the while ignoring the cold, hard facts that Palestine sponsors the murder of Israeli children, supports the murder of Israeli children, and--by refusing a compromise slanted heavily in their favor--causes the murder of Palestinian children.

What do you think will happen if the US gets their way?

This comment would be offensive if it weren't so blatantly moronic and baseless. Lest you forget, it is the US that has pioneered the use of stem cells and biotechnology. The transistor? The television? The phonograph? Maybe the telephone (although there's at least a dozen claims to creation, 2 from Italy)? Stephen Hawking's voice (but not Stephen Hawking)? The Internet? The list of US technical innovations goes on and on and on. To claim that the US is a ludite nation is nearly as much a flight of fancy as your claim that Israel is the worst terrorist state to exist in history. Israel's not even the worst terrorist state to be on the Gaza strip. And to claim that the US wishes to halt the progress of technology is silly while you support Palestine and other nations with a strong fundmentalist movement that would have these countries ban television, the Internet, music, etc.

That said, I don't agree with Bush's stem cell research decision on any level. It was a political cop-out which showed neither the strength of Christian morality his supporters claim or the secular stance that I would prefer. You paradoxically excuse his decision, however, by saying that non-scientists should serve as the conscience of society. Isn't this what Bush was (expected to be) doing?

Re:But it may still be hackable

[Jon Howard]

The only way to make the output look the same as the input (for a man-in-the-middle attack) would be to break the entanglement of the source photons, read the data, and entangle the output photon with the source photons. Currently there is no known or theoretical technique to accomplish this task, but I may be missing something.

Re:But it may still be hackable

[mbessey]

Replay attacks are a protocol problem, and are best handled at that level, with timestamps, for instance.

Quantum Cryptography is all about protecting against undetected interception of your signal. If the detection problem gets solved, this could be a real revolution in the security of communication links.

-Mark

Any links to the method?

[Fjord]

I tried "law +of indeterminacy" encryption and other combinations on google, but it all came up blank. Does anyone have a link describing how to use this for encryption?

Re:Any links to the method?

[Hidyman]

The single photon led would not be used for encryption per se.
It would make the link between 2 points secure because the stream couldn't be read without the receiver knowing that the stream had been tampered with.

First, a single-photon LED...

[Tsar]

...next we'll have single-neuron Slashdot posters.

Look, the future is now!

Re:First, a single-photon LED...

[redcliffe]

We already do. They're called anonymous cowards usually. Some Anonymous Cowards are a little smarter, but most aren't.

Re:First, a single-photon LED...

[hearingaid]

Well, one neuron would be better, yes ;)

Re:First Posts

[jaavaaguru]

mmmmm I know I didn't just wanted to get in the top ten

Do the people who get first posts ever use correct grammar and punctuation? the phrase "I didn't just wanted" does not make sense. Perhaps you missed a comma?

And back to the topic on hand...

The laws of quantum mechanics dictate that it provides a way to guarantee that no-one has intercepted that key

Cool. That's half the insecurity problem solved. Or is it? In cryptography are most breaches caused by keys not being kept secure, or by algorithms being cracked?
When DES was released, didnt they say it would never be cracked? Well look what happened there. In fact, it's been done several times now.

Never say Never.

just teleport it

[abes]

I remember seeing a documentary on someone who managed to teleport a photon using entanglement. While I'm sure the equipment/setup/everything is much more expensive, it could theoretically provide an even better method of secure communication. While you might not be able to listen in without diverting the photon from its destination, it is possible to stop the photon period (also as one poster already mentioned, you can't allow for a perfect world, so its always possible for photons to be dropped [or appear to be dropped] requiring another photon to be sent out, and thus making the system again insecure).

Re:just teleport it

[mtheorist]

Teleportation by use of the quantum entanglement method is not actually teleportation, per se. The idea of teleportation here uses the fact that if the quantum numbers of two particles are exactly the same (except those of location) then the particles are indistinguishable. Quantum entanglement uses this by allowing two entangled particles to transfer properties from one place to another, meaning that this electron I have here with n=2, l=1, m=0, and s=1/2 can transmit its characteristics to another electron so the two are exactly the same. Using this on a large scale, if enough particles were entangled one could create a duplicate of something X miles away, destroy the original (convert it to energy or whatever), and thus have "teleported" an object.

Still Waiting

[Effugas]

Physics kooks annoy me. They do. The Alexander Abians, the Time Cube guys, all of em have always bugged me. They've always had the feel of someone who feels themselves too smart to actually do the research to understand something.

So the fact that I hold tremendous doubt in something the physics gurus all take for granted *really* bugs me.

But, I'm telling you. Sooner or later the guys pushing quantum entanglement(*nervous twitch* spatial PRNG *nervous twitch*) will meet up with the guys working on quantum encryption, have some kind of matter/anti-matter postulate collision, and I'll have this big goofy smile on my face.

I'm telling ya, neither work particularly well by themselves, but in the context of the other, both Quantum Crypto(states can't be copied) and Quantum Entanglement(states can be copied, at FTL no less) are completely borked. It's the only kook conviction I haven't been able to shake, and you'll have to email me personally if you want to suffer through my full kook reasoning on it(you can probably guess what it is). But I'm telling ya: Next few years, possibilities are getting shuffled.

Yours Truly,

Dan Kaminsky
DoxPara Research
http://www.doxpara.com

Re:Still Waiting

[Jerf]

Regrettably, quantum intrusion detection (as this isn't really encryption) and quantum entanglement correspond to "states can't be undetectably read (and subsequently re-created and sent onward)" and "states can change at a distance, but not meaningfully at FTL speeds".

When stated more properly, it can be seen that there are no conflicts, and one isn't going to "save" us from the other. Quantum intrusion detection depends on the uncopyability of certain states (else the intruder could recreate the photon and send it along undetectably). Quantum entanglement has other significant limitations, which ban any form of communication whatsoever at FTL speeds, and make it impracticably difficult to use it in any significant way otherwise.

Keep on kookin'. Reading the Slashdot headline takes on particle physics will definately assist in that endeavor.

