quantum cryptography

[INIT_6]

I have been reading different reports the last couple months about quantum cryptography and cryptography. Not sure if any of you have looked into this yet or not. I think this is some crazy shit. If any of you know anything about quantum states like entanglement. You will love the report.

Speed boost helps quantum codes on their way

and

Quantum Physics, abstract
quant-ph/0608110

If this gets to a point where it can be used in a real world situation it might stop hackers/crackers for a while.

[BonzoESC]

Re: quantum cryptography

Even now it's hard to break a good cipher. When quantum crypto rolls around, social engineering will still be the best attack.

[Voltage Spike]

Re: quantum cryptography

Even now it's hard to break a good cipher. When quantum crypto rolls around, social engineering will still be the best attack.

The main promise of quantum crypotgraphy isn't that it is going to be really, really, ridiculously hard but that the system can detect all eavesdropping. It doesn't solve the problem of identification (although the current requirement for dedicated lines certainly helps). In short, it is a significant step toward preventing "line taps" by unauthorized persons.

[bascule]

Re: quantum cryptography

The main promise of quantum crypotgraphy isn't that it is going to be really, really, ridiculously hard but that the system can detect all eavesdropping.

Quantum encryption is heavily misunderstood.

The "detect eavesdropping" part you're discussing has to do with streaming dissemination of the pad.

The underlying encryption process is that of a one time pad, which results in mathematically provable "perfect secrecy", i.e. the statistical properties of the ciphertext are at least as random as the pad) Thus the important part in the security of OTP becomes the statistical properties of the pad. Anything but a perfectly random pad compromises the statistical properties of the ciphertext and thus provides a potential attack vector.

Following two seminal discoveries in quantum physics, the uncertainty principle and entanglement, a debate began to rage as to whether the seemingly random nature of waveform collapse was, in fact, random after all. A debate began to rage as to whether waveform collapse was truly non-deterministic or whether it could be the result of as-yet-undiscovered hidden variables.

In 1964, a physicist named John Bell continued work Einstein had done on entanglement (the so-called EPR paradox) and created Bell's Inequality, which should hold true in the event that quantum indeterminacy is the result of local hidden variables. In 1972, Bell's inequality was violated experimentally. Subsequent experiments have violated Bell's inequality as well. This means that non-local hidden variables are not responsible for quantum indeterminacy because the distribution of any measured quantum property for two entangled particles is statistically random.

When you collapse the waveform of an entangled particle, it collapses the waveform of the particle it's entangled with as well. The two particles collapse in the same manner, so that if you measure the spin of the entangled particles when their waveform collapse, it will be the same. And, as the violation of Bell's equality has experimentally shown, the pattern exhibited by any measured property, while the same for both entangled particles, exhibits a random distribution.

Entangled particles provide an excellent channel for transmitting a OTP to two remote destinations. This is because, in effect, the pad does not EXIST until one end has collapsed the wavefunction, thanks to quantum superposition.

Compare this, to, say, some sort of random number generator linked to two remote sites via a fiber optic cable. One could easily compromise the pad by splicing into the fiber optic cable and reading the pattern of photons being transmitted from the random number generator. Thus with this approach, it's possible to compromise the transmission of the pad through eavesdropping. Thus for purposes of telecommunication, you must ensure the physical security of the fiber optic line for its entire length if you wish to ensure the secrecy of the pad.

Quantum cryptography, rather than sending pulses of photons to two remote locations, sends a nonstop stream of entangled particles to two destinations. Great care must be taken to ensure that the particles remain entangled throughout their trip through the fiber optic line. Any attempt to splice into the fiber optic line will collapse the entangled particles on the other end, long before their quantum properties can be measured. Thus the only place you need worry about the pad being compromised is at either of the receiving stations (of course, someone could always cut the fiber optic line to disrupt the pad)

Once you have the pad, you still need some other mechanism of transmitting the ciphertext. However, you don't have to worry about anyone evesdropping on the ciphertext. Without the pad, the ciphertext is completely worthless, since OTP provides perfect secrecy.

