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Encryption Security

Securing Fiber Using Light Polarization 152

Posted by timothy from the gentlemen-sharpen-your-flashlights dept.
screenbert writes: "A new and novel way of communicating over fiber optics is being developed by physicists supported by the Office of Naval Research. Rather than using the amplitude and frequency of electromagnetic waves, they're using the polarization of the wave to carry the signal. Such a method offers a novel and elegant method of secure communication over fiber optic lines. This press release has more information. Of course I always thought that fiber was always pretty secure anyway since it's a lot harder to tap than copper."
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Securing Fiber Using Light Polarization More

Securing Fiber Using Light Polarization

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  • More Secure... (Score:3, Insightful)

    by jgdobak ( 119142 ) on Monday August 19, 2002 @02:55PM (#4099830)
    ...until polarizaton-based recievers become widespread, anyway.

    Security through exclusivity ("It'll be secure, because we're the ONLY PEOPLE who have the hardware to read it!") doesn't work for very long.

    Not that it's easy to tap fibers, anyway... Even if you have the equipment, you have to figure out which fiber out of 288 or more is the one you need, and the documentation is usually kept locked up tight.
    • How long do you guys think it is before we have fiber everywhere? I'm pretty sure that Internet2 is gonna be fiber, but that's only for Universities and major corporations, right?
      • "How long do you guys think it is before we have fiber everywhere?"

        Forever. Wireless is a much cheaper last mile solution. Hell, we don't have CABLE everywhere.

        "I'm pretty sure that Internet2 is gonna be fiber, but that's only for Universities and major corporations, right?"
        I'm pretty sure Internet2 already exists and has nothing to do with fiber or not.

        Engage brain before posting.

      • Re:More Secure... (Score:3, Informative)

        by jgdobak ( 119142 )
        There's alot more fiber out there than you may think. Any cable TV system newer than 1995 or so consists of more fiber than copper by the distance the signal travels.

        Very new systems are quite literally fiber to the curb.

        Were it not for the expense involved in termination (and the precision required), fiber into the home would be feasible.
        • If you are a large instution like, say, a university, the cable feed you get is fibre. At the U of A we have a fibre feed from the cable company that then gets converted to copper, split up and fed to a bank of channel reclockers (so we can change the channel mappings) and MPEG-2 decoders for things like Fox Sports, then re-joined and sent to the dorms as copper.

    • Re:More Secure... (Score:4, Informative)

      by Jobe_br ( 27348 ) <bdruth.gmail@com> on Monday August 19, 2002 @03:02PM (#4099889)
      This article (did you read it?) doesn't have anything to do with security through exclusivity. The "signal" is encoded in the chaotic "noise" that occurs in a light "circle" and that noise is subtracted from the total received communication at the receiving end to come up with the "signal" again. The researchers have come up with what I would call a type of quantum interference encryption using light (instead of quantum particles). The encryption exists in the chaos of the system rendering the signal received by an eaves dropper useless.

      • Re:More Secure... (Score:2, Insightful)

        by jgdobak ( 119142 )
        My point was that since the "encryption" comes along with the "signal", all you have to do is hook a "polarization-based" reciever to it to listen... No special token required.

        Hence, it'll be secure until anyone with the right dosh can get their hands on one of these recievers.

        • Re:More Secure... (Score:2, Interesting)

          by Luk Fugl ( 586096 )

          it'll be secure until anyone with the right
          dosh can get their hands on one of these
          recievers

          Not quite, compare the Enigma encryption machine from WWII. The machine wasn't the encryption, just the device (although the machine itself was quite clever). Without knowing the proper setting for the machine, it was near worthless. The allies had their hands on Enigma for several years before they came up with a cryptanalytic method (kudos to the Poles!) that made the physical machine they had worth something. The encryption is in the signal and noise, not in the machine that reads it.
          • "The allies had their hands on Enigma for several years before they came up with a cryptanalytic method (kudos to the Poles!)..."

            Must...resist...politically incorrect joke........about polish people... and how many it takes.... to say something nobody understands.... argh!

    • Re:More Secure... (Score:1, Interesting)

      by russotto ( 537200 )
      Quite likely nobody knows which fiber is the one you need. As I understand it, after a break and splice, the fibers may be scrambled -- so the receivers on either end go through a discovery process to figure out how things are hooked up now.