Re:Still Waiting

[Kz]

In Quantum teleportation, states aren't copied, since de original measured state is destroyed by the measurement. The resulting 'copy' is not a copy, but a 'reconstruction' of the original; the same down to quantum indeterminancies.

And the FTL part isn't correct either, since the teleportation needs a 'classical component' via normal information transfer. The 'spooky action at a distance' (as Einstein called it (have you read his article on that? very interesting reading)) is FTL, but can't be measured without destroying the quantum state.

Re:Still Waiting

[Effugas]

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

Re:Still Waiting

[Effugas]

The duplication of quantum indeterminancies suggests quite strongly to me that they're not so indeterminate after all. I'm speculating that there's a psuedoentropic function on the quantum scale.

If nothing else, an algorithmic function universally deployed either in space or matter wouldn't *need* to be transmitted, thus matching the asymptotic FTL speeds that seem to be required. How long does it take to transmit nothing at all?

I'm pretty much resigned to the fact that this is going to suck up about six to eighteen months of my life someday, in which I'll actually have read and completely grokked Einstein's spooky action paper.

Until then, the only reason I give these thoughts any credence is because they're my own.

Yours Truly,

Dan Kaminsky
DoxPara Research
http://www.doxpara.com

Re:Still Waiting

[Jerf]

Your clarification was helpful. (High praise from me, esp. while wearing my Slashdot hat.)

I poked around a bit on the net and HVT is still up for debate in some physicist circles. It's not well respected, but I don't know that we could call the case closed.

I'd still stick with my gut, that even if hidden variables exist that explain this stuff, we're not going to be able to access them, but when it comes to physics, I'm not into dogma.

Your post was stimulating. (And of course the "Intrusion Detection" bit I think is general, not aimed specifically at you... yes, technically thats in the cryptography domain but most people read too much into the word "cryptography".)

Re:Still Waiting

[Effugas]

Jerf:

Your respect is much appreciated. I'm maintaining a healthy amount of doubt in my own ideas, so I do appreciate a bit of respect in them from those who know quite a bit more of the nuts and bolts than I.

I see the hidden variables(or spatial PRNG seeds, or whatever) as being useful in the sort of way chemistry operates: Useless for individual predictions, but critical for larger scale operations and cleaning up some unparsimonious nastiness(like asymptotic data transmission rates; see my other reply to this thread).

Quantum Intrusion Detection actually bugs me more than entanglement. I actually believe two particles can be made related over some distance(my quibble is that their entropy itself was made related, thus obviating the need for a message to be sent between them). Proving a negative -- that it's conceptually impossible to duplicate some data stream -- is alot tougher, and I sense dangerous levels of overconfidence on the matter.

Physics is not a field that's particularly compatible with realities of security research. Schneier's analogy of planting a ten foot steel pole in the ground and expecting the enemy to drive right into it isn't something that lends itself well to a realm where entire classes of theory aren't developed because the math is too obscure to work with. "As long as you're concerned about the notes, you can't create music." And as long as you're struggling to get there in the first place, it's impossible to really understand what might go wrong. Airliners were a mature technology long before they were an obsessively safe one.

I really think we don't know enough about the nature of quantum reality to be making absolute statements of uncrackability. But then, it's easy for me to claim ignorance; I just know the security side, not the physics.

That's going to change, someday. Hopefully I won't go kooky because of it. (Now *there's* a statement that could seem tremendously ironic in a few years!)

Cryptography can be a much wider field of inquiry if you let it be. It's actually equal parts psychology and mathematics, for instance.

Yours Truly,

Dan Kaminsky
DoxPara Research
http://www.doxpara.com

Re:Still Waiting

[Iainuki]

In 1964, Bell proved what is commonly known as the "no-hidden-variables" theorem. This result is more properly understood as a proof that certain aspects of quantum mechanics are incompitable with a LOCAL hidden variables theory. This theorem is quite well-known, at least among physicists with any philosophical tendencies or historical interests, and also quite solid. A fully mathematical and rigorous proof requires graduate-level quantum mechanics, though you can make an effort which captures the essence using only ideas from an upper-division undergraduate course. However, the result is not trivial and so will require both math and quantum mechanics background, and some patience to work through.

While the proof is more difficult, the result is simply stated and relatively simply understood. Bell showed, using conservation laws and the specific indeterminacy required by quantum mechanics, that a measurement of one particle in a pair of linked particles could provide the experimenter with information about the other particle regardless of the size of the spatial separation of the particles (Bell's actual proof was both more and less specific than this, but that is the essential idea). The way this information was expressed was in the form of an inequality which could not be obeyed by local hidden variables theories. In the early 1980's, Alain Aspect et al. did an experiment on a modified version of the situation Bell examined, and found that the inequality was, in fact, violated. The original experiment had statistics which were extremely skewed in favor of the quantum mechanics interpretation (some ridiculous number of standard deviations; eight comes to mind, but I'm not sure). Since then, better experiments have been done which have increased the certainty even further. Thus, Bell's theorem is very solidly established.

What does this mean? It means that local hidden variables theories are not capable of accounting for quantum effects, and so do not describe our universe. "Local" here is a technical term meaning, "no signals travel faster than the speed of light." The motivation for this is that faster than light effects, when viewed from certain reference frames: they may travel backwards in time, generating causality paradoxes and all sorts of other nonsense. "Hidden variables" means that to each quantum particle a specific, determined state is assigned at all times. So a "local hidden variables theory" posits that each particle has a specific state and that these states may not influence each other with faster than light effects. These theories are what Bell proved are not able to explain quantum mechanical effects (btw, it has since been proven that Bell-like effects cannot be used to transmit information faster than light).

It looks like this post is positing a local hidden variables theory: the quantum particles carry "seeds" which do not influence each other faster than light. This is the kind of theory which Bell and Aspect disproved, so if this is the correct interpretation, it's almost certainly wrong (to whatever number of standard deviations the latest version of Aspect's experiment has shown).

I won't speak on the notion of randomness vs. pseudorandomness, since I am not well enough versed in information theory to make rigorous distinctions.