[Voltage Spike]

Re: quantum cryptography

Quantum encryption is heavily misunderstood.

Thanks for the clarification. I suppose that the ability to prevent eavesdropping combined with a source of true randomness (which I didn't know about) is a good recipe for implementing one-time pads. It's certainly not a complete solution to all of the world's cryptography needs, then, but it sure does help in some areas.

Out of curiosity, is it possible to simultaneously send entangled particles (for the keystream) and traditional photon streams (for the message) within the same fiber optic line?

[BonzoESC]

Re: quantum cryptography

Thanks for the clarification. I suppose that the ability to prevent eavesdropping combined with a source of true randomness (which I didn't know about) is a good recipe for implementing one-time pads. It's certainly not a complete solution to all of the world's cryptography needs, then, but it sure does help in some areas.

Out of curiosity, is it possible to simultaneously send entangled particles (for the keystream) and traditional photon streams (for the message) within the same fiber optic line?

You could also put a copy of your OTP in the same envelope as the ciphertext.

[Voltage Spike]

Re: quantum cryptography

You could also put a copy of your OTP in the same envelope as the ciphertext.

I'm still not sure I entirely understand the concept (one post in a public forum certainly isn't going to make me an expert), but, from my understanding of bascule's post, your suggestion doesn't make sense. The pad isn't data in the classical sense that can be dropped into a message stream but rather data inferred from quantum states which aren't directly under control of the sender.

Unless you are implying that the ciphertext can be sent using entangled particles that can be observed twice: once for their quantum state and then again for their message. That would, however, violate my understanding of quantum entanglement ... not that my understanding is worth much.

[INIT_6]

Re: quantum cryptography

I only understand the main idea be hide this quantum cryptography.

They say that consciousness can effect things at the quantum physical layer. Now if this is indeed true would this effect the quantum cryptography. Meaning could just one thought change when the collapse the waveform of an entangled particle took place. To collapse the waveform you have to observe it. Could you observe it by a thought?

[BonzoESC]

Re: quantum cryptography

I only understand the main idea be hide this quantum cryptography.

They say that consciousness can effect things at the quantum physical layer. Now if this is indeed true would this effect the quantum cryptography. Meaning could just one thought change when the collapse the waveform of an entangled particle took place. To collapse the waveform you have to observe it. Could you observe it by a thought?

Consciousness is just an emergent property of some complicated chemical reactions. It's not special or even relevant on a quantum level. The whole fantasy that thoughts can affect quantum events directly without fancy and expensive tools is preposterous and a wishful attempt to read mysticality and other new age pseudoscience BS into a science that cannot suggest even a link with it. http://en.wikipedia.org/wiki/Quantum_mind#Criticisms has some more criticism of the matter, but basically you can't just say something like "consciousness can affect things at the quantum physical layer," without an actual scientific experiment to back it up.

Observing in the quantum sense is basically a destructive process by which something is bounced off a particle to determine its state, while at the same time that event changes its state in an unpredictable way.

That inability to "observe" the particle nondestructively leads to Heisenberg's Uncertainty Principle.

[INIT_6]

Re: quantum cryptography

I am sorry if I have mis-lead you. I know that the whole idea of Consciousness effecting something out side of it's self. doesn't sound like it would work.

Most of what I know about the quantum world is from two places. One is the movie "what the bleep do we know" and for the other side, Newscientist.com.

I will change my question. If consciousness could effect the quantum world would this make the quantum cryptography not work? I would think yes.

I don't like to belive in any one thing. I like to try to understand all point of views.

I know I am no expert at any of this. I just read few articles here and there. in hopes I can sound as cool as you guys, even thou I have much to learn before I reach your guys status.

bascule seems to have a great knoweldge of what is going on. I respect/think he is true with what he said above. Even thou I could only understand half of it :)

[TheCotMan]

Re: quantum cryptography

Look back through the video archives. There was a pretty good presentation on QuantumCrypto provided by a professor at some University in Texas (if I recall correctly) at, um... Defcon 12?