      However, tapping a fiber isn't that difficult in principle -- you bend it just enough so some light escapes.

    • Re:More Secure... (Score:1, Interesting)

      by uberdave ( 526529 )
      Even if you have the equipment, you have to figure out which fiber out of 288 or more is the one you need, and the documentation is usually kept locked up tight.

      Which is just security through exclusivity/obscurity, right?
      • Yeah, until someone gets their hands on the documentation and duplicates it. The point is to make sure the key isn't copied, if you will.

        This method of transmission seems pretty much the same... Eavesdroppers can't listen until they get one of these nifty new recievers that can interpret it.
      • Which is just security through exclusivity/obscurity, right?
        Yes. Security through obscurity is necessary, but not complete. It sure does help a whole lot, but you shouldn't rely upon it. If you think security through obscurity is useless, please forward your bank account numbers and PIN to me. Thank you.
      • This is exactly why confidential information such as this should be kept on a laptop computer. The chance of our government losing a laptop computer is almost non-existent!

    • Re:More Secure... (Score:2, Informative)

      by jordanda ( 160179 )
      That is not the basis of the scheme at all. You cannot the polarization of a wave of light with out changing it. It's one of those uncertainty principle things. The idea behind this scheme is not security through obscurity. It actually takes advantage of the properties of light to be sure that the signal can only be tapped by once. If the message that comes out on the other side is not all fucked up then they know that the the message was not comprimised.
      • Oh? My bad, then.

        You learn something new every day.
      • Damn. I need to read my posts before I click submit. My previous post is completely incomprehensable.

        I'll start over.... The security scheme at work here is not "no one has the hardware to read this signal therefore it's secure." It is actually impossible to test the polarization of a wave without changeing that polarization (a la uncertainty principle). If a third party tries to tap the signal they will inevitably end up changing that signal in a detectable way. The communicating parties will quickly discover they are being tapped and can stop broadcasting immediatly.

        • It's easy to tell a fiber signal is being tapped as transmission equipment is.

          Light is finite. If some power is diverted to an eavesdropping reciever, the amount the intended receiver will recieve will drop proportionately.

          Most optical recievers are intelligent enough to set off an alarm if light drops significantly during operation, even if the drop doesn't make the signal untenable.

          Any eavesdropping has to be very professional or very quickly done, or the eavesdropped have to be very incompetant, for it to not be noticed.
          • Someone else linked to this article [com.com] about the NSA tapping fiber. In it, they talked to the people who lay fiber, and they say it's not unheard of for a fishing ship to drop ancor at exactly the wrong spot and cut the line.

            So, the question now is how many of those accidents were really accidents? A fishing ship inadvertently cuts the line, a sub a few thousand miles further down splices into the fiber before they can fix it. The fiber's offline anyway, so no one notices. When they come back online, they'll notice some slight signal degradation, but they'll blame it on their own repair job.
          • Considering that they'd need to put a splice in at the exact point of the break, and there's a tap in place there, they'd probably notice it...
        • The communicating parties will quickly discover they are being tapped and can stop broadcasting immediatly.

          Actually, they only know there is a problem. It could be the NIC's the software, or anything like that. So although I agree with you, I think that detection would only come through basic troubleshooting.
      • You cannot [measure] the polarization of a wave of light with out changing it.

        Thats the theory behind quantum encryption, in which single photons are used to create a shared key by playing tricks with polarisation. The important point is the words "single photon".

        However QE cannot work over long distances because photons get lost (i.e. attenuation). General purpose signalling sends a lot of photons so that at least a few get through (I think the detection level for general purpose detectors without special cooling is around 70 photons). They also get amplified. I'm not sure if fibre amplifiers maintain polarisation. If not then this technique is just an interesting novelty.

        So tapping would be easy. Just put the signal through a splitter (e.g. a bend in the fibre) and route your half of the signal to a decoder that works in the same way as the official one. The other end sees a 3dB drop in signal, but thats probably too small to be noticed.

        Where this might be important is increased bandwidth. At the moment fibre transmission uses binary keying: send photons for 1, no photons for 0. Polarisation modulation means that you could use several different angles, and hence encode more than one bit per light pulse.