Direction as an independent quanity doesn't make much sense; position and momentum are vector quantities, so they already include notions of "direction" as normally defined.

Here I will diverge from the generally accepted to express my own opinions. The measurement problem is an unresolved problem in quantum mechanics which is too philosophical for the tastes of many working physicists. I personally think the answer lies in careful consideration of the arrow of time and decoherence, but that's mostly just speculation on my part.

Re:Still Waiting

[Effugas]

First of all, let me say that I really appreciate the rigor of your response. The better responses I receive, the more I'm motivated to bring my own level of knowledge up to that of my peers. So, to be blunt, thanks for helping me think :-)

I have a few thoughts on the matter, now that I understand the presumptions behind Bell's Inequality(mainly, that the entire set of hidden variable theories would have to output non-QM results), but I'm going to sit down with my ex-roommate(degree in Physics from Purdue; couple years in optics at Intel) and work things out correctly first. Anything less would be SNAKO(Situation Normal, All Kooked Out) :-)

Too many parentheticals :-)

--Dan

Not Useful for Packet Networks

[pryan]

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.

Re:Not Useful for Packet Networks

[switchninja]

You have the routers and switches along the path to the destination perform the encryption. Much in the same way current IPSec VPNs are created. This way the encryption remains transparent to the application as well.

Re:Not Useful for Packet Networks

[IAmHansemann]

For practical quantum crypto systems, which you can build now, you are right. OTOH, there exist (theoretical) scemes which allow for secure transmission of quantum information over long distances, using quantum repeaters.

Going to long distance means (in this context), that the required resources increase only polynomially with the distance (opposed to an exponential increase if you do not use a quantum repeater).

Theoretical means, that there is no experimental implementation of a quantum repeater yet. Nevertheless, it would be much easier to build it than, say, a fault tolerant quantum computer.

Using these techniques, it is possible to build secure switchable user-to-user channels, which are secure even if all repeater stations or switches are under the control of an allmighty eavesdropper (Eve). As always, Eve can prevent you from communicating, but if you can communicate, you can be sure to communicate privatly.

For more details, see e. g. quant-ph/0111066.

IAmHansemann

Abstract

[Aetrix]

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.

NOT Uncrackable

[MikeyNg]

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.)

Re:NOT Uncrackable

[CaptainSuperBoy]

I have between little and no understanding of quantum anything, so forgive me if I'm off base. Would the encryption method you're describing require the use of quantum computers, or would it be possible on normal binary computers? It would seem to me that in order for this to work, your computer would have to support a bit whose value was undetermined (a qu-bit).

Re:NOT Uncrackable

[jfedor]

You are mistaken. It is uncrackable. Perhaps not very practical. Read the book.

-jfedor

Re:NOT Uncrackable

[MWright]

It is uncrackable.

It does detect if someone is eavesdropping, but it detects it as the key is generated, not when you send the message. Your post implies that you send the message, and can detect if anyone eavesdrops... this is not the case. Two parties use these quantum effects to generate random numbers... they can detect if someone is eavesdropping on this; if someone is, they don't have to use that key (even if someone does try to eavesdrop, it won't work, by the way). Once they have this key, they can use it in One-Time-Pad encryption, which is also uncrackable (see a text on information theory for an explanation about why OTPs are uncrackable).

Re:NOT Uncrackable

[MWright]

Quantum computing and quantum encryption are two different things. Quantum encryption technically would not even need a computer at all... as long as you have some way of transmitting and receiving photons, and some way to detect them, etc., pen and paper would be enough (though very impractical!)

Re:NOT Uncrackable

[jjeffries]

It's totally crackable, you just have to figure out how to get that half-dead cat in a box spliced into the line correctly first...

Re:NOT Uncrackable

[Caacrinolaas]

No, it would make message sent in such a manner uncrackable.

Sure, a single _bit_ could be intercepted, but as soon as that is done, the sender can simply stop transmitting.

The end result leaves the interceptor with nearly zero information. Not very usefull.

Re:NOT Uncrackable

[MikeyNg]

OK, that makes sense. Take my karma down a couple of notches for being incorrect. At least I *sound* like I know what I'm talking about. :)

I was just incorrect on the implementation of how you'd use something like this. I can see how using this to generate and "send" OTPs makes it uncrackable. My bad.

Re:NOT Uncrackable

[Silver222]

The cat isn't half dead. It's either dead and alive at the same time, or it's dead in one universe and alive in the other.

If I had mod points, I'd have modded you up as funny though...

Re:NOT Uncrackable

[IAmHansemann]

If quantum cryptography was used for direct communication, you would be right. But, quantum cryptography should better be (and often is) called quantum key distribution. This means, using quantum crypto, you do not distirbute messages, but keys only, which (a) do not contain any usable information, and (b) after having verified that noone has listened in, are used for classical one time pad cryptography.

Hans.

Re:NOT Uncrackable

[MrFredBloggs]

No, you just dont know if its dead or not. Theres nothing weird about it. Those sort of effects dont work on objects as big as a cat. Whats to stop you x-raying the box?

Re:NOT Uncrackable

[John Sullivan]

Whats to stop you x-raying the box?

Because if the cat then turns out to be dead, it's YOUR fault for collapsing the wavefunction.

Re:But it may still be hackable

[waitdyahoo.com]

Well that is what I don't understand as I read the article, it says that intercepting the proten would cause the properties of it to change..

But they also say they have no way of reading the value. Is that because they are modifying the value of the proton when they try to read it?

Vaperware anyone?

this will crack quantum crypto

[OeLeWaPpErKe]

If this thing gets somewhat more advanced you will eventually become able to use the classic "man in the middle" attack. And since there are no keys involved in the crypto, it will work if you have only a connection to the cable. Sure it will cause some extra errors, as you cannot exactly copy the state of the photons, but that will only lead to the session being restarted, wich will make the mitm attack even simpler.

