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Farcasting and Quantum Encryption

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Tue, 2012-11-27 07:12

Lorsa

Farcasting and Quantum Encryption

The core book says the following about Quantum Farcasters:

Quote:
Quantum farcasters are special computers designed to protect a communications channel (such as fiberoptic, radio, laser/microwave, or neutrino) with unbreakable encryption. To function, two or more quantum farcaster computers must first be entangled together (on a quantum level) in the same physical location. The farcasters may then be separated, at which point they may continue to exchange encrypted data via quantum teleportation. This data exchange requires a standard communications link (fiberoptic, radio, laser/microwave, or neutrino), and so is limited by the speed of light, but it is a high bandwidth form of communications. The quantum encryption used by these entangled farcasters is unbreakable, and any attempted interception is immediately detected and neutralized. A quantum farcaster may not be used to securely communicate with any farcasters other than the ones it is entangled with.

Now I have been trying to make sense of this but without success. It says they exchange encrypted data via quantum teleportation yet the transfer requires standard communication. Isn't that contradictory? Moreoever, how come this quantum teleported (or not) data does not use up Qubits? How is it possible to detect any interception? Is it only the key used for encryption that is being transmitted through quantum entaglement and in that case why is the data itself impossible to break? Could someone please enlighten me as to how quantum encrypted farcasting is supposed to work? Also, while on the subject, why is "quantum encryption" (whatever it actually means) only possible for communication and not stored data? Any input on the subject would be welcome.

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Tue, 2012-11-27 15:05

NewtonPulsifer NewtonPulsifer's picture

I'm guessing your confusion

I'm guessing your confusion is probably due to the writer of that blurb using the term quantum teleportation in its meaning as used in real world modern quantum physics. The instantaneous QE (Quantum Entanglement) communication devices in Eclipse Phase are impossible according to currently understood physics. So for this discussion, they simply don't exist. Next, this is a continually evolving field of knowledge, so what I write next could get outdated rather quickly. Basically "real world" quantum teleportation can only "teleport" quantum information, not classical information. So it is useless to transmit most forms of data. However, using quantum states can be usefully used for for securing communications, because the sender and receiver have very precise information on the states of the particles being sent back and forth. This allows them to easily characterize any interference that might arise, including the interference created by a third party attempting to read the state of the particles. This has a side effect of tending to reduce the effect of jamming or interference (its possible to pick out the particles that have quantum states that are still "good/untouched" and the ones that are irretrievably trashed). Many Quantum Key Distribution schemes in prototype now only use quantum state encoding for the exhange of the secret keys, and transmit the rest of the encrypted data in a standard classical manner. Mostly because it's a pain in the butt to get high data rates on the quantum-only channel(s) with current tech/practice. Eclipse Phase technology manages to jam [i]all[/i] the transmission into particles encoded with quantum states. As for using quantum states to encrypt stored data, you absolutely could do that. However, quantum states can be fragile and prone to breaking, so it is only practical if you could figure out a robust means of storing quantum states that won't break down too easily/quickly. It is probably more practical to just use regular symmetric cipher based encryption, or one time pads, for your data/files.

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"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve."- Isoroku Yamamoto

Tue, 2012-11-27 19:21

Jaberwo

Well I thought I understood

Well I thought I understood these things more or less before I read Newtons' comment, but now I'm not sure anymore.. Still, my interpretation of this: In EP you can make quantum entangled bits and then separate them. Then you have two reservoirs of bits that can be consumed to transmit data. This happens instantly and without any radiowaves or something else, over any distance. They are quite expensive and pure magitech. Another thing is quantum farcasting. You can fabricate two communication devices in the same location and then separate them. They can be anything from radio to laser to neutrino based and don't need to be directed. Super secure communication is only possible between the two devices and nothing else, but this communication is unbreakable. Normal sending and receiving seems to work as usual. This has not much to do with real quantum encryption of communication channels. (Afaik) (I think in real quantum encryption (which should rather be called quantum key distribution) a directed beam (e. g. through a fiberoptic cable) is needed, because how do you want to know if someone eavedrops on you from somewhere else than between you and your partner? The photons you send somwhere else than your partner wouldn't come back or be measured no matter if there is an eavsdropper or not. Anyhow, I'm pretty sure real QKD doesn't work on omnidirectional radio, and it doesn't require the communication partners to be in one place at the beginning) A lot more important than these (more or less magic) technologies are symmetric and asymmetric codes and one time pads. Asymmetric encryption is very cool because you don't need to meet physically to exchange the key or find a safe way to do it over a distance. You can read about that in wikipedia. You give away a public key that can be used to encrypt data which only you can decrypt with your private key. Also you can prove that you sent something by encrypting it with your private key, because only your public key will be able to decrypt it. But this can be cracked by quantum computers in a few days or weeks. (these quantum computers have not much to do with quantum key distribution, quantum farcaster or quantum entanglement communication) Symmetric keys are used to encrypt _and_ decrypt a message as opposed to asymmetric keys. But they need to be transfered safely, probably by exchanging physical storage device or a tight laser beam. They can only used between the people who got these keys. They are nearly uncrackable because it takes prohibitively long to do so. If your symmetric key is longer than the text you encrypt you have a one time pad. This is unbreakable, even for TITANs. Symmetric and asymmetric codes and one time pads can be used on communication channels and data alike. Someone correct me if I'm worng.