        But don't get too excited about the bandwidth either. The limiting factor on bandwidth at the moment is the routers at the end of the fibre. We can pump terabits down a fibre in the lab, and 100 Gbit is pretty straighforward to do in the field. But put ten 100Gbit links into a router and you have to have a machine that can switch 1 Tbit. If the average packet is 1.5kbytes (Ethernet frame) then thats around 83 million packets per second. Even with hardware assist thats an awful lot of address table lookups per second.

        Paul.

  • So taking a photo with your instant camera and sending it down the line is faster than using light? That's one helluva trick!

  • Somebody explain (Score:3, Insightful)

    by scott1853 ( 194884 ) on Monday August 19, 2002 @02:59PM (#4099865)
    How do you secure a physical medium from interception? If you intercept a signal, can't you just rebroadcast the same signal back out as long as it was read correctly in the first place? Isn't the real security in the encryption of the data being transmitted over the medium?
    • Only if the eavesdropper knows exactly which strand to 'listen in on'. And has the hardware to do so...

    • Not really. A light polarization can't be so easilly reproduced, as intensity can.
      • finally someone has an open mind on the subject. "not so easily" is much easier to swallow than "can't". Maybe i "can't" reproduce light polarization today, but are you telling me I will never ever figure out how to pull it off? It's inevitable that every "can't" will one day be engineered into a "can". A statement like, "You can't detect a light polarization without changing it is a hefty generalization, I'll bet you can even if you have to reproduce/repeat the polarization process to make the outgoing signal seem untampered with...
        • No, actually they mean can't. It's not like saying "All the kings horses and all the king's men couldn't put humpty dumpty back together again", it's like saying "you can't destroy matter without creating energy." When a physicist says "can't," he means "can't," not "probably won't"
    • This method is secure because you cannot intercept the signal and still. With standard light techniques it is possible to place yourself as the "man in the middle", intercept the stream of light and re-broadcast it though the fiber. Using polarization as the encoding technique this is not possible because the system can be designed so that you cannot guess exactly what is the exact polarization of the bit you just received, and so you cannot re-broadcast it adequately.

      Simon Singh in its book "The Code Boob" has a interesting explanation of one such system; it is tool lengthy to quote here (and I don't have the book with me now) but I highly recommend reading it.
      • Too fast on the "submit" button for my own good ...

        On the first paragraph, read "intercept the signal and still be able to re-broadcast it un-corrupted".

        On the second paragraph, the correct name is "The Code Book" [amazon.com], as you all probably know.
      • Why do you need to guess the exact polarization of the bit you just received? Why can't you just detect it?

        And if resolution of your detector won't give you the EXACT polarizarion, how come you can't just make one that's as least as good as the detector, then they won't be able to tell the difference either...

    • Re:Somebody explain (Score:2, Insightful)

      by evalhalla ( 581819 )

      To reproduce a light polarization you have to modify it, so the one who receives the signal knows that it has been intercepted.

      Of course if you're sending unencrypted sensible informations you only know that something bad happened (which is only slightly better than something bad happening without you knowing), but if you're sending data such as the key for an encryption system you can decide whether to use it or not basing on the fact that you're sure whether it has been intercepted or not.

      • To reproduce a light polarization you have to modify it, so the one who receives the signal knows that it has been intercepted.

        Why can't you just use a beamsplitter?

        • That would change the polarization.

          • Only for the photons that are observed though, correct? I assume there's some redundancy going on since the receiver isn't going to be able to read every single photon individually.

            Not to mention the man-in-the-middle attack, where the message is simply decrypted and then resent. Without a securely distributed key, you're always going to be vulnerable to that.

            Anyway, it's probably not as simple as just putting in a beamsplitter, but the article wasn't clear enough to me to understand why. I guess I'll look up quantum encryption when I have some time.

            • At least YOU'VE got a clue (Score:1, Informative)

              by Anonymous Coward
              A roundabout way of agreeing with you:

              A polarizing beam splitter projects any incoming light into either of its two orthogonal states of polarization. In quantum-speak, the state of any incoming photon is thrown into an eigenstate of the observing beam splitter.

