Quantum Cryptography Broken, and Fixed 118
schliz writes in with research out of Sweden in which researchers showed that, looking at a quantum cryptographic system as a whole, it was possible for an eavesdropper to extract some information about the QC key, thus reducing the security of the overall system. The team then proposed a cheap and simple fix for the problem. "The advanced technology was thought to be unbreakable due to laws of quantum mechanics that state that quantum mechanical objects cannot be observed or manipulated without being disturbed. But a research team at Linköping University in Sweden claim that it is possible for an eavesdropper to [get around the limitations] without being discovered. In a research paper, published in the international engineering journal IEEE Transactions on Information Theory (abstract), the researchers propose a change in the quantum cryptography process that they expect will restore the security of the technology."
So is the cat dead? (Score:5, Funny)
Re:So is the cat dead? (Score:5, Funny)
Which is precisely what happened.
By being sufficiently precise about the nature of the insecurity, they changed the probability of its being insecure!
Furthermore, now that we know it's secure again (that is, we've proven it to be secure, effectively computing the probability of insecurity to be precisely zero), we no longer know anything about the nature of the system's security holes again!
That was all supposed to be a lead-up to a Heisenberg Uncertainty Principle joke, but it's actually a pretty good description of how computer security works in even the non-quantum world. The more secure you think your system is, the more likely it is you'll get 0wn3d in some completely unexpected way. The known unknowns aren't the ones you've gotta worry about, and nailing them down doesn't do anything about the unknown unknowns, other than to collapse the joke's waveform into something resembling a Don Rumsfeld speech.
In anything other than a Slashdot quantum crypto discussion, that sort of whiplash-inducing change of joke subjects would be highly improbable. As it stands, I'm going to shift gears a third time and hand it off to Douglas Adams.
Zaphod: Tackhead, is this sort of thing going to happen every time you post using the Infinite Improbability joke drive?
Tackhead: Very probably, I'm afraid.
Re:So is the cat dead? (Score:5, Funny)
It can be either alive or dead or both alive and dead.
We call these three states alive, dead and zombie.
There, I hope that sheds some photons on the matter.
Re:So is the cat dead? (Score:5, Funny)
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Actually, "high-impedance" is how'd I'd describe the alive state for most cats - yikes!
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Re:So is the cat dead? (Score:5, Funny)
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To quote one of my favorite games [kingdomofloathing.com]:
The cat looks up at you and, noticing a certain hungry gleam in your eye that it doesn't like one bit, jumps from the divan and hides in a box under the coffee-table. Just before the lid clicks shut, you see a tiny pendulum inside, and wonder if the cat's going to be alive for much longer. You reason that, since the cat could be either alive or dead, and you can't know which without opening the box, then therefore the cat must be both alive and dead -- or in other words, undead. That must be what funerals are for -- so that everyone knows for certain that the person going into the coffin is definitely dead, and you don't have to worry about quantum uncertainty causing zombies to burst out of the ground.
Re:So is the cat dead? (Score:4, Funny)
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From Wikipedia [wikipedia.org]:
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Re:Wah? (Score:5, Interesting)
Well the worst thing about an encrypted stream is that you trust it, not really knowing if someone is listening half way down the line. If you get a hint that it's being listened to, you can start sending garbage (or misinformation) down the line so as to confuse the hell out of the eavesdropper, whilst taking up alternative methods of communication or something.
This makes me wonder if cryptography needs to become cleverer. I mean, depending on the type of data you're sending, might there be a role in padding encrypted streams with 'honeypot' data, like random bits of vaguely interesting crap that the expected listener might want to be interested in. Sort of a live equivalent of Truecrypt's plausible deniability.
What do people think about that?
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Now, I admit I don't know that much about cryptography and this probably couldn't ha
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But seriously, there is a good reason unfortunately I haven't yet taken enough physics to adequately understand it much less explain it.
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Re:Wah? (Score:4, Informative)
2. Bob reads the key, but, due to the random encoding, he can read only half of it (you can read only if the receiver is in the same state as the sender), so Bob sees some random subset of the bits. This random subset is the key. Alice does not know which subset this is.
