Slashdot Mirror
Quantum Cryptography Gets Nanotube Boost
c1ay writes "In an article at the ScienceDaily News it is reported that two researchers at the University of Rochester have discovered a new property of carbon nanotubes, ideal photon emission. "The emission bandwidth is as narrow as you can get at room temperature," says Lukas Novotny, professor of optics at Rochester and co-author of the study. Such a narrow and steady emission can make such fields as quantum cryptography and single-molecule sensors a practical reality. RSA and Elliptic Curve wouldn't stand a chance against this unbreakable encryption."
When will they have a quantum encryption cracking competition? Go Team Slashdot!
Any cryptographer would know that.. it just might take 10^19 years to crack a key!
they discovered this interesting phenomenon while playing with their bucky balls.
Want to improve your Karma? Instead of "Post Anonymously", try the "Post Humously" option.
Nanotubes Surprise Again: Ideal Photon Emission
Sept 5, 2003 -- Carbon nanotubes, recently created cylinders of tightly bonded carbon atoms, have dazzled scientists and engineers with their seemingly endless list of special abilities--from incredible tensile strength to revolutionizing computer chips. In today's issue of Science, two University of Rochester researchers add another feat to the nanotubes' list: ideal photon emission.
"The emission bandwidth is as narrow as you can get at room temperature," says Lukas Novotny, professor of optics at Rochester and co-author of the study. Such a narrow and steady emission can make such fields as quantum cryptography and single-molecule sensors a practical reality.
The emission profile came as a surprise to Todd Krauss, assistant professor of chemistry at the University, and Novotny. They had set out to simply define the emission, or fluorescence, of a single carbon nanotube. By using a technique called confocal microscopy, the team illuminated a single nanotube with a strongly focused laser beam. The tube absorbed the light from the laser and then re-emitted light at new frequencies that carried information about the tube's physical characteristics and its surroundings.
The light emitted from the nanotube was in precise, discrete wavelengths, unlike most objects like molecules that radiate into a broader (i.e. more "fuzzy") range of wavelengths at room temperature.
But a greater surprise was in store for the team.
"The emission wasn't just perfectly narrow, it was steady as far as we could measure," says Krauss. In a strange quirk of quantum physics, molecules usually emit their photons for a certain time and then cease, only to resume again later, like a telegraph signal. The tubes that Krauss and Novotny measured, however, remained steady beacons to the limits of their instruments' sensitivity. "This is very exciting because for any application in quantum optics, you want a steady and precise photon emitter," says Novotny.
Narrow emissions and a complete absence of blinking have tempting implications for single photon emitters--devices needed to dependably release a single photon on command. The U.S. Department of Defense is very interested in developing quantum cryptography, a theoretically unbreakable method of coding information, which necessitates a reliable way to deliver single photons on demand.
Other applications come in the form of sensors so sensitive they can detect a single molecule of a substance. For example, when a biological molecule such as a protein binds to a nanotube, the nanotube's perfect emission changes, revealing the presence and characteristics of the molecule. Detecting the change would be impossible if it weren't for the remarkably steady nature of the nanotube emission, because a researcher wouldn't know for certain if a sudden change in the emission was just a blink, or was meant to indicate the presence of the target molecule.
Until just a few months ago, determining the emission characteristics of a nanotube was impossible. Carbon nanotubes cannot be made individually-rather they come as a jumble like a pile of spaghetti. Trying to measure the photon emission of a tube in the jumble is impossible because the tube will pass the photons it absorbs to other tubes instead of re-emitting them in its telltale fashion. What scientists end up with is a sort of average of what the collection of tubes will emit--not the emission characteristics of a single tube. Only within the past few months have researchers figured out how to remove a single nanotube from the pile of spaghetti in order to study its properties as an individual.
Krauss and Novotny are now devising experiments to test the steadiness of the nanotube fluorescence beyond the range of the initial experiments, and are pursuing studies aimed at determining the ultimate minimum possible emission bandwidth at ultracold temperatures.
This work was funded by the National Science Foundation, the U.S. Department of Energy, the Research Corporation, and the New York State Office of Science and Academic Research.
Editor's Note: The original news release can be found here.