              However, if many, many photons are passing by, a $200 fused-fiber optical tap (say, from JDSU) we can tap some of them and measure them without throwing the rest into our favorite eigenstates.

              Now many people here are spewing absolute bullshit when they say that it's impossible to reproduce a state of polarization. Stimulated emission does just that.

              What's impossible is to reproduce the state of polarization of a single photon after it's been measured. There is nothing about single photons in the press release.

            • The receiver is able to read every single photon, with a certain probability to read the correct value or not. Then there are ways to tell whether you received the correct photon or not, without actually resending them.

              Again it is a matter of what is being sent: for a one time key you can just send losts of photons, and then keep only the ones that have been received correctly (and without being intercepted!)

              And yes, a good book on quantum encryption could explain this much better than I can do with vague memories from an uni course for which I haven't tried the exam yet. :)

    • Polarization cannot be reproduced. If you pick the wrong polarization (/ instead of |, etc), there's a 50% chance that the polarization will flip. Unless you know the correct polarization sequence, then its impossible to intercept the data.

      As I stated before, this has been around for a long time, and is a foundation of quantum cryptography.

  • It depends. (Score:2, Informative)

    by miffo.swe ( 547642 )
    "Of course I always thought that Fiber was always pretty secure anyway since it's a lot harder to tap than copper."

    Its really not that hard if you want to. The average script kid might not have the money but for corporate espionage its no problem. Just get a fiber capable router or switch. A quick glitch in the transmission and youre in.
  • Help me out here. Polarization modulation is nothing new, right? The trick here is cancelling out the chaotic variations by sending the signal twice and doing the comparison?

    I'm asking because the first sentence of the press release makes it sound like these guys invented polarization modulation, and I'm pretty sure I read about that a looooong time ago.

    • Not just polarization modulation. (Score:4, Informative)

      by mbkennel ( 97636 ) on Monday August 19, 2002 @03:19PM (#4100023)
      The central issue is that in most of the inexpensive single mode fibers, there are random rotations of the polarization state as you transmit light down the fiber.

      Moreover those random shifts are time-dependent on account of the physical fluctuations in environment of the fiber optic channel.

      That makes traditional polarization modulation difficult to do since the receiver has to dynamically track the unknown polarization matrix correpsonding to the transformation, and that is not easy or inexpensive.

      This new method obviates the issue by doing polarization modulation in a distinctly new way, wherein the modulation is in the feedback arm of a chaotic erbium doped fiber ring laser. Changes in the modulation (i.e. message being transmitted) is thus fed back into the dynamics of the transmitter somewhat akin to the state of a cypher (though these schemes are not designed or analyzed to resist cryptanalytic attacks)

      There are a few things combined as one then: the production of light in high power (EDRFL), chaotic signal masking by transmitting a high dimensional chaotic state, modulation based on dynamical polarization differences. Also, detection methods for polarization usually require "coherent detection" i.e. interferometry with a coherent source (local laser)---those detectors are much more expensive and difficult than amplitude detectors that measure the short term intensity. Greg has previously shown a technique to use the ampltitude only detectors to nevertheless extract the instantaneous (and not time averaged) polarization state on the Poincare sphere so I expect such techniques to be used in this paper as well.

      Just polarization differences via time-delay doesn't work either if you don't have a chaotic underlying carrier as too many things cancel.

      I previously collaborated with the two of them on chaotic communication in fiber ring lasers; we derived simulations of the equations of motion and amplitude modulation in the chaotic state. They published experimental results on amplitude modulation in a similar setup before.

  • pr0n! (Score:4, Funny)

    by Renraku ( 518261 ) on Monday August 19, 2002 @03:04PM (#4099905) Homepage
    "It provides a definite advantage over direct encoding of polarization, leaving an eavesdropper only chaotic static, and no means to extract the signal."

    Why the extra security? There's already the depths of the ocean, the difficulty of trying to tap a fiber line, not to mention whatever encryptation they have on their data. They must be looking at some questionable pr0n to go to these lengths.
    • You know, like blueprints on missiles, corporate finances, medical records and such. There are circumstances where the data must not be interceptable by anyone. Not even the US marine thats been sniffing copper for as long as theres been phone lines. I dont think we will see these things in other than military installations and other places where the data is sensitive.