3. Bob transmits the configuration he used to read the stream back to Alice. Alice compares the configuration to her own configuration for sending data and derives which bits Bob saw. They now both know the key.
It is impossible to read the bits without changing them, in which case Bob will see something different from what was sent, so the keys won't match.
It is also impossible to derive the key from the configuration that is sent back by Bob because it only specifies how the bits were read, not what the bits were.
This is, of course, vulnerable to a man-in-the-middle attack, however.
Re:Wah? (Score:4, Informative)
When Eve reads the message changes to 50% correct, 50% incorrect.
When Bob gets the photons his 50% will consist of 25% correct and 25% incorrect ones. (assuming true randomness)
When Alice and Bob compare there keys they will see the discrepancy.
Then the 1 and 0 are XORs with the message and then the result is sent.
http://en.wikipedia.org/wiki/Quantum_cryptography#Polarized_photons_-_Charles_H._Bennett_and_Gilles_Brassard_.281984.29 [wikipedia.org]
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I know the solution (Score:5, Funny)
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http://article.gmane.org/gmane.linux.debian.security.announce/1614 [gmane.org]
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I lol'd really.
There is no such thing as absolute security (Score:4, Insightful)
As long as there is even one access method there exists the opportunity to expoloit it somehow.
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That is why i save all my documents into /dev/null, and read them from /dev/urandom.
By the way, my documents don't seem to like me very much... Am I feeding them wrongly?
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As long as there is even one access method there exists the opportunity to expoloit it somehow.
No. In Mathematics, 1 + 1 = 2. It doesn't just usually equal 2, except in cases that you can't think of right now. Similarly, the computer program:
x = 0
x = x + 1
We know with absolute certainty that x = 1.
Returning to access methods, you need to parse the requested object and retrieve it from storage. For both of those operations it is possible to break them down into simple, irrefutable steps much like x = x + 1 amd prove conclusivly that the program has no security flaws.
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In theory, yes, x will always be 1. However, there are a number of practical cases which can screw this up, since the computer is a mechanical device. For example, cosmic radiation can flip one of the bits in the memory location x was being stored in after it's assigned 0 but before the addition takes place, which can cause a dramatically different result. More realistically, you could have multiple threads running at once and you could be preempted anywhere (including in the middle of that addition) betwee
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I'll ignore threads - it's hard enough to prove a simple deterministic program is correct so I'll assume that this is running without an OS.
As for bit flips due to cosmic radiation, there are plenty of algorithms that ensure a bit hasn't been flipped in a transmission and I would suspect they could be applied to a situation like this. Google pops up helpful hints too, e.g. http://csdl2.computer.org/persagen/DLAbsToc.jsp?resourcePath=/dl/mags/co/&toc=comp/mags/co/2002/01/r1toc.xml&DOI=10.110 [computer.org]
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Yes, but AFAIK quantum cryptography is not about storing and later retrieving data, it is about communicating data between two parties. AFAIK it simply lets the sender and recipient to know if anyone else besides them got the data. From there it is a simple matter of using an inse
That wacky quantum cryptography (Score:5, Funny)
Re:That wacky quantum cryptography (Score:5, Funny)
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Re:That wacky quantum cryptography one in a (Score:1)
Fundamental Flaw in Quantum[Anything] (Score:1, Interesting)
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"I don't believe.."
How about some thinking, eh?
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From superconductors to Aspect experiments
BTW a Superconductor doesn't lose energy because QM makes it impossible for the electrons to scatter of the nuclei. Again something entirely impossible according to our common intuitions, which, alas, the world does not care about all that much.
See also:
http://en.wikipedia.org/wiki/No_cloning_theorem
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If something already makes sense then there is less of a need to study it scientifically. So science will gravitate towards non-intuitive things like neutrinos, recessive genes, bose-einstein condensates, etc.
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I just hope this doesn't catch on..
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Too late, it caught on long ago. It's called religion.
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there's no empirical evidence that proves that he's wrong. and as long as there isn't, he's free to believe what he wants.
Spooky Decryption (Score:2, Funny)
Schroedinger's Key (Score:2)
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I can safely exchange a key, because I can detect eavesdroppers and replace the sniffed parts of the key with new ones?
But if someone is continuosly does that, doesn't he effectively prevent me from communicating at all??
