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Quantum Encryption Via Satellite
Jeff Scarpace writes: "The Economist is reporting that last week, at the International Conference on Quantum Information in Rochester, New York, physicists from the Los Alamos National Laboratories in New Mexico explained how to build a system that will broadcast uncrackable messages via satellite."
But what is the practical usefulness of this outside of the military?
It'll be the end of the DirecTV pirates, anyway.
ABSURDITY, n.: A statement or belief manifestly inconsistent with one's own opinion.
In the fiber-optic version of quantum crypto, each key bit is obtained from alice creating a single photon, measuring it, and sending it to bob to measure. Although I'm sure it's quite tricky, it's not hard to imagine putting a single photon into a fiber, and being able to detect that single photon at the other end.
But how the hell are you supposed to do this via a satellite? I find it simply incomprehensible that a single photon could be successfully bounced off of a satellite and detected when it hit the Earth. Or even successfully shot between two points on the Earth. And if you can manage to send single photons between two points, why not just send plaintext? Sure, someone might tap a fiber without your knowledge. But "tapping" open space without anyone noticing?
Hmmm, boss, there seems to be a van with dark windows parked between alice and bob. Maybe we should stop transmitting? Dont' get me wrong, quantum crypt is neat stuff. And I definitely think it has applications. But not for sending messages thru open space. By the time you have solved the engineering problem of sending single photons reliably over long distances outside, the crypto is meaningless. If you want to see if any one is listening, just look. If your enemies figure out how to make their eavesdropping equipment invisible, you have bigger problems to deal with!
It's 100% unbreakable and available without any high tech satellites.
Want Root?
So, how do you broadcast a single photon everywhere? That's the key. If you send the message everywhere, you are obviously not sending single photons. If you can send a single photon reliably from point a to point b, you have figured out how to make sure it doesn't get lost in between.
... ) are particles fundamental.(Bohmian quantum mechanics is a quasi-exception.)
Though it is too late for this response to make any difference, I'll waste my breath.
Quantum mechanically, a photon is an eigenmode of Maxwell's equations for the system under consideration. A photon is commonly thought of as a localized particle of light. It is not. It is most analogous to a wave (a plane wave is an eigenmode of free space; in a complicated system, the eigenmodes are less straightforeward).
A photon is not localized. A superposition of photons may be localized. Such a superposition is best called a wave packet; it is not strictly a photon though.
Confusion over this is why very few people can actually make sense of quantum mechanics, especially if explained without mathematics (all that non-sensical jibber-jabber about wave-particle duality with bad philosophy thrown in for good measure).
At no point in any quantum mechanical formalism I've seen (Hamiltonian-based, Lagrangian-based, Heisenberg matrix mechanics, Schrodinger wave mechanics, Feynman path integrals, relativistic field theory,
Quantum mechanics is about waves (or more precisely eigenmodes of the Hamiltonian). Superpositions of waves makes particle-like excitations.
So, you can send a single photon everywhere. For a quick example, think of the two slit experiment. It still works when the photons pass through the system one at a time (this has been experiementally demonstrated). Thus, one photon passes through both slits and interferes with itself on the other side.
If photons were localized, as you seem to think, the two slit experiement would fail.
However, producing a single photon is not simple. Devices like lasers will produce a spectrum of photons with a certain narrow energy spread and a certain narrow angular spread. Such superposition of photons will be localized in space and are what people often call photons or particles of light. The probability of detecting such a wave packet in two widely separated places is negligible.
However, other devices (like say an antenna) produce wave packets which are not localized.
And in response to another post:
The reason that quantam[sic] encryption isn't used everywehere, is that it's so darn hard to detect the spin of single photons.
Detecting the spin a stream of photons is much easier than you think. Photon spin and photon polarization are closely related (photon spin is a different set of basis vectors to express photon polarization). Detecting photon polarization is trivial (sunglasses anyone?). Detecting a single photon's polarization with a bit error rate low enough to be usable over long distances is more challenging but not impossible (especially if you are just doing key exchange).