    • The depths of an ocean isn't really a hinderance to a major world power who really wants to know what's being said on a cable. Search 'IVY BELLS' for the details of one of these programs.

  • Quantum Encryption (Score:2, Interesting)

    by FalconRed ( 91401 )
    This method is neither new or novel, it's called Quantum Encruption. You can read a quick primer Here [discover.com]. By using polarized photos, you can trasmit bits that will be impossible to intercept without being detected. Research labs have been working on relaible, long-distance implementation for years.
    • This method is neither new or novel, it's called Quantum Encruption. You can read a quick primer ....

      This ain't quantum encryption. It's much lamer. Read the article. The lame claim is only that the signal is hader to detect, because it's sent at a low level and hidden in noise. Not only is this a bad way to "secure" communications, but bragging that that is what you are doing defeats the whole concept!

    • Encruption - What George W says about security.

      "If the evil doers can use Encruption whom's to say we can't not interseptualize it?"
    • This method is neither new or novel, it's called Quantum Encruption.[sic]

      Well, er, not exactly.

      The technique described in the press release describes a technique for hiding a polarization modulation signal in the polarization state noise inherent in the ring laser system the experimenters used. It's clever, but it's very much not quantum encryption. In principle, it would be possible to siphon a few photons off the fiber and squeeze information out of them, though it would be very difficult. Quantum encryption, as described in the article referenced in the parent post, is a very different technique. It relies on measurements of the polarization states of single photons, not continuous beams. It is immune to (undetected) interception, because tapping the beam irretrievably loses some data (hooray for quantum mechanics.) It is not well-suited to fibre systems--it's difficult to push single photons down a fibre and reliably measure and retain their polarization. It would excel, however, for communcations that could take place over line-of-sight spans, even very long ones.

    • Re: ! Quantum Encryption (Score:1, Interesting)

      by Anonymous Coward
      This is not. This is merely using a polarity of the lambda and a timing seed. The reason it's "secure" is because you would have to have the hardware and the timing key to strip out the intelligence. Right now you would have to put a filter in front of the beam to do this. For the time being, it would be readily obvious if the FO were tampered with by the signal loss. On the other hand, if you know the capacitive and inductive reactants of your phone line you could tell if someone was tapping it between you and the SAC box. So now they wire tap at the CO or before the SAC box at least. I don't think it would take too much work to come up with a way to read the intelligence in a non-intrusive way. Not so long ago plane Jane FO was thought to be secure for the same reason. Now there are OTDR's that can read the signal through the cladding. This rises a question, I wonder how they plan on using repeaters for signal regeneration? What IS cool about this, is the fact you could use this to cram even more intelligence on a single lambda in much the same way QAM allows for higher data rates with a more efficient use of frequency. I know that Bell Labs played with this while working on their optical routers. But hey they did bring us QAM and FO. Now if only they could use that brain power to figure out a way to make a profit! I see a lot of post tossing around the "Quantum Entanglement" phrase. This is not Quantum entanglement. ( NOTE this is a gross over simplification but it makes the point with out the math) In a nutshell Quantum entanglement works like this: Quantum entanglement is when two particles become Quantumly entangled or one particle is split in a way that produces two Quantumly entangled partials. The particles will have an inverse relationship or an "inverse spin". Imagine one spins left the other right. If I keep the left spinning particle and watch it while I transport the right spinning particle to where I want to communicate with. I can effect change on the right spinning partial by affecting my left spinning particle.. Like wise if someone were to "intercept" the right spinning partial I could watch my left spinning particle be affected by the right spinning particle. In this way I could have a clue my data had been tampered with or read. The Problem with this is that to the best of my knowledge no one have ever managed to keep Quantum entanglement for more the short distances. Then math says we should be able to but no one has done it yet. However, I haven't been reading up for a few years so I might have missed it. It's 0300 I've been drinking and I have an Internet connection. :-P
  • Rather than using the amplitude and frequency of electromagnetic waves, they're using the polarization of the wave to carry the signal. Such a method offers a novel and elegant method of secure communication over fiber optic lines.

    Or... you could use one of the numerous software packages that already exist to "encrypt" your data.