There was also a poorly prepared and poorly presented one at Defcon 10? (All this stuff is running together.) The "Bad" presentation was so bad, that I got up and walked out-- and that is something I seldom do to a speaker.

*Bad: Speaker was stumbling over their own words, having problems remember what step was next. After enough floundering, people in the audience started yelling out answers to "what was next" and the words the speaker was looking for.

Perhaps he was just nervous? [Maybe he had been partying in Decon style the night before??] I don't know, but I was unimpressed.

The one provided by the professor (from Texas) was a good introduction to quantum Crypto, in my opinion.

If you look for and find these videos, link to them so other people finding this thread, also find the videos. :-)

[INIT_6]

Re: quantum cryptography

The defcon 10 guy:
Richard Thieme Is the one from Defcon 12

Resources

realVideo

realAudio

[BonzoESC]

Re: quantum cryptography

Most of what I know about the quantum world is from two places. One is the movie "what the bleep do we know"

Ignore those new-age feel-good hippy pseudoscience liars. Honestly I'm not sure which movie represents a greater travesty against physics: that movie or "Transporter 2."

To clarify: you might want to get your scientific information from sources that don't base all their facts on a "medium" who claims to be a reincarnated atlantean warrior.

[bascule]

Re: quantum cryptography

Out of curiosity, is it possible to simultaneously send entangled particles (for the keystream) and traditional photon streams (for the message) within the same fiber optic line?

I don't know enough about the practical implementation of quantum crypto to know if that's possible. If nothing else, you could run two cables. I could talk out my ass and say that it's possible with something like polarization, but talking out your ass is bad.

Ignore those new-age feel-good hippy pseudoscience liars.

Yes, don't bother with any "information" you got from that film. Its aim is to confuddle the physics knowledge of the public.

They introduce a lot of the quantum mind crap argued for by the physicist Sir Roger Penrose, author of such books as The Road to Reality (which is an awesome and incredibly comprehensive physics book, by the way)

Penrose is thoroughly convinced that mind is non-deterministic and will never be explained by science. He's written three books on the subject, attempting such things as mathematical proofs that consciousness is non-computable.

His mathematical proofs have been trashed by fellow mathematicians. His biological and quantum hypotheses have been thoroughly rejected by both biologists and quantum physicists.

Bottom line: the stastical distribution produced by wafeorm collapse in regard to properties like spin has been shown to be random in every experiment performed to date. Only a non-local theory of waveform collapse will allow us to decipher the mechanisms behind the source of the distribution. Until then, it is, for all intents and purposes, non-deterministic.

[VAX_to_PBX]

Re: quantum cryptography

First off congrats to Bascule for making one of the best posts I've seen in a long time.

Now to the subject at hand.

My knowledge on quantum crypto goes as far as the generalized presentation's hosted by Los Alamos researchers. Which is over generalized for public reading.

I just wanted to comment on the one reply mentioning the knowledge of the Human Mind.

I remember an excerpt from Norbert Wieners' book on Cybernetics, and the relevance between man, and animal. It basiclly stated the biological membrane in human, and animal can be seen as highly copressed boolean clusters on a fixed node neural network. The node count evolves with evolution of course, but the point is clear.

ai.mit.edu has a neat article where they compare the human minds' complexity with the MIPS of every computer in the world connected on short trunk optical networks. Needless to say the mind won over, but the likelyhood of the human mind being put into a reference model based on any level of our current scientific assumptions is very unlikely.

This reminds me of the "morons" in college who use to claim the scientific community assumed they knew what they where talking about because they could make consumer electronics for practical uses. Who's to say our entire perspective on energy, and numbers is correct because we can make cell phones, and make what we think are efficient calculation's on such thing's as optics, and probability?

It's pretty obvious I'm just "little people," but architecture and system's still interests' me!