I see only 1 advantage of using this over traditional electrical wires, you have to actually break the cable to get to the data, but that is also the case now with fibre-optics, so it really doesn't matter.

just my thoughts, are they good ones ? ;-)

Superconducting Fibreoptics

[Hidyman]

It seems as though for this to work we would need fibreoptics that act as "Superconductors" to keep photons from being "Lost" on the way to their destination.

There's no uncrackable crypto

[andkaha]

If a human constructed it, a human can deconstruct it. That goes for everything, always.

Re:There's no uncrackable crypto

[smack_attack]

I can use my quantum computer with quantum decryption to crack it. duh.

Re:There's no uncrackable crypto

[CyberDong]

If a human constructed it, a human can deconstruct it. That goes for everything, always.

Does that apply to the philosophy that "If a human constructed it, a human can deconstruct it"? If so, it's a fallacy...

Re:There's no uncrackable crypto

[cjpez]

While I have no real knowledge to back this up, I'm going to wager that you're wrong about this. I know enough about the quantuum world in very (I repeat: very) layman's terms to know that it's a really freaking messed up world down there.

The article seems to be indicating that they're relying on the fact that once you start observing systems you inherently change them (Heisenberg (sp?) basically), which gets extraordinarily important on the quantuum level (though not as much on the Newtonian level we're typically mired in). Read about it. I can totally believe they can create an uncrackable crypto system using quantuum principles . . .

Re:There's no uncrackable crypto

[cjpez]

Wow. I misspelled "quantum" no less than three times in that post. Brilliant.

Yeah, listen to what I say! I'm so good I can't even spell the subject matter correctly!

Gah.

Re:But it may still be hackable

[Anonymous Coward]

1. The line can still be hacked, because it is possible to put a TEE into the circuit, just as long as STDOUT looks like STDIN.

Actually, if the predictions of quantum mechanics are correct, this is not possible.

The way that this works is not intuitive at all, so don't worry if you don't understand it. Einstein, Podalsky, and Rosen published a famous paper showing that quantum mechanics necessarily leads to these kind of effects.

Their goal was actually to show that quantum mechanics was unacceptable as a physical theory because they did not believe nature could possibly behave this way. But as far as we can tell, nature really does work in these mysterious ways.

Photon Light 3!

[artlu]

Hey! Now instead of using my photon light from thinkgeek.com to light my path i can shine it on computer systems and log in or use the different colors on an ATM machine in order to get someone else's money! Not to shabby for only $30!
My $0.02.
AJ

A New Level of Precision

[Jucius Maximus]

I guess David Allen (inventor of the photon light ) is kicking himself now because he's been one-upped when it comes to lighting technology!

Re:A New Level of Precision

[Hittite Creosote]

An LED on a keyfob - a very simple idea, and very easy to make once you have the idea of marketing them.

Now, in my opinion, the really smart guy is Shuji Nakamura, without whom you wouldn't have white LEDs yet.

More accurately

[parc]

More accurately, Quantum encryption IS OTP. The quantum part comes in when you generated the pad.

Maybe not the *key*, necessarily...

[Cool Hand Luke]

"We need the detection technology for single photons," said Dr Shields. "But most of the other elements are there. It uses standard telecoms cables.

This sounds like a promising breakthough, although I can't help but wonder how far off in the future the detection technology is. I can claim that I have the key to teleporter technology, object decelerator technology (big, fluffy pillows), but I still need object accelerator technology (a large enough catapult).

Then again *yawn* this object decelerator technology is so comfy... maybe I'll just take a nap...

Re:But it may still be hackable

[CoolVibe]

Timestamps have one fundamental problem: they are predictable. It might stop a replay attack, but not cryptoanalysis.

But just a thought, if attempts are made to make the signal "undetectable", isn't that falling into the 'security through obscurity' trap?

I find the assumption of "unbreakable crypto" a bit overzealous. Every crypto scheme can be cracked, only the time you have to invest in it seems to keep growing, and things seem to get more and more complex. The reason people feel save with high grade conventional crypto (thru PKI or be it symmetrical) is that it takes a *very* long time (as in hopefully centuries) to recover the message.

AFAIK, there is only one scheme that comes close to perfect, and that's the one time pad using a (dare I say) random "key" (say, a CD-R recorded with just white noise picked up from radio traffic or stellar background noise). If the "key" is handled in a secure manner, it's virtually unbeatable. Of course there is one VERY weak factor here, and that's the human factor, but still... Oh ironic is that the one time pad system is also the most simple one :-)

Man in the middle

[mickonline]

Surely this doesn't make it properly uncrackable.

It prevents people from reading the message then passing it on, but not from reading then generating an identical one. Admittedly this is a problem with all mediums, but quantum mechanics aren't the final solution yet.

mick

Re:Man in the middle

[zuvembi]

Actually that is incorrect.

You'll have to look for a description of it, but it is in fact in impossible to eavesdrop and then resend the information. There is a very good description in "The Code Book" by Simon Singh. I'm not sure where else you would look.

Re:Man in the middle

[Silver222]

The thing is, with an appropriate key length, you can't generate an identical message. Even better, you can tell if there is someone in the middle listening in.

You really should read the book, it's extremely interesting.

no!

[autopr0n]

Mod the other post I did as redundant. Seesh.

Uncrackable encryption HOWTO

[Luke]

quantum cryptography + one time cipher = uncrackable

one time cipher + shared secrets = uncrackable

AFAIK, these are the only two that are uncrackable. the latter is impractical because of the necessity of a large quantity of pre-shared random ciphers, and the former due to implementation (but not for long it seems).

Re:Uncrackable encryption HOWTO

[Tim C]

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

Re:Uncrackable encryption HOWTO

[MikeBabcock]

The old saying is stupid ;-)

The method to distribute the key may be highly bound to specific points in space-time; that is, one may be able to get a large number of long code books to one's agents by giving them to those agents before they leave for foreign countries but it becomes very difficult to get them coded messages the same way (in person) unless they come back for them. Delivering new such codebooks in person may be possible for future agents as well.

Strongest crypto for Britney

[Yodalf]

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 *

Re:Strongest crypto for Britney

[CyberDong]

What a waste.