    • Yeah, but then you have to have a trusted method of passing keys. This is a really good method of doing that.
    • Sure you can encrypt the data, but if the eaves dropper is capable of capturing the data stream then they can then use a computer to crunch it until it can be decoded. This solution would act as another level of security. Before the eaves dropper can decode the data they first have to understand what the polorization pattern is.

      Of course, there is nothing stopping anyone coming up with hardware that would record this and then allow the decoding. Though this is where is becomes interesting: imagine if you rotate the polarization of the data through 360 every second, you would then be able to to add add perpendicular signal with junk data - which polarization should the eaves dropper being listening to?

      Security is like a fortress, the more walls you put up the harder it is for the enemy to take control. If you don't deal with security breaches then the enemy can get through with enough work. When it comes to computing the more barriers you put up then more expensive hardware is need by the attackers, so you end limiting the threats to a handful who you can easily watch out for.

    • ...Until the day they figure out how to crack primes, that is.

  • Quantum Cryptography (Score:5, Informative)

    by kovacsp ( 113 ) on Monday August 19, 2002 @03:07PM (#4099928) Homepage
    Quantum cryptography uses the polarization of light to transmit provably secure information. The trick is that when you receive polarized light, if you pick the wrong polarization there's a 50% chance that the light will spontaneously flip to that polarization. Thus, unless you know the correct polarization sequence (the key), as you receive the light, you will not be able to intercept the communications under even the best of circumstances.

    This isn't exactly new either. Its been around since at least the 70's.

    More info:
    http://www.cs.mcgill.ca/~crepeau/CRYPTO/Biblio-Q C. html
    http://www.cyberbeach.net/~jdwyer/quantum_cr ypto/q uantum1.htm
    • The trick is that when you receive polarized light, if you pick the wrong polarization there's a 50% chance that the light will spontaneously flip to that polarization. Thus, unless you know the correct polarization sequence (the key), as you receive the light, you will not be able to intercept the communications under even the best of circumstances.

      FYI, for those not owning photon transmitters/receivers, it might be interesting to know of its vague relative, a software method of communicating confidentially over an insecure link, called Chaffing and Winnowing [mit.edu]. It, too, is based on mere plaintext embed into random noise with keys for the sender and receiver to recognize the right packets off the stream. Unlike in quantum transmission, the participants to the protocol won't notice someone sniffing but the changes for the sniffer to manage to pick up the right packets is near impossible in both cases.

    • Bzzzt.

      We need a 'Just plain wrong' moderation.

      As many others have typed, this is not quantum crypto.

      • I understand that they're not doing quantum cryptography, however its a different application of the same principles involved in the aforementioned. Not so wrong, am I?

  • And I always though copper was secure... (Score:3, Funny)

    by nufsaid ( 230318 ) on Monday August 19, 2002 @03:07PM (#4099935)
    Because it was harder to tap than string between cans.

    • Re:And I always thought string was secure (Score:1, Funny)

      by Anonymous Coward

      Because it was harder to tap than two guys yelling across the yard at each other.

  • Fiber Optic will soon be tapped..thanks to NSA (Score:4, Informative)

    by i_want_you_to_throw_ ( 559379 ) on Monday August 19, 2002 @03:15PM (#4099988) Journal
    Of course I always thought that fiber was always pretty secure anyway since it's a lot harder to tap than copper

    Boy did you think wrong. The USS Jimmy Carter is being retrofitted just for the purpose of tapping fiber optic cable [com.com].

    • The USS Jimmy Carter is being retrofitted just for the purpose of tapping fiber optic cable.

      Yeah, what is that supposed to contradict? That fiber is "pretty secure", or that it's "harder to tap than copper"?

    • Thank god for the spammers. All of the crap they are sending out is making more muck for the NSA to go through to get to any actual information, thus protecting our civil rights because they won't have the time tap into what is actually important. GO SPAMMERS!
    • Then they should rename USS Jimmy Carter to USS Richard Nixon or maybe USS Deep Throat :-)
    • Well yea and?

      We already know fiber can be tapped. The question on whether it is "more secure" is whether the total cost in resources (manpower, equipment cose, time) is greater for tapping fiber than copper. If so, then it is more secure.

      Thats the real metric.