This story has been adapted from a news release issued by University Of Rochester.
http://www.cs.dartmouth.edu/~jford/crypto.html
http://www.aip.org/pt/vol-53/iss-11/p22.html
Mostly a theoretical breakdown of the advantages of quantum encryption, in fairly easy to understand language.
From NCBI.
Single-walled carbon nanotubes (SWNTs) are synthesized as mixtures of metallic and semiconducting tubes (1). Their individual structures can be characterized by two integers [(n,m)] that define both their diameter and chirality (2); if (n - m) is not divisible by 3, the nanotubes are semiconducting. Recently, the photoluminescence of SWNT mixtures suspended in surfactant micelles in water was characterized as arising from band-gap fluorescence from semiconducting tubes with different structures (3, 4). Such a spectrum (Fig. 1A) (5) contains overlapping fluorescence features. However, ensemble averaging obscures the true spectral linewidths and the details of the band shape. These optical properties are likely needed for the development of SWNT photonic applications, such as nanometer-scale, integrated electroluminescent devices (6).
We measured the electronic structure of individual SWNTs using single-molecule photoluminescence spectroscopy. Although the spectra from individual SWNTs with identical diameters were similar, they exhibited a distribution of peak positions and linewidths not observed in ensemble studies of isolated SWNTs (3, 4, 7). Unlike most single molecules (8) or semiconductor nanoparticles (9), the fluorescence for SWNTs does not show any spectral or intensity fluctuations.
Spatially isolated individual SWNTs were achieved by spin-coating 75 l of the SWNT suspension onto a glass coverslip (5). Fluorescent samples are known to contain short (200 nm long) SWNTs isolated in micelles (3). Thus, we expected the spin-coating procedure to result in single SWNTs well dispersed on a thin surfactant layer. Indeed, atomic force microscopy measurements revealed predominantly short SWNTs (with lengths of 200 to 300 nm) on top of residual surfactant patches a few nanometers thick. Optical characterization of SWNT coverage was achieved through confocal Raman imaging (10, 11) and indicated a density of 10 to 20 Raman-active nanotubes per 100 m2. Laser excitation at 633 nm ensured a spectral isolation of all Raman signals, which occur between 633 and 770 nm, from the fluorescence signals above 850 nm.
Figure 1B shows three fluorescence images of the same sample area, representing the collected number of photons at every pixel within the spectral windows marked in Fig. 1A. All images show distinct bright spots at different positions, indicating isolated emission sources with different emission energies. Figure 2A displays representative spectra detected at these bright spots for the three wavelength regions marked in Fig. 1. Each spectrum exhibits a single fluorescence band with a smooth line shape. The three spectra have emission maxima at wavelengths of 1016, 955, and 914 nm, respectively, which match three transitions observed in the ensemble spectrum (Fig. 1A).
Low-energy Raman features that correspond to scattering from the radial breathing mode (RBM) were used to verify that the observed emissions were from individual SWNTs. Raman spectra (Fig. 2B) were detected at identical sample positions (noted in Fig. 2 as 1, 2, and 3) as those used to obtain the fluorescence spectra in Fig. 2A. The frequency of the RBM (, in cm-1) directly reflects the diameter of the SWNT (D, in nm), through = (223.5/D) + 12.5 (4, 12), and can be used to uniquely identify the structural parameters (n,m) (13). For all three sample positions, only one RBM peak (corresponding to the same individual SWNT) was observed within the instrument-limited linewidth of 10 cm-1.
The observed emission energies and corresponding RBM frequencies are listed in Table 1, along with values obtained from fluorescence of ensemble samples (4). Nanotubes with emission beyond 1030 nm will not be observed with our detector (Si CCD); thus, we can compare single nanotube fluorescence and Raman RBM data sets to ensemble data sets for a subset of all possible nanotube structures (Table 1). The mean measured fluorescence energy for a given SWNT structure (supporting online text), for resonant and nonresonant excitation, matches very
word
When will they invent something faster than the speed of light ? It's 2:23am and I still can't get a first post because of the latency!
So-called "quantum encryption" may be unbreakable, but it is ignorant to portray it as a competitor to something like RSA. Quantum encrypton is a link-layer technique - something one would use to prevent eavesdropping on a single fibre hop (which is hardly a problem anyway).