That's "waist". And don't forget the other parts...

no

[Anonymous Coward]

No one ever said DES is uncrackable. No one (intelligente) has said, nor will ever say, that the new AES is uncrackable. No one (intelligent) has said, nor will ever say, that public-key cryptography is uncrackable. They will say the computations to crack them are "intractable", but not impossible.

The one-time pad (Vernam cipher), however, is uncrackable. It has been used very heavily since it was first introduced (1917) and, beyond being arguably the simplest automated cipher ever devised, is still being proven to be completely 100% uncrackable. Unfortunately, since the key lengths are at least as long as the message, and the keys can only be used once, exchanging keys can be a bit burdensome. Quantum cryptography is basically concerned with ways of exchanging pads securely. If our current understanding of the Heisenburg principle is correct, then current quantum cryptography (in combination with OTP's) is 100% uncrackable.

The failures of previous ciphers, especially public-key ones, is due to underestimating the difficulty (or "intractability") of certain computational tasks, but no one would have ever claimed that they were COMPLETELY secure, just secure ENOUGH. The Vernam cipher does not rely on computation (beyond addition mod 2), and is completely uncrackable.

RTFGoogle

[mypalmike]

It's not about timestamps. It's not "security through obscurity". It's about fundamental laws of quantum physics. Try looking at these links.

it's all about the probability

[Anonymous Coward]

When M intercepts the photon burst, he naturally modifies it (Heisenburg) before it reaches B. During the verification stage (which takes place over an unsecured line), A & B have a 0.25 probability per bit of detecting that M was eavesdropping. Thus, for an n-bit message, the probability of detecting M's presence is 1 - (3/4)^n.

If we replace M with E, things become even more dire. Like B, E will choose the wrong detector half the time, but it will choose the "wrong" half ("wrong" according to the verification stage). For a message of length n, there is thus a 1 - (1/2)^n probability that E will not be able to recover the message.

Note that quantum cryptography is not meant to be used to send normal plaintext messages. It is meant to be used to transmit one-time-pads. Generally you'd want these one-time-pads millions of bits in length.

Let's suppose you create a protocol to set up an uncrackable, 100% secure channel between yourself (A) and your friend (B). I (M) am a real bastard and want to annoy you by intercepting your key and having lots of fun. You send your friend a one-time pad with your LED, let's say 1kB (8 kbit) in length. Note that this key is thousands of times smaller than your average key would be, but my calcalutor chokes if I don't use an obscenely small number :).

There is a 3e-1000 chance of me sitting in the middle without being detected (of course this probability is exponential, so a sanely-sized keywould give me very little hope indeed!). So, you send your friend 1kB and darn! someone was eavesdropping. You'd think your application would alert you at this time ("hey! I can say with literally 100% certainty that someone is eavesdropping!"), but lets say your application is terribly stupid. So, you restart and send another key. Same thing! Another few keys, then a few thousand more, then a few googol keys here and there. Damn! You've been trying to get this channel started for literally billions and billions of eons, and still you can't quite connect because someone's eavesdropping! Determined, you keep on plugging away. Millions of universes have expanded and collapsed by this time, but you still it says someone is eavesdropping!

Of course the prudent thing to do would be to write your application so that it gives up once there has been found an eavesdropper with *100%* certainty. :)

Anyway, once you finally get a key sent without a man-in-the-middle, you use that key as a OTP for more conventional uncrackable (no probability involved here!) cipher. Presumably with each message, you'd attach and encipher a new OTP along with it (or just use your LED to exchange a new OTP).

Any chemists out there now about this?

[Amyloid]

What is the source of this LED? Quantum Dots? Single Molecule? Doped Buckies? SAMs? Anyone know how they do it?

clearing up some confusion

[Anonymous Coward]

There seems to be some confusion about how a cipher can be "uncrackable". Let me explain to you the One-Time Pad, an uncrackable cipher.

Me and my friend have previous shared a secret key, which is a random string of bits, of length 10. Now I wish to send my friend a message, a bitstring which is also of length 10. I take each bit from the key, and add it to the corresponding bit of the plaintext, modulo 2 (think XOR), to generate my ciphertext. e.g. if our key is 1010010101111010 and my plaintext is 1011110110101010, then my ciphertext is 0001100011010000. The key is then destroyed (for high security, it's stored on magnetic tape, then physically burned once used), never to be used again.

Now, let's say you have intercepted a message from me to my friend. The message is 1100101010000100. The only things you know about the secret key used before are: (1) it has never been used before; (2) it as a random (and uniformly distributed) smattering of 1's and 0's. Now tell me: what was the original message?

Unless public-key cryptography, it is not prone to "key attacks" (since you have no public key to work with). Unlike other symmetric-key (aka secret-key) cryptosystems, you have no frequency analysis or algorithmic analysis to work with. So long as you don't know any of the bits of the key, it is literally uncrackable, and has been for the past 80 years.

So, then the question is, how do you and your friend decide on a key? It's not easy. The best way, so far, is to physically go to your friend's house, make sure no one else is around, generate a random bistring, copy it onto two tapes (your friend keeps one; you take the other home), and keep it safe until it's time to use it.

What quantum cryptography does is lets you send a key to your friend over a long distance. But, do to quantum mechanics, you and your friend will be alerted if someone has intercepted it.

Nothing's really changed substantially here. It's the same uncrackable cipher that's been uncrackable for the past 80 years. The only difference is that now you can generate keys with your friend over a long distance, without having to drive to his house.

Re:clearing up some confusion

[asterisk_man]

It is agreed that generating random numbers HAS been the weak point of OTP. But, this being the quantum world it is god rolling the dice. So, seemingly the only way to crack this random 'algorithm' is to get past the uncertainty principal. I dont think you are going to find many knowledgable people in the field who will say thats possible. Maybe you say, "why should we think they know what they're talking about? physical 'law' has been proven wrong many a time." To that I say...nothing since i cant predict the future. But lets just say that it doesnt seem like the randomness of the quantum world is going away any time soon. so unless you are encrypting something that must stay secret for 200 years or more i would say generating OTP via quantum effects will be good enough for now.