Yes, I have a Ph.D. and quantum electronics is my day job.
Kevin
Take a look at <A href="http://www.counterpane.com/crypto-gram-0103. html#6">the March Crypto-Gram</A>, where Bruce Schneier comments on the practicality of this.
There is a basic result in quantum mechanics called the "No Clone Theorem". It says that there is no device that can be guaranteed duplicate the quantum state of a physical system - even a simple one like the spin of a single electron. (Naively you can think of the problem as being that attempting to clone the state involves interfering with it and hence you risk modifying it - but it goes deeper than that.) The "No Clone Theorem" follows almost trivially from the basic axioms of Quantum Mechanics so that if this is violated then we have a major physics paradigm shift on our hands. Quantum encryption merely exploits the No Clone Theorem.
--
-- SIGFPE
Doing it with a laser over 10km of desert is new. If you can do that then doing it with a satellite seems within reach. So this is fairly significant work.
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-- SIGFPE
Ok. So it's fine to authenticate the source of the transmission, assuming that you only care about the last machine to touch the transmission, but when the transmission passes through multiple machines you can't prove the original source from the data received at the destination. All you can do is hope all the previous connections are trustworthy.
Now how many people here work with a technology that has NO store and forward capability?
No Zen is good zen
Sounds pretty slick, but wouldn't it still be vulnerable if "bob" or "alice" (from the example in the story) left their computer (or other communication device) where other people had access to it?
** The opinions expressed here are my own, and do not reflect those of my employers - past, present, or future**
I'm not talking about simple XOR, where every character is changed by a single amount (which can be solved by running a loop 256 times), but one where each character is modified by a different value, based on a "one time pad" file.
i.e.
Bob, lets kill Joe tonight (message)
a4g6uk98hgdwegfh6532d7ih44 (key, also includes high ascii values which are not here because of the lameness filter)
gregjlghrtg095gjr234fsasdf (result, also high ascii)
I'm assuming, that without the key (or a way to duplicate it), that the message would be "unbreakable", because without knowing the key, there is no real way to decrypt the message - Sure, you can try every possible combination, and even filter out results that don't make sense (or aren't in a dictionary), but there are still thousands of
a four letter word could be
"four"
"kill"
"hell"
"fuck"
"HTML"
"idea"
"hack"
"shit"
"book"
"unix"
"1337"
"them"
"blow"
" bob"
"b ob"
"bob "
etc...
It would seem that the same restrictions apply
PGP users have to keep their private key safe, just as users of this method would have to keep their "key disk" safe.
I belive PGP can be broken with enough time / effort, as could this method, but I belive that there would be a shitload more garbage for people to sort through using this method. Besides, I'm sure that the NSA has some way of reading PGP / whatever encrypted messages already. Seriously, the stealth bomber was designed in 1970, and although it's not the "best of the best", it is still considered an acheivement today, they have some pretty nifty shit somewhere.
The advantages I see to encryption like this are:
- Keydisks can be physically destroyed quickly. Stuff on HDD's tend to stay there, you smash a CD, it breaks into several hundred pieces, tends not to be put back together.
- A message could be one of thousands of the possibilities, and without the key, it would be unknown which one was actually correct. I'm sure you'll get some great works of literature (i.e. monkeys writing shakespeare) popping out.
- With some additional ambiguity, such as codenames, possible translations of the message, padding the message with garbage values, a constant message size, bad spelling, personally giving the disk to the receipient (business card CD's would be perfect for this, although the 8cm ones look a lot cooler for this), etc.... it would seem that this system would be VERY secure.
Of course, there would be no way to prove that you didn't write "bob, lets kill the president tomorow" without handing over the key.
If anyone can help me out / unconfuse me, it would be great... Suggesting some good sources would be great too.