Tue, 2012-11-27 23:24

The Doctor The Doctor's picture

Jaberwo wrote:In EP you can

Jaberwo wrote:
In EP you can make quantum entangled bits and then separate them. Then you have two reservoirs of bits that can be consumed to transmit data. This happens instantly and without any radiowaves or something else, over any distance. They are quite expensive and pure magitech.

Correct. Not so much magitech as it is what is currently bleeding edge technology moved forward into a time where it's common but still expensive (in several senses of the word).

Jaberwo wrote:
Another thing is quantum farcasting. You can fabricate two communication devices in the same location and then separate them. They can be anything from radio to laser to neutrino based and don't need to be directed. Super secure communication is only possible between the two devices and nothing else, but this communication is unbreakable. Normal sending and receiving seems to work as usual. This has not much to do with real quantum encryption of communication channels. (Afaik)

I would need to reread those bits of the corebook (long day; anyone who wants to correct me on this, feel free to do so), but that sounds like quantum key distribution. Keying material is more or less instantaneously exchanged, plaintext is converted into cyphertext, cyphertext is transmitted, cyphertext is converted back into plaintext with the shared key.

Jaberwo wrote:
(I think in real quantum encryption (which should rather be called quantum key distribution) a directed beam (e. g. through a fiberoptic cable) is needed, because how do you want to know if someone eavedrops on you from somewhere else than between you and your partner?

That is how people have been implementing it in real life so far, yes.

Jaberwo wrote:
The photons you send somwhere else than your partner wouldn't come back or be measured no matter if there is an eavsdropper or not. Anyhow, I'm pretty sure real QKD doesn't work on omnidirectional radio, and it doesn't require the communication partners to be in one place at the beginning)

QKD does not require that Alice and Bob be entangled, no. However, at least one existing quantum key distribution system has been subjected to a successful man in the middle attack in recent memory, so this bit might wind up getting patched in another release of the corebook. :) Here is [url=http://physicsworld.com/cws/article/news/2011/jun/17/hackers-steal-quant... article[/url] and [url=http://arxiv.org/abs/1011.0105]the paper on arXiv[/url].

Jaberwo wrote:
Asymmetric encryption is very cool because you don't need to meet physically to exchange the key or find a safe way to do it over a distance. You can read about that in wikipedia.

It does neatly solve the key distribution problem. At this point, network latency and verification of the keys are bigger problems.

Jaberwo wrote:
But this can be cracked by quantum computers in a few days or weeks. (these quantum computers have not much to do with quantum key distribution, quantum farcaster or quantum entanglement communication)

Sort of. Kind of. Post-quantum cryptography is a hot area of research right now and it is being experimented with; in my games post-quantum cryptosystems are still vulnerable to QC's, but their sophistication accounts for the days-to-weeks required to break the crypto. Cryptosystems which are proof against QC's (and advanced QC research to attack those) is left as potential plot bunnies for enterprising GMs. You are, however, correct in that EP's QC's have nothing to do with key distribution, fasrcasting, or communication. They seem to be for cryptologic purposes only.

Jaberwo wrote:
Symmetric keys are used to encrypt _and_ decrypt a message as opposed to asymmetric keys. But they need to be transfered safely, probably by exchanging physical storage device or a tight laser beam.

Or carried by egocasting couriers, who take the contents of their mesh inserts with them when they unsleeve.

Jaberwo wrote:
They can only used between the people who got these keys. They are nearly uncrackable because it takes prohibitively long to do so.

It depends on the cryptosystem. One time pads are provably uncrackable because the symmetric keys are as long (or longer) than the plaintext. It is when you apply shorter symmetric keys to a plaintext that the probability of cryptologically actionable bits of information being leaked begins to grow.