Entanglement and spooky action was: Re:RTFGoogle

[CoolVibe]

Heh, I did some extra reading and it's indeed promising, albeit difficult to implement. The act of observation disturbs the exchange, hence, whatever you intercept, its never the right "key".

Nifty... But it's still somewhat volatile and a lot can disturb it. I still doubt this can reliably be done in a "real world" environment

Call me sceptic :)

Badly written Troll

[horza]

Sorry, this only gets 3/10 as a troll. I appreciate the attempt at humour but you contradict yourself all over the place, and are a bit *obvious* with some attempted analogies and factual inaccuracies. Plz make the satire a bit more subtle next time.

Look forwards to next attempt,

Phillip.

Re:although, to be fair

[SideshowBob]

Umm, what??

There were no riots in ancient Rome?

Not to mention all the other things you attribute to the 19th century, which ancient Rome had (or had facsimiles of). And its not like Rome was singularly unique in any of those respects.

You might want to take a western civ. course, genius.

More accurately

[parc]

More accurately, Quantum encryption is OTP. The quantum part comes in when you generated the pad.

PED, not LED

[SpinyNorman]

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.

Re:PED, not LED

[Alsee]

IMO a single photon doesn't qualify as "Light".

What moron modded this up as insightful?!?!

His "insight" is that he can't see it, so it's not light. HELLO! McFLY!

-

Re:PED, not LED

[MikeBabcock]

PED is definately more accurate than LED ... SPED for single photon emitting diode seems just as accurate though.

How?

[2nd Post!]

Well, it's not *that* difficult.

You input energy X, enough to account for a single photon and circuit inefficiencies.

Where X isn't enough energy for more than one photon.

The problem with the detector is that it's possible to build detectors that register single photons, it just requires that someone builds one, and that shouldn't be impossible either. It's a function of creating an optic trap akin to a waveguide and lens such that the single photon has to fall into a set of paths which is appropriately matched with a CCD able to register single photons.

Re:How?

[tzanger]

The problem with the detector is that it's possible to build detectors that register single photons, it just requires that someone builds one, and that shouldn't be impossible either.

Umm... I was under the impression that photomultiplier tubes were regularly built this sensitive.

Re:How?

[2nd Post!]

There you go then :)

I don't do this for a living, I took an Optics course in college.

Aren't photomultiplier tubes akin to... opamps?

And... can you chain one to a fiberoptic cable?

Re:How?

[tzanger]

Aren't photomultiplier tubes akin to... opamps?

Kind of... but for photons. A google search for "photomultiplier tube" or "pmt" spits back tons of physics experiments but I was hoping for something like a howstuffworks description to link to in here.

And... can you chain one to a fiberoptic cable?

That's just a physical connection; I don't see why not.

Re:How?

[2nd Post!]

It's a matter of efficiency, maybe?

Cause if there's any mechanical-physical inefficiency, 1 lost photon means the transmission needs to be resent, or whatever the protocol allows for, because one lost photon could easily be one stolen photon.

It's certainly *possible*, it's just a question of is it currently feasible?

Re:Entanglement and spooky action was: Re:RTFGoogl

[mmol_6453]

Actually, I'd rather call you a skeptic. What you said doesn't stink.

Re:although, to be fair

[nido]

to finish the train of thought: "Riots have existed as long as mankind [has been oppressed]." People don't just go out rioting for the hell of it, there is inevitably some form of trigger. I won't say anything about what I think that trigger often is...

Re:Entanglement and spooky action was: Re:RTFGoogl

[CoolVibe]

So I'm not a native english speaker... :-)

(oh, and it's quite late here now... bugger...)

It really was done before

[pc486]

"The Code Book", at least the british version, does describe that this unbreakable quantum encryption actually had several sucessful attempts befor this special LED appeared. I believe it was sucessfully done though the air at up to one mile. I would quote but since I'm moving the book is packed up. If you don't own the book, go buy it. It's a very good read.

Not only theoretical.

[Mr_Icon]

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:

In 1995, researchers at the University of Geneva succeeded in implementing quantum cryptography in an optic fiber that stretched 23 km from Geneva to the town of Nyon.

Moreover, one paragraph further we see:

More recently, a group of scientists at Los Alamos National Laboratory in New Mexico has once again begun to experiment with quantum cryptography in the air. Their ultimate aim is to create a quantum cryptographic system that can operate via satellites. If this could be achieved, it would enable absolutely secure global communication. So far the Los Alamos group has succeeded in transmitting a quantum key through air over a distance of 1 km.

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.

Re:Not only theoretical.

[hephro]

The experiments you cite were proofs of concept. In particular, they could not guarantee that their light source would only emit one photon at a time and hence they had very bad security (if the light source emits two photons, you can capture one and let the other go; the two photons are correlated and you can essentially use the stolen photon to break the protocol.)

-Hein

Re:But it may still be hackable

[Cramer]

As I understand it, you cannot entangle a photon. At any rate, you cannot entangle one of anything -- it's entangled with what? Now a quantum entangled photon emitter... that's a toy! Your "key" becomes one certified photon from said emitter. (Give it a few decades and there would be a quantum photomultiplier rendering the whole mess about as useful as DES.)

Quantum physics dreams up a lot of stuff that exists only on paper. And even after we figure out how to get it off the paper, we cannot figure out how to get any functional utility from it.

Re:Irresponsible (Getting OT, sorry)

[bonoboy]

I'm sorry, I must say that for once scientists have charged ahead and decided that stem cell research is for the benefit of all humanity, and should be applauded! After the fucked up things scientists have given us (the nuke, et al) it's good that something which acts at the fundamental, medical level - not just a new toy - is being taken seriously enough that those with the knowledge are willing to risk going to jail to bring it to us.

"Ethical" ramifications are never hashed out. People just argue ad infinitum. How long, exactly, would you say they should wait? Until either everyone on earth shares the same religion or there is no religion anywhere? Until everyone is in exactly the same sociopolitical caste and there's no racism, so everyone agrees? Dream on. Stem cell research will do more to improve the lives of humans than anything prior. Just give it time to become available to everyone. Not developing it won't make anyone's life better. So why wait?