Worse, it is hardly practical for real networks anyway - with routers, repeaters, EBFAs or Raman amps everywhere. If it ever makes it out of the lab, it may be useful for military systems (where money is no object), but it won't help you pirate music anonymously.
Hmmm, I bet we will be soon buying Carbon Nano Tube Protected(C) music. It won't play in some CD players, but the discs will be clearly labeled so we, the customers, won't be wasting our money.
Wouldn't that be GARIAAA?
RSA and elliptic curve are able to provide encryption safe from a man in the middle attack, as well as authentication of where a message came from (signing). This is far ahead of what quantum encryption offers.
The only security quantum encyption has is that the message can only be read by one viewer - this prevents covert surveillance of the message, but not a man in the middle attack, nor a total interception.
Pragmatically you bundle quantum encryption with other authentication techniques, but RSA on it's own is far more useful and secure than quantum encryption on its own.
It's not time to throw RSA and Elliptic curve out just yet.
And crackers don't really stand a chance against the algorithms we have now. Although I'm happy to see them inventing cool stuff and cryptography os definitely neat, will this makes us more secure? Sure computers keep getting better and you need to stay ahead of the curve if you are someone like the NSA, but are people the loosing the security game because their 128 bit RSA keys keep getting cracked ? No. They are insecure because they have nanotube-size brains and use their birthday for their password or they leave a laptop with the vice president's agenda at a convenience store.
What we normally mean by "encryption" is "the transformation of readable stuff into stuff that can be seen by evil people without them able to understand anything". Encrypted data are a stream of bits just like anything else. Thus you can store your encrypted message on a disk, or write it down, or transmit it over a wire, or broadcast it.
In this sense "quantum encryption" isn't encryption at all. Quantum encryption is something that can only happen as part of the act of transmission. There is no such thing as "quantum-encrypted data" that can be recorded or written down or transmitted over conventional media. The act of doing any of those things collapses the wave packet and destroys communication just as effectively as interception would.
I'm not going to argue that we should start calling quantum encryption something else, the name is too snappy and too useful for getting research grants, but let's not get confused into comparing it with public-key or even private-key encryption: they're completely different animals.
RSA and Elliptic Curve wouldn't stand a chance against this unbreakable encryption.
Huh? Are RSA and Elliptic Curve some method for breaking encryption? Yeah I know what he meant, just worded funny.
I.O.U One Sig.
I thought Elliptic Curve only existed in Uplink until I read this article :p
Founder of Mirror Moon - Tsukihime Game Trans
GARIAA
<BR>
That sounds like some new form of VD or something.
They kinda suck as straws. Well, they don't really suck, but thats the problem.
According the the Sep. 6th issue of The Economist there is a company in Massachusetts called MagiQin the final stages of testing a system which it plans to release commercially in the next few months.
"The scheme devised by MagiQ, called Navajo, does not use quantum effects to transmit the secret data. Instead, it is the keys used to encrypt the data that rely on quantum theory. If these keys are changed frequently (up to 1000 times a second in Navajo's case), the risk that an eavesdropper without the key would be able to decrypt the data can be proved mathematically to be zero.
mathematically unbreakable.
but we've heard that before.
"Just add another wheel to the Enigma machine Hermann. Those dim-witted English shopkeepers vill never figure it out... "
Quantum cryptography is very interesting--an absolutely bizarre manifestation of one of the most spooky and anti-intuitive features of quantum mechanics. The very premise gave Einstein fits.
But where RSA is used (and, barring an as of yet undiscovered in the open world weakness, elliptic curve cryptography) quantum cryptography has no application.
Quantum cryptography is built on the quantum entanglement of photon pairs, who's wave function must remain un-collapsed by measurement or perturbation until decode. This feature is both quantum cryptography's strength and weakness:
It's a strength because any Eve eavesdropping is irrefutably revealed.
It's a weakness because it limits the applications to such Alices and Bobs where between actual original photons may be reliably transmitted.
RSA and various other "Newtonian" cryptographic schemes make use of mathematical transforms rather than physical properties of individual particles and survive re-transmission with their essential properties intact; for example, over a packet switched network.