      If you are transmitting data that is worth it to the people in ctonrtol of the USS Jimmy Carter to intercept, and you are sending it over fiber under water, then damnit, you had better take more precautions. Security is risk management afterall. Security measures only need to be adequet to manage the risk.

      -Steve
    • I wonder why people can't get even the VAGUE details right.

      The modifications to the JIMMY CARTER are being done in new-construction, a modification to SEA WOLF design. It's an expensive change, sure. But it's not a retrofit. What PARCHE got was a retrofit.
    • Leaking information about interception methods is a federal crime punishable by imprisonment.

      How long till speculating on the means are punishable? This shit's not rocket science. Get the fiber, make a tiny scratch in the suface. Focus a detector on the scratch as it reflects the signals. You are done. As for the polarized gadget, it looks like you might have to set up a beam splitter and figure out how many angles they have set up. It's more complicated by not impossible.

      Of course, all of this has the ring of Big Brother's underground mole invasion device. Why would you go for a calble under the sea when you could just tap a silly desktop or phone line of interest instead? Kind of like traveling underground when you could just fly. Your tax dollars at work! Buy your 2.4 billion dollar submarine and tap cables today.

  • It's like the FM radio of fiberoptics.

  • That's OK (Score:3, Funny)

    by Craig Maloney ( 1104 ) on Monday August 19, 2002 @03:19PM (#4100019) Homepage
    Why go through the trouble of intercepting it at the fibre level when we can just intercept it near their WiFi stations?
  • with an old school flava of R@y B@ns.
  • Communicates so good you forget the.. the.. ?

  • Ok, fist off all, let us get this straight, this is in no way quantun encryption. although both use polarization, that is were any similarity ends.

    Then, after explaining exactly how a remote site extracts the signal, the offical release says: "This is quite a clever method, which hides the signal in noise," says ONR science officer Mike Shlesinger, who oversees the research. "It provides a definite advantage over direct encoding of polarization, leaving an eavesdropper only chaotic static, and no means to extract the signal." Hiding a signal hardly makes it secure, and certainly does ot do it after you have just told the world how you are hiding it and how you recover it! I wonder if I can get my tax money that was wasted on this back?

  • Polarized light can be seen by any observer not using a polarizing filter, so how are they going to prevent people without the special hardware from intercepting stuff?
  • Bruce Schneier gives a good overview here. [barnesandnoble.com]
    The table of contents is here. [counterpane.com]

  • No Security Here (Score:2, Informative)

    by muerte24 ( 178621 )
    to intercept the signal, you simply tap the fiber and split a small portion of the beam into your copy of their device.

    their "descrambling" method doesn't sound hard - you take the light you receive and send half through a delay loop equal to one circuit through the originating ring laser. then you compare the two signals to obtain the data.

    the only eavesdropper this will thrwart is the guy who uses only intensity (and not polarization) measurements. communication using "Polaritons" has been around for a while.

    the easy way is to put your light through an birefringent crystal and modulate the input voltage - this produces a change in the polarization you can read out with a simple polarizer. the problem is, when you try to change the phase on a photon fast (like for data transfer), you screw up the frequency. and by screwing up the frequency you reduce the gain of your doped fiber amplifiers and you crowd signal space for other colors (although not much, admittedly).

    conclusion: this is useless for sending obscure data. hiding your data in noise is useless if everyone knows how to remove the noise.

    muerte

  • Info 'bout fiber... (Score:2, Interesting)

    by Anonymous Coward
    Fiber is certainly not an easy thing to tap into. Ends of the fiber have to be ground just right for the light to traverse w/o loss. Also, fiber doesn't just 'go down', especially for brief periods of time, most of the time fiber goes down because some yahoo construction worker digs where they shouldn't (or they get bad mapping info, something more common than you'd believe). Many fiber routes are redundant (2 points of entry into a building (in case of yahoo worker previously mentioned), and information travelling both ways along the fiber), but I imagine most organizations who've dropped that much money for fiber (and we're talking thousands to tens of thousands per mile (as of 2 years ago)) keep a pretty good eye on their investments.