Jaberwo wrote:
If your symmetric key is longer than the text you encrypt you have a one time pad. This is unbreakable, even for TITANs.

Unless the GM says otherwise.

Jaberwo wrote:
Symmetric and asymmetric codes and one time pads can be used on communication channels and data alike. Someone correct me if I'm worng.

You have a lot of it right. There are, however, bits that you may wish to change to make your game more interesting (to add plot bits).

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Wed, 2012-11-28 05:21

Lorsa

Thanks for all your input!

Thanks for all your input! However it is still not clear to me what is happening. So to NewtonPulsifier: Do you have any links about this that I can read? You mention sending particles back and forth and then reading the states but that seems to me simply as a way to store information. This state means 1 and that means 0 and then you use it for communication but how does that make it secure? I know that real instantanous quantum entanglement communication is impossible but I can still understand it and thus break my suspesion of disbelief enough to assume they made some tech that somehow made it work. The books (and yours) explanation of what happens with quantum encryption is something I still don't understand. Jaberwo: You explain very well what the book says you can do. It doesn't however help me understand what quantum farcasting is, why it needs two communication devices to be "entangled", speak of "quantum teleportation" and then require additional means of transmitting information which then "automatically detects any spying attempts". Somehow this seems even more made up than instantanous QE communication that we know doesn't work but at least have an explanation for. The Doctor: Can't you take your blue box and show up in my living room and explain it to me? :) Jokes aside, you provide some good thoughts on file encryption in general. We did have some discussions as to exactly how safe you could make your own files and if it would be fun or not to have "uncrackable" file encryption. Still, it is the quantum encryption farcasting bit I still really can't wrap my head around. So please re-read those bits and see what you think!

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Wed, 2012-11-28 12:21

NewtonPulsifer NewtonPulsifer's picture

The Doctor wrote:Jaberwo

The Doctor wrote:
Jaberwo wrote:
In EP you can make quantum entangled bits and then separate them. Then you have two reservoirs of bits that can be consumed to transmit data. This happens instantly and without any radiowaves or something else, over any distance. They are quite expensive and pure magitech.
Correct. Not so much magitech as it is what is currently bleeding edge technology moved forward into a time where it's common but still expensive (in several senses of the word).

Has FTL communication been demonstrated even in a proposed thought experiment? I think that would have been big news. In the absence of news, I agree with magitech as an apt description.

TheDoctor wrote:
Jaberwo wrote:
Another thing is quantum farcasting. You can fabricate two communication devices in the same location and then separate them. They can be anything from radio to laser to neutrino based and don't need to be directed. Super secure communication is only possible between the two devices and nothing else, but this communication is unbreakable. Normal sending and receiving seems to work as usual. This has not much to do with real quantum encryption of communication channels. (Afaik)
I would need to reread those bits of the corebook (long day; anyone who wants to correct me on this, feel free to do so), but that sounds like quantum key distribution. Keying material is more or less instantaneously exchanged, plaintext is converted into cyphertext, cyphertext is transmitted, cyphertext is converted back into plaintext with the shared key.

Yes, that description where they need to be physical co-located seems rather silly, right? Couldn't you just swap oldskool symmetric keys or a huge quantity of one-time pads at that point? Where does quantum key distribution become necessary [i]at all[/i] at that point?

TheDoctor wrote:
Jaberwo wrote:
(I think in real quantum encryption (which should rather be called quantum key distribution) a directed beam (e. g. through a fiberoptic cable) is needed, because how do you want to know if someone eavedrops on you from somewhere else than between you and your partner?
That is how people have been implementing it in real life so far, yes.

A secure quantum communication system has to assume someone is tapping the line - because they could be. A big problem with broadcast quantum communication is that it would violate a well established theorem in quantum physics. However there's nothing stopping you from using multiple different optical cavities (essentially its possibly thousands/gazillions of communicators all rolled into one, pointing their different directions) nor a sweeping search pattern that I'm aware of to have two quantum communicators try to "find" each other. The chance of this working rapidly or at all gets very unlikely the farther apart you are, though. So most likely two quantum radios are going to use classical communications broadcasts to locate each other, and then switch to tight/laser beam. In addition, communication between randomly moving communicators is going to be a problem. Realistically you'd want to rely on quantum communication routers that are at fixed known locations to get your message to/from its destination if you don't know each other's precise location. Re: optical cables you can also use "switches" to get your photons directly between communicators in a public fibre network (assuming that network is equipped to handle this), so you don't need a dedicated end-to-end cable.