What RSA may not ultimately stand a chance against are quantum computers, which according to a variation of Moore's law I might have been the first to state (at DEFCON 9), will within a decade surpass then available classical computers and will (in theory) be exceptionally good at cracking encrypted documents.
Assuming the NSA doesn't already have a good working quantum computer...
And assuming it's possible to continue adding entangled qubits...
Anyway, Moores law says the power of classical computers increases as 2^(Y/1.5), where Y is years. So far, roughly, quantum computers are increasing in power as 2^2^(Y/2), which should make em about 10^225 times as powerful as today's classical computers in 2 decades, and if that turns out to be so, then RSA really won't stand a chance. It might be a bummer for some: 4096 bit PGP keys are assumed to be safe against, for example, the combined efforts of all computers to be built according to Moores law between now and any normal lifetime, or at least well past the statute of limitations. But if quantum computer development continues apace, that assumption may be problematically flawed.
But it's not quantum encryption that's the threat, it's quantum computers. Quantum encryption isn't any more unbreakable than whatever data method underlays it, though it's a fine way to transmit a stream of random numbers. The "key" is that it is, apparently, physics-ally impossible to intercept the stream of photons without causing a measurable effect. So Alice and Bob can be absolutely sure their one time pad is known only to them...
as long as no one is looking over their shoulders...
Now we are one step closer to giving people the false impression that they can be idiots with their data because this particular magic bullet (QC) will be completely secure.
All this talk about cryptography sure is sexy, but how about something practical, like a computer monitor with resolution so high you can't even see the pixels? I want a screen that is indistinguishable from a sheet of paper.
But can they stop the viagra and enlargement ads?
Could they be programmed to tunnel through the Internet, seek out and bind to the sender in a way that makes them instantly the most attractive object to, say, any and all lightning discharges within a 1000 mile radius - it would look kinda like Neo when he took the red pill and then looked in the mirror.
Bwahahahaha
AT&ROFLMAO
Back when high-bit encryption was becoming popular, there was a great effort on the part of the government to control its use, especially the "export" of encryption technology.
With the advent of unbreakable quantum encryption, we are clearly in for more of the same. If you think the line at the arirport is long now, just wait until security starts searching people for nanotubes. Me, I'm seriously considering driving everywhere.
RSA and Elliptic Curve wouldn't stand a chance against this unbreakable encryption
Oh yeah, that cheap and easy cryptography technology that can be performed on a CPU in a wristwatch or smartcard and be can used for encryption, signing, PKI infrastructure, n of m schemes etc will be instantly replaced by a system that's only good to transmit bits with a guarantee that the recipient will be able to detect if someone else is reading the traffic. Yawn.
"Mary had a crypto key, she kept it in escrow, and everything that Mary said, the Feds were sure to know."
Straws dont suck. people do.
what's a quantum computer?
Thanks!
Sivaram Velauthapillai
Sivaram Velauthapillai
Seeking the meaning of life... @slashdot of all places
There is some reason to suspect that quantum states are transmissible from one photon to the next ad infinitum. (Don't forget that all forms of data transmission involve direct physical linkage, even in the form of waves.) I would not rule out the ability of future quantum computers to be able to suss out such subtle states by the use of markers in data. Given the metaphysical interconnectedness of all matter / energy it would be fairly impossible to prevent "leakage" from occurring. But generally speaking, outside of a given quantum communication system information will be quickly obscured by the background noise of the physical universe. Still, as quantum snooping computers evolve more sophisticated forms of quantum encryption will become necessary.
Of course this sense comes from a very crude understanding of quantum mechanics, so feel free to deride my Star Trek-ish scientific sensibilities.-- thinkyhead software and media
they make lousy spel chekers
Quantum cryptography is a method for using quantum physics to make sure nobody reads your bits. Technically cool, but seldom practical. If you happen to have direct fibers connecting you with the people you want to talk to, it might be useful, though it's probably more useful and certainly cheaper to just run Gigabit Ethernet and use conventional encryption, such as AES.