Umm.. not impossible

[cybercrap]

You can spoof bob to alice and alice to bob and just intercept the signal and then resend it. FYI, alice= sender, bob= receiver. This encryption stops you from listening in, but you could just receive the signal, ie block it from bob and make alice think you are bob and then regenerate the signal and send it to bob and he would think you were alice. Or atleast so I would think.

Re:Umm.. not impossible

[CatherineCornelius]

This introduction explains how the quantum channel is used by Alice and Bob to negotiate a key. Sure, you could eavesdrop, but having read the stream does not enable you to clone it in a way that would spoof Bob.

EU Issues Moratorium on Sense of Humor

[RoninM]

Two things.

One, I was--of course--joking.

Two, yes, I agree, it's far more humane to burden the rest of society with the cost of maintaining those unreformable few whose actions are so blatant, terrible abuses that one has to question their humanity, at all. I, like you, would rather an innocent mother and her child--displaced and homeless--go hungry, than a miserable mass murderer be given his fair end.

Now, if you want to approach the topic from the standpoint of whether the justice system works well enough to support the inclusion of such severe penalties, we'll have more to discuss.

Re:although, to be fair

[Naikrovek]

oh yes they do. people riot for any fucking reason they please. they don't need to be oppressed, the just need to know the outcome of their teams game - win or lose, they riot.

ask someone in chicago.

How abut the other end ?

[AftanGustur]

In order to use this tech you will have to create a transistor that can *detect* a single photon.

Re:NOT Uncrackable - false

[Birdie-PL]

Quantum cryptography, even in it simplest form (scheme BB73, from Bennett and Brassard) is unbreakable, even using unlimited computational power, both classical and quantum.

In short, you can create a key for one time pad (which BTW is proven to be the only unbreakable classical crypto scheme) in such a way that no-one knows it.
As for eavesdropping - you can detect if someone is eavesdropping / attacking your scheme during key exchange, so you simply can restart it. Restarting mean that the attacker can DOS your key exchange - i.e. produce noise so you won't be able to agree on the key. Thus you will not be able to encrypt any data. But you will not leak any, either.

What's more - there exist some solutions for the DOS problem - one can enhance the exchanged knowledge is a way that minimizes the chance of attacker to possess it too. But these are probabilistical schemes, not fully safe. And rather impractical as they require much redundancy and communication.

If you have mathematical background, see http://www.cs.mcgill.ca/~crepeau/CRYPTO/Biblio-QC. html for further references.

missed the point?

[kresmoi]

I have read "The Code Book" but don't have my copy with me, so please correct me if I am wrong. The impression I got from the section on Quantum Cryptography was that single photons would be used to securely transmit a full length random encryption key, where an eavesdropper could be detected and/or avoided. This key could then be used in a type of encryption known as a Vigenere Square, which (according to The Code Book) has been mathematically proven to be unbreakable when used with a full length random key. In this way, the LED in the article could be one component of a truly uncrackable encryption system. You still need a viable means of long range transmission and detection to make it practical though...

Re:NOT Uncrackable - false

[hephro]

Quantum cryptography, even in it simplest form (scheme BB73, from Bennett and Brassard) is unbreakable, even using unlimited computational power, both classical and quantum.

Do you mean BB84? I haven't seen security proofs for other protocols yet.

see http://www.cs.mcgill.ca/~crepeau/CRYPTO/Biblio-QC. html

But beware of any claims about quantum bit commitment :-)

-Hein

Random number generation

[nairolF]

This SPED (single photon emmiting diode - we may expect this name to become nearly as commonplace as LED one day) also provides a cool way to implement a true random number generator.

The basic idea is that, as far as we know, the only TRUE source of randomness in nature is the collapse of a quantum wavefunction. Basically, the state of a quantum system is really the superpostion of several "pure" states. When the system is measured (I won't go into what constitutes a "measurement", that's a never-ending debate), this superposition collapses into one of these pure states. Which state this will be is, as far as we can tell, entirely random. Only the probability of each outcome is known in advance. Besides this, all other physical processes seem to be deterministic. So any true randomness in nature must have its origin in the collapse of some wavefunction.

How do we exploit this? Fire a single photon at a beamsplitter, then measure whether the photon has been transmitted or reflected. The outcome will be random in a true sense, the probability of each outcome will depend on the beamsplitter. But, importantly, there will be no correlation between successive outcomes if the transmission : reflection ratio of the beamsplitter is 1:1. If our two detectors (one for transmission, one for refection) aren't perfect and lose a photon, we can always fire another photon, so this should even work with imperfect detectors, like a CCD.

This can now be implemented, all we need is a SPED, a beamsplitter and two CCDs. These can all be made pretty small, so might even fit on a chip, and hey presto! You got yourself a little hardware random bit generator. The only problem left is that the thing must be cooled to some pretty low temperaure.

I've always been of the opinion that a random number generator should be hardware, not software.

Key, not the message

[ph117]

I could be completely mistaken, but you're suggesting the message is exchanged using this method, rather than the key. I thought the method was used in order to allow two parties to exchange a series of bits that could be used as a one time pad. This one time pad can then be used to encrypt the message, which can be sent by carrier pigeon if so desired.

If a third party is eavesdropping, their interference could be detected and the process restarted (to generate a new one time pad that the sender and receiver know hasn't been intercepted).

Of course, one time pads are only uncrackable provided that they are generated using a truly random source, and are never reused.

Detecting a single photon using FET

[CatherineCornelius]

So far they've figured out how to emit one photon, but they don't know how to read it.

Andrew Shields and others released a paper last year on possible use of normal FET technology in conjunction with a layer of "nanometer-sized quantum dots" for the detection of a single photon. I'm not sure that the method he demonstrates there could be adapted to commercial scale crypto, but it certainly seems to be a possibility.

I'm no expert, and Shields' comments on problems of attenuation in fiber transmitters may render the unique selling point of quantum crypto (that snooping can be detected) moot, but it still looks very promising for such a young idea.