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Article is a dupe... (Score:5, Informative)
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Initialization vector (Score:3, Informative)
"The researchers propose an additional, non-quantum exchange of a small amount of random bits that are separate from the quantum key."
The End of The Science of Cryptography (Score:5, Informative)
This in effect means that the science of cryptography has met its end in terms of development.
Like the game of checkers, there are no more moves to make.
At the time of publication (2002?), the longest distance an encrypted quantum message sent and received was approximately 50kms and considered to be impossible to break.
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Unless of course (as was pointed out above), that lan is using Shrödinger's cat-5...
tm
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Wireless communications are not fundamentally incompatible with Quantum cryptography
No, not really (Score:5, Insightful)
Do you understand that one crucial aspect? If I want to talk to you completely securely, with quantum handshake, and able to detect eavesdroppers, I would need one uninterrupted strand of fibre from Germany to wherever you are. Screw 50kms, we're talking potentially tens of thousands of kilometres.
Or a chain of routers along the way that we both trust blindly to not be compromised, because each breaks that quantum handshake, and each is a point where someone could eavesdrop. You can't tunnel QC over such a hop, so it's a bit like having SSL only from your computer to your ISP, then have it decrypted there and re-encrypted to the next hop, and so on.
It's also pretty much against the whole idea of a network like the Internet. Since again, it needs dedicated uninterrupted point-to-point connections, not a loose mesh of routing machines. (You _could_ transmit the rest over the internet once you negotiated a key over QC, but: 1. you still need a dedicated connection for that handshake, and 2. you still need normal cryptography for the actual transmission then.)
For two John Does like us it's already pretty infeasible to go QC all the way.
Even for someone like the US Army:
1. Good luck having an all-QC connection from Washington to Baghdad. Even in 50 km segments, you need a lot of basically routers every 50 km on the ocean floor, each of them being a potential eavesdropping point. So if you ditch normal cryptography, you'd need to do... what? Park a couple of submarines near each of them to make damn sure the Russkies and Chinese don't tamper with them? Have permanent manned bases on the ocean floor every 50 km, with a company of soldiers watching each router, and watching each other so none of them can be a double agent and tamper with it?
2. And what do you do if someone drops a depth charge on one of those? You sure you don't want some regular crypto as backup?
3. That still doesn't help your communication to your airplanes, tanks, cruise missiles, etc, there. You can't tie a cable from each of them to Washington.
Etc.
So basically... well, let me put it mildly: I don't know what book you've read, or by what author, but I'd bet it wasn't written by someone who knows much about cryptography. It sounds more like the kind of predictions made by self-styled "pundits" like Cringely or Dvorak. Or, of course, any other of the many like them.
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As you might expect, the protocol f
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Only way I could see to MITM attack it would be to put a blimp drone or maneuver a satellite between the two.
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There is the potential to have secured pad generation links which you could take your keys away from and then encrypt over the recular internet.
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Oh, (Score:3, Funny)
Alice and Bob are sick today. We need some answers (Score:4, Funny)
Re:Alice and Bob are sick today. We need some answ (Score:4, Interesting)
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Re:Alice and Bob are sick today. We need some answ (Score:1)
In a sense.
A number of Polarised photons are sent.
The person receiving uses one of 2 filters/readers .
Use the right filter and you get the correct bit.
Use the wrong filter and half of the time you get the correct bit and the other time you get the wrong one. This means if you incept the key you can not send the same set of photons on.
Discard the ones that you used the wrong filter on and then compare your key with the other person. (over an un-encrypted line). If there are too many errors then it
Re:Alice and Bob are sick today. We need some answ (Score:1)
a one-time-pad is unbreakable but needs keys to be distrubted.
QC is used to send the keys and if it is incepted it can be detected and the key discarded.
I've made one other comment on Slashdot, but... (Score:1)
Broken QC FAQ (Score:3, Informative)
Re:One time pad (Score:4, Funny)
Re:One time pad (Score:4, Informative)
That is exactly the point of quantum cryptography. The cryptographic key is the one time pad, negotiated between two parties, using superposition (and in some cases entanglement) in order to come to agreement on the pad and at the same time detect evesdroppers.