Quantum computing is a totally different animal. It uses Quantum Black Magic to create a computer which can collapse a waveform and have it land at the solution of some classes of NP or similarly problems with at least some significant probability of success, thereby cheating on the fact that it normally takes an exponential or at least superpolynomial number of guesses to find a correct answer. One problem that can theoretically be solved if you have a quantum computer of sufficient resolution is factoring - which means that if such a device were developed, it would break RSA and several other public-key algorithms, whose strength depends on them being exponentially hard if you don't have the key and low-order polynomially hard if you have it. For some other classes of algorithms, it doesn't totally break them, but reduces their strength to half the number of bits, i.e. square-root as hard as before, so you'd need to use twice as many key bits. For algorithms like Elliptic Curve, it's not clear whether they'd be broken, but they'd be a lot more dodgy.
The implications of breaking them are that right now, public key lets you build a lot of very useful communication models. It's hard to replicate signatures without PK, but the privacy applications could be replaced by going back to the old Key Distribution Center models, e.g. Kerberos, which are much less socially powerful.
Building a useful quantum computer requires building something that can detect states with sufficient precision. We currently have the technology to make simple quantum computers (one famous one was able to factor the number 15 into 3x5) but nobody knows how to get high precision yet. One question I don't know is whether a QC would be limited by the Heisenberg Uncertainty Principle (i.e. you've got one variable with a resolution that's never better than Planck's Constant, about 10**-47, which is slightly annoying cryptographically but not fatal because you can use longer keys), or whether it can be built by coupling together a number of units, each of which only needs enough precision to get N bits of the output and you get longer numbers of bits by using more units (that would be much more annoying.) We're nowhere near this yet, but it's the one technology that doesn't run into the typical exponential cryptography "brain the size size of the planet of a planet waiting for the Restaurant at the End of the Universe and still don't have an answer, I'm so depressed" kind of limits that we can easily create otherwise.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
Exactly. The mathematical analysis performed by Enigma's designers did not include variables for the number of times the secret codebook would be stolen by the enemy, the number of daily communications reporting more or less the same thing (weather conditions) which make the task of finding embedded patterns possible - and sometimes easy. They did not they consider the constuction of the Bombes...
Most of all, the designers (and users) of Enigma underestimated the capabilities of their enemies because they did not know what they were capable of.
My point was that the clever way in which quantum crypto WILL be cracked have not been conceived yet so it seems to me impossible - based on today's understanding of the problem - to perform a valid mathematical analysis.
Not all of the variables are known. Or as Donald Rumsfeld so eloquently said it:
The Unknown
As we know,
There are known knowns.
There are things we know we know.
We also know
There are known unknowns.
That is to say
We know there are some things
We do not know.
But there are also unknown unknowns,
The ones we don't know
We don't know.
--Donald Rumsfeld, Feb. 12, 2002, Department of Defense news briefing
My $.02
All this cryptography sounds cool and all, but will we even get to play with it? I mean, at first good ole Uncle Sammy had fits about the common man having high encryption, and it is still illegal to export it. With encryption as good as this quantum, would Uncle Sam even let us use it? I mean, if it really were unbreakable, then the UnPatriot act would be kinda limp...
Why oh why didn't I take the purple pill?
While we're on the topic of cryptography and RSA and stuff, does anybody know what happened to 'Operation Project X'?
http://www.operationprojectx.com/
They were attempting to factorize the xbox public key to break the RSA encryption used. I can only guess they were closed down...
---
Any man who can drive safely while kissing a pretty girl is simply not giving the kiss the attention it deserves. -- AE
Only within the past few months have researchers figured out how to remove a single nanotube from the pile of spaghetti...
Maybe they should start eating their lunch outside of the lab.
Man, talk about a needle in a haystack!
Can anybody comment on whether this new result applies to generating single photons?
Noone has ever created a One time Pad plugin for outlook.
Think about it. Create a random one time Pad of a few hundred MB. Burn it on 2 cd-r. Put one in your safe and hand the other to BOB in person.
Now just use the pad piece by piece for your secure transmissions. It should last for years if you dont sent porn or warez....
As long as you use every part of the pad only once, even if the attacker gets the plaintext of one message the others wont be compromised.
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
This technology looks to be to expensive today and in the future days for any of your wallets. Here is my solution to getting true randonm numbers. Get pre-schoolers to work their majic with assorted high grit crayons on gloss paper in predefined boxed sections. Then use a scanning microscope to probe the abnormal surfaces with precise nano depth rendering feedback to a commodore 64.