Thanks.
The slashdot 2 minute between postings limit: /.'ers since Spring 2001.
Pissing off coffee drinking
1q2w3e4r5t6y7u8i9o0pqawsedrftgthyjukilo;p'azsxdcf
The communication doesn't have to travel via satellite. The satellite is just used to exchange keys.
Or, in other words, this solves the same problem as RSA and D-H key exchange techniques. Once both sides have agreed on keys, you could use carrier pigeons for the actual excrypted data transmission.
b&
All but God can prove this sentence true.
DW: I never cared much for the term "uncrackable", it seems a bit too much like "unsinkable".
Brigadier: What's wrong with "unsinkable"?
DW: "Nothing," said the iceberg to the Titanic [glug glug glug]
Well, your fingers weave quick minarets; Speak in secret alphabets;
std::disclaimer<std::legalese> sig=new std::disclaimer; sig->dump(); delete sig;
There are two big problems I have with this "new" technology.
1) It isn't anywhere near feasible for common use, nor cheap enough.
2) We already have "pretty good privacy". It's not the best, but it is sufficient and now we need to work on the next big step: securing both ends.
I think we've pretty much covered the encryption news to death and left out some of the big stuff, the compromising of a machine on either end of the communication.
What good does a secure method of communication do when the website you are dealing with stores your credit card info in clear text databases on machines 4 different crackers have access too?
What good is securing a transmission with a customer when their Windows box is already compromised by a Subseven server?
I guess what my biggest beef with secure communication overkill like this is that we've already determined it is possible to secure a transmission. We haven't determined how to properly secure both the client and the server.
methinks I remember an unbreakable cryptosystem, also via satellite. This piece does not mention Professor Rabin.
~
It would be funny if the latest thing in crypto was able to catch the NSA with their pants down.
There are a thousand forms of subversion, but few can equal the convenience and immediacy of a cream pie -Noel Godin
Yet one more reason to procure an aluminum foil deflector beanie; when the aliens, thinking they're helping, begin transmitting quantum-encrypted mind control beams to counteract those of the military-industrial complex, if we don't have adequate protection we'll all go into convulsions, frothing at the mouth as our brains are overwhelmed by gibberish instructions. Society will end as we know it and the forces behind black helicopters and Jimmy Hoffa's unexplained disappearance will emerge from their hiding places to take over the world!
Protect yourself now!
MacOS, Windows, BeOS, GNOME, KDE: they're all just Xerox copies
The reason that quantam encryption isn't used everywehere, is that it's so darn hard to detect the spin of single photons. I think it's extremley unlikley that they have figured out how to discern the spin of a stream of photons, over 10 kilomiters, with a 0% error rate (otherwise you've got a bad encryption key) when it can barely be done over inches. That being said, it's still only a secure (YES, 100% Unbreakable, unless you feel like violating the laws of phyisics) method of exchanging encryption keys, but once exchanged, the data is still vulnerable to brute force cracking, like distributed.net.
The (Hopefully) Great Slashdot Blackout Apr 21-27
when aliens finally do intercept our transmissions they will think we all speak giberish.
While this kind of quantum cryptograhy has been around for awhile, the article is correct in stating that such expiraments have only been done across wires until this point. The really neat thing about this is that it really is safe. These technologies do not rely on security through obscurity in any way. The key is sent quantumly, and cannot be intercepted without breaking the quantum entanglement of the particles. Once a secure key has been transmitted, it does need to be protected within the software, but that is much easier than protecting is as it flies through the air. The security of the key as it is transmitted is protected by the laws of physics, which is what makes this so secure. While there is no silver bullet to the problem at hand, this solves fundamental problem of keys being sniffed during transit without anyone knowing. From here there are a lot of other problems to solve, but its a big step toward secure transmissions in the open.
Windows is more convenient than Linux just as having an ingrown toenail is more convenient than seeing a podiatrist.