Quantum crypto already cracked

[karlm]

So, look for my previous post under this story if you're not sure how quantum key exchange works. I have a brief summer at the bottom of this post to check if you and I are thinking about the same implementation of quantum key exchange. Adi Shamir (I think) came up with a way to break quantum crypto key exchange based on polarised single photons.

Okay, so it's only an attack against uncareful implementations. The easiest way of explaining it is the case of tapping a fiber optic line. You splice th fiber optic line and let all of Alice and Bob's photons pass through your detector. You inject your own polarized photons back towards the transmitter when the transmitter isn't transmitting. (You need to predict the timing of the transmitted photons, but that should be relatively easy.) You look at the polarisation of the photons you sent out after they reflect of the internals of the transmitter. This should leak information about the polarisation of the photon just sent or the photon about to be sent, or if the system is transitioning to send a photon in a different polarisation. Most designers wouldn't think to put a single photon detector in the transmitter, becuase they don't expect photons to be comming back at the transmitter, or assume such things would be inoocuous. Of course, there's always a man-in the middle attack if you don't ahve a good signature algorithm.

A brief summary is that you have a detector that can be set up to correctly detect rectilinearly polarized light or correctly detect diagonally polarized light. One person sends single photons randomly polarized in one of the 4 directions the other person is looking for. Afterward, they figure out which photons were correctly measured and those mesurements are the key bits. Like I said, I explained it better somewhere else in this article.

Re:1 photon? That doesn't seem like a bright idea.

[fatphil]

Not necessarily if there's external synchronisation, so that the recipient knows when a photon has been dropped. A dropped photon will then be as useless to a MITM as an intercepted (thus changed) photon. However, I'm curious why you want only one photon - how to you play with quantum entanglement if you've only got one photon?
The article was light on facts to say the least. Unless there's some form of Quantum Encryption which doesn't rely on quantum entanglement that I don't know of???

FP.

Excellent satire...

[Astfgl]

...I almost spilled beer in my cornflakes! :-))

Not Encryption

[gweihir]

This is not Encryption. It is not about breaking anything. This is a channel that upposedly does not to allow evasdropping. A completely different thing!

MagiQ - actually building quantum products

[favalora]

Hello - there's a company in NYC and the Boston area actually designing quantum encryption technology for eventual products. They have a team of heavy-hitters in the quantum information world. They're called MagiQ Technologies, Inc.

I know their CEO, and it sounds like they're doing very promising work. They've been pretty quiet about their stuff, but think that it's an example of the real-world applications of this type of technology.

Gregg Favalora - CTO, Actuality Systems, Inc. - The 3-D Display Guys

Particle or wave?

[LeBain]

Does it emit the single photon as a particle or a wave?

Re:Particle or wave?

[AndrewRUK]

Both. All photons (and everything else) is always both a particle and a wave, simultaneously.

Re:although, to be fair

[spankfish]

Humans: just another domesticated animal.

Single photons don't get very far

[Nygard]

I have the same reaction to this as I do to the articles about quantum entanglement.

How the heck are you going to get a single photon to go large distances without getting absorbed? Even in space, if the photon hits a single atom, it will get absorbed, causing an electron to be excited. When the electron "leaps" back to a ground state, emitting a photon, isn't this a new photon?

I would think that this would lose any previously known polarization. If I'm wrong, please explain how a photon retains its "identity" even after being absorbed.

Imagine that this isn't in space, but in the atmosphere. Plenty of matter to interfere with long-range transmission of individual photons. Fiber-optic cables? I dunno.

recent progress

[Hadlock]

there's been alot of progress in LED's as of late, when are we going to see low heat, high light emitting diodes that rival incandecent or florecent lightbulbs? they'd last a lifetime (well, 3 years), and can be of nearly any wavelength...

You're not getting heisenberg's principle

[OeLeWaPpErKe]

it is a TECHNOLOGICAL LIMITATION, it is NOT a fundamental law of physics as you seem to be implying. The only problem is that we need to find something significantly lighter than a photon to detect that photon.

Image the situation like this : we're trying to detect an elephant by throwing elephants at it. Is it any wonder the originial elepant will respond to our "measuring" ? That is the real reason for Heisenberg's principle.

The second we detect an indirect way to detect photons (let's say we detect the gravitational surge) this law will apply only in a much more limited form. There are more than sufficient fields surrounding photons, we just need to build scanners sensitive enough to detect fields that weak (of course without amplifying them)

No

[epepke]

Many people confuse the Heisenberg Uncertainty Principle with quantum entanglement. They're both part of QM, but they aren't the same view of the universe. You could be picky and say that the Uncertainty Principle is an obvious result of basic quantum principles, but it's also the result of some numbers that describe the way our universe is scaled. Anyway, it doesn't say the same thing in the same way.

Public channel, verified identity

[CatherineCornelius]

Actually, you can spoof the two sides. We would break the fiber between Alice and Bob. Handle the negotiation like Bob would when talking to Alice, and similarly handle the negotiation with Bob like Alice would.

Quantum cryptography scenarios normally assume that there exists a public channel upon which Alice and Bob can communicate without the information they communicate being corrupted. The quantum channel is only used for sending uncollapsed wave packets from Alice to Bob, which Bob then collapses in a random manner. They then use the public channel to verify that an untampered communication of data occurred. They just rinse and repeat until the shared key is transmitted.

It's one thing to intercept a closed channel and substitute bad data, quite another to jam a public channel (a radio broadcast, for instance, or a voice call). You could always verify identity using a few bits from the good old one time pad :)

As soon as Alice and Bob are able to confer on the public channel, Eve's intervention will be evident, and they'll just try again until they are able to establish an untampered quantum channel and Alice can communicate the shared key to Bob.

Re:But it may still be hackable

[Grax]

isn't that falling into the 'security through obscurity' trap?

Obscurity is a useful tool. It should never be relied on as a sole defence but then neither should any other security tactic. It should definitely be part of a security admin's arsenal though.

If you disagree then please post your /etc/password and /etc/shadow files for our review.