AceiI
Wait till they start putting them in shampoo and ati-wrinkle cream.
...and he grinned, like a fox eating shit out of a wire brush.
I still haven't managed to get a date by using nanotubes.
Way to go, nanotubes.
- "They misunderestimated me."
I am wondering what will happen with security everywhere when quantum computers step into every day life. Classic methods like RSA will be solved in a minute. What about quantum cryptography ? does it stand a chance against quantum computers ? and what will be the effect on society, if nothing can be encrypted any more ?
i don't know if you know this, but that's not how encryption works... :)
Just raise the taxes on crack.
That's a really big ASSumption.
Don't forget the other ASSumption, that you can maintain the quantum states long enough to do useful computations with them. OK, perhaps some day, but not in 10 years.
We'll have to go right to...
ludicrous speed!
All I need now is "String Theory" and I win!
"Studies have shown that people who eat peanuts live longer than those who do not eat."
How about a non-terminating, non repeating decimal expansion of a number? Pi? sqrt(2)? The square root of 2, in particular, has been shown to be an irrational number. This means that it cannot be written as the form m/n, where m and n are integers.
This means that it can't be repeating (0.454545... = 45/99) and it can't terminate (0.3453 = 3453/10000). This was proved back in pythagorean times (second yellow box as you scroll down the page).
Note that most square roots, cube roots, 4th roots, etc are going to be irrational. Is that a big enough choice of random OTPs for you? Say only a tiny fraction of numbers are irrational. A tiny fraction of an Aleph-one infinite numbers is still infinite. (See degrees of infinity, about halfway down the page).
It may look like I'm doing nothing, but I'm actively waiting for my problems to go away.
--Scott Adams
Kind of.. rolls off the tongue, doesn't it? Just imagine System of a Down saying it: "Ga-rye-ahahah!"
That's my school! You go boiii!
Moore's law says that computers get faster exponentially (2^(Y/1.5)). That's bad news in the long run for any theoretically breakable scheme. The only answer for today's technologies is to be continually increasing the key size to keep up with Moore's law.
And another thing: If we're at all worried about the NSA being able to break our commonly-used encryption methods, then shouldn't we be using significantly higher key sizes right now?
What key size would convince the experts that the NSA would not be able to break encryption at today's computer speeds? 512 bits? 2K bits? What is preventing us from embracing those larger key sizes for applications that are not as performance critical (such as email)?
The poster is, in the main, correct in his ASSertation, but there are underlying justifications to the extraction:
First, classical computers may, to a crude degree, be considered "powerful" as a function of their clock speed and complexity. Roughly this power has been increasing at an exponential rate according to "Moore's Law."
Quantum computers are entirely different in a way that matters for certain classes of problems, particularly sorting and testing. These classes of problems are well suited, for example, to "brute force" breaking encryption. A quantum computer's "power" in solving this class of problem increases to the power of the number of "entangled cubits", a number which has roughly doubled every two years as compared to Moore's 18 month period - and to classical computing's roughly linear increase in power with complexity.
Moore's "law" isn't a law at all, but has been useful in predicting computational power. This reformulation I propose is valid in hindsight over a trivially short observation period. It does seem like a useful exercise to think about the potentials of quantum computers and to make a "what if" sort of assessment of the future of computing.
The statement that only a few quantum transistors have thus far been assembled, is not entirely true. First, the computational structures of quantum computers and classical computers are not precisely analogous, second quantum computers have been used to perform calculations according to prediction in organized structures more complex than an equivalent "transistor."
http://arxiv.org/abs/quant-ph/9801037
Unbreakable? Don't be so sure of yourself, Mr. Titanic. I guarantee that this encryption method, like any other, will be "broken" in time. It may not be cracked in the way you're thinking of, but mark the words of the great AC, it will be broken.
tape their passwords to their monitors.
Shop smart, Shop S-Mart.
-this unbreakable encryption. It'll be unbreakable until microsoft gets it's hands on it and creates a bug that lets you break it in five minutes. Or until we get quantum decryption.
"For years, I struggled with reality... but I'm happy to say I finally won out over it." -- Elwood P. Dowd