TheDoctor wrote:
Jaberwo wrote:
The photons you send somwhere else than your partner wouldn't come back or be measured no matter if there is an eavsdropper or not. Anyhow, I'm pretty sure real QKD doesn't work on omnidirectional radio, and it doesn't require the communication partners to be in one place at the beginning)
QKD does not require that Alice and Bob be entangled, no. However, at least one existing quantum key distribution system has been subjected to a successful man in the middle attack in recent memory, so this bit might wind up getting patched in another release of the corebook. :) Here is [url=http://physicsworld.com/cws/article/news/2011/jun/17/hackers-steal-quant... article[/url] and [url=http://arxiv.org/abs/1011.0105]the paper on arXiv[/url].

There's recent research that it is not necessary to send any actual particles on the quantum channel at all. Just the quantum channel existing alone is enough (paper here). Whether this scheme succumbs to a clever exploit in a few months or years remains to be seen.

TheDoctor wrote:
Jaberwo wrote:
Symmetric keys are used to encrypt _and_ decrypt a message as opposed to asymmetric keys. But they need to be transfered safely, probably by exchanging physical storage device or a tight laser beam.
Or carried by egocasting couriers, who take the contents of their mesh inserts with them when they unsleeve.

If you trust the security practices of the receiving egocaster, and you're sending your ego over on a secure channel to them....you already have a secure trusted channel. Courier seems unnecessary at that point, unless you're wanting to do a surprise audit of their infosec practices.

TheDoctor wrote:
Jaberwo wrote:
They can only used between the people who got these keys. They are nearly uncrackable because it takes prohibitively long to do so.
It depends on the cryptosystem. One time pads are provably uncrackable because the symmetric keys are as long (or longer) than the plaintext. It is when you apply shorter symmetric keys to a plaintext that the probability of cryptologically actionable bits of information being leaked begins to grow.

With the speed of EP tech, I think we can be sure that the symmetric keys can be of paranoid-satisfyingly long length. To paraphrase Bruce Schneier, there's two levels of cryptography - the kind that keeps out your kid sister, and the kind that keeps out major governments. In EP, anything sold/implemented post-TITAN is going to be of the latter. I think the culture of info security in EP is going to be much much different than it is nowadays because everybody knows the stakes are way higher in EP.

—

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Wed, 2012-11-28 12:30

NewtonPulsifer NewtonPulsifer's picture

Lorsa wrote:Thanks for all

Lorsa wrote:
Thanks for all your input! However it is still not clear to me what is happening. So to NewtonPulsifier: Do you have any links about this that I can read? You mention sending particles back and forth and then reading the states but that seems to me simply as a way to store information. This state means 1 and that means 0 and then you use it for communication but how does that make it secure? I know that real instantanous quantum entanglement communication is impossible but I can still understand it and thus break my suspesion of disbelief enough to assume they made some tech that somehow made it work. The books (and yours) explanation of what happens with quantum encryption is something I still don't understand.

It's just not that easy to break it down into a soundbite, sorry. Quantum physics isn't intuitive, so there's no great analogy that one can come up with to create a quick rough understanding of it. The Wikipedia article isn't terrible: https://en.wikipedia.org/wiki/Quantum_encryption Here's some links to show how weird quantum stuff can be: http://scienceblogs.com/principles/2012/05/04/entangled-in-the-past-expe... https://en.wikipedia.org/wiki/Quantum_Zeno_effect http://www.newscientist.com/article/dn21235-entangled-diamonds-blur-quan... https://en.wikipedia.org/wiki/Elitzur%E2%80%93Vaidman_bomb_tester

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Thu, 2012-11-29 08:03

Lorsa

NewtonPulsifer wrote:It's

NewtonPulsifer wrote:
It's just not that easy to break it down into a soundbite, sorry. Quantum physics isn't intuitive, so there's no great analogy that one can come up with to create a quick rough understanding of it. The Wikipedia article isn't terrible: https://en.wikipedia.org/wiki/Quantum_encryption

I have no problem to understand quantum mechanics, and your explanations can be how mathematical or physical you want. The problem is that the text in the rulebook was so vague and slightly contradictory that with an understanding of quantum mechanics it made little sense. Reading through that wiki page however help a bit. If I understood it right they use quantum state measurment only as a basis for generating a random key. It seems however that this type of communication needs double-information to travel between the two people, first information then comparison of random measurment. I assume this means additional time-lag on all such communications.

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