    As for knowing what fiber goes where, again, good luck getting the info. I worked for a fiber optic mapping company for some time (hence why I'm posting AC), I've seen some of the maps and info the companies have for their -own- networks. Many companies are in the process of digitizing their maps, but most often the ones they have now are paper, fairly cryptic, with only one/two people really being 'in the know' as to what they mean, per. region.

  • in Carl Sagan's _Contact_ utilized polarization modulation to encode part of their message. Google cache of a page discusing it is here [216.239.37.100].
  • Making the wire hard to tap is useless when you're in the military. Once something is in widespread enough use SOMEONE will make a tool for breaking it. I'm sure there's a "fiber tapping kit" out there that every government uses some variant of. It might be hard, but it's not impossible, and that means it's going to be done.
  • Can someone more versed in optics explain to me why you can't just use FTIR (picking up the evanescent wave) to tap into a fiber without actually splicing it? It seems like it should be possible, and you wouldn't have to damage the fiber except for removing the cladding...
  • not really. it's just that you're more comfortable
    with a soldering iron than a butt-polisher.
    i readily admit that an optical amplifier has at
    least one more stage than an electrical one, but
    c'mon, that's just one more component on a circuit
    board, if you're using an ASIC for the core.
    being less popular doesn't really mean it's
    *harder*. but i confess it does mean the
    probability of tap is lower.

    But doesn't everybody use crypto for sensitive
    data? That being the case, physical vulnerability
    is down in the noise. Spend your time and money
    on key management instead, and you'll be safer.
    At least until those quantum well devices start
    coming out...

  • I must really be missing something here, because I don't see how the polarization plays any important role in securing the transmission.

    It seems to me that you could do the same thing with ANY modulation mode: just mix two copies of the signal, one delayed by 239-nanoseconds apart, with a noise background, and extract the signal by correlating it against a 239-nanosecond-delayed version of itself.

    Seems like a fairly weak kind of encipherment, since all you need to know is what kind of modulation has been used and what the delay is.

    Seems to me that even the kinds of ciphers I used to read about in junior high school (Vigenere, etc.) would be just as secure if not more.

    I don't see much security just from a novel means of modulation. I mean, sure, if all anyone has are FM receivers you can send secret messages by using AM modulation. And an ordinary 2400 bps modem is pretty secure if all you can do is listen to it with the naked ear...

  • It's a clever technique. Essentially, it's crypto
    in which the key is the ring radius. But the
    time to defeat for reasonable ring sizes will not
    be very great. Still, it's a good hardening layer
    on top of conventional cryptography.

  • I have a question on that anyway.

    I know you can't put a quantum crytography signal through an EDFA, thus making lots of copies of the signal photons and giving you enough chances to beamsplit and measure the polarisation states.

    How do I know this? Because it wouldn't be a good system if you could. What I want to know is why doesn't this work? What fundamentally stops this happening?

    It can't be that Eve might NOT split off all but one of the amplified bunch of photons for any individual bit and thus giving the game away to Alice because Eve could just retransmit from scratch.
    Is it instead something about the beamsplitting process? I seem to remember a presentation at Uni from one of the theory guys which implied that 2 identical photons (such as the original and a copy out of an amplifier) are not independantly beamsplit but that instead take to reflection or transmission output path from the beamsplitter as a pair.
    Is that right? Or is it something else entirely.

    If there is anyone who can reply, that would be great. I know all the experimental side of these things, I built Erbium fibre ring lasers and looked at their output polarisation states for my PhD. I just don't have the quantum theory knowledge.
  • It looks like if the cable it tapped, the other end will know about it. That is moreimportant t than encrypting the dataflow.

    Years ago I looked at doing a type of computer generated hologram. It involved something like ray tracing backwards. So instead of 1024x768 pixels and figuring out where the light went, you had a 1024x768x10k and you had to backtrack the other way and add up all the wave interference. Looks to me like you could throw in one more axis for polarization to this system and you'd have it cracked in no time --assuming you do the all the calculation in no time :-) I would take a guess that it would only take about 6e25 vector calcs per bit change so about the same as 80 bit encryption per bit.
  • This reminds me of Sagan's "Contact", where the ET's used polarity modulation to embed the primer onto their radio signal (which was already packed with three or four different datastreams). The humans struggle to decode the message, until somebody decides to check the polarity...

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