A New Unbreakable Code System

Discussion in 'Current Events' started by Mr. Anderson, May 5, 2005.

  1. Mr. Anderson Moderator emeritus

    Mr. Anderson

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    #1
  2. robbieduncan Moderator emeritus

    robbieduncan

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    #2
    From what I understood this is not a code system, more a transmission method. It does beg the question what happens if the read end misses a photon? I assume the transmission protocol must have quite a lot of error checking built in...
     
  3. kylos macrumors 6502a

    kylos

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    This system would seem to be unstable over relatively long distances, since some slight leakage is expected when transmitting over fiber. This would likely require the signal to be interrupted more frequently to check for errors and to realign the signal.
     
  4. jsw Moderator emeritus

    jsw

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    #4
    Cool. According to this article, this new single-photon method prevents the man-in-the-middle attack developed for prior quantum-entanglement-based schemes.

    Of course, quantum entanglement (in its original, multi-photon form) was at first considered unhackable, so one must wonder how long this new method will be seen as such.
     
  5. Mr. Anderson thread starter Moderator emeritus

    Mr. Anderson

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    Until someone learns how to just observe the photon without removing it from the stream :D

    D
     
  6. Chappers macrumors 68020

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    Don't worry - Microsoft are working on it.
     
  7. Wes macrumors 68020

    Wes

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    #7
    Hmm isn't that very hard to do as a result of Heisenberg's uncertainty principle? The process of detecting such a tiny mass is going to deflect it to a huge degree, hence alerting to a hacker intercepting the signal.
     
  8. fedora macrumors member

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    No apple are - OS X Schrödinger's cat, for release on the first desktop quantum computer. :D
     
  9. clayj macrumors 604

    clayj

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    It's IMPOSSIBLE to do, unless Heisenberg was wrong.
     
  10. fedora macrumors member

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    #10
    If anyone want to learn more about quantum computing/physics come and do a search on this forum I post on: www.physicsforums.com this topic and it's link too LQG have been discuss in depth.
     
  11. Wes macrumors 68020

    Wes

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    #11
    Or unless we find smaller particles to detect photons with...
     
  12. fedora macrumors member

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    #12

    What do you mean "smaller" photons have no dimensions? only mass as a product of velocity.
     
  13. clayj macrumors 604

    clayj

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    They still have size, though, right? A point particle (dimensionless) with mass would have infinite density (weight per unit volume), and that doesn't make sense.

    I think he meant trying to use quarks or even strings to detect and "read" a photon's state without altering it. Of course, if you could do this, the resulting apparatus would be so large and require so much energy to operate that everyone would know what you were up to.
     
  14. admanimal macrumors 68040

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    #14
    The retail box contains a single dvd that is both blank and contains the final version...you don't know which you get until you open the box.
     
  15. cr2sh macrumors 68030

    cr2sh

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    #15
    God I really hate threads like this. Everyone has to whip out there college physics notes and try to pass judgement.

    Aren't there insanely cheaper and simpler "unbreakable" codes?
     
  16. Shaun.P macrumors 68000

    Shaun.P

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    #16
    Anyone in here read Dan Brown's 'Digital Fortress'. It's about a code that cannot be broken - I'm in the middle of reading it!
     
  17. clayj macrumors 604

    clayj

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    Yup. The good ol' one-time pad. Use the cypher once, then throw it away. The people at both ends of the communication have the same pad. Since the cypher is NEVER reused, a pattern can't be established by anyone who's monitoring the communication, and therefore they can never decypher it.
     
  18. admanimal macrumors 68040

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    #18
    Well since we're getting all theoretical here, it's worth pointing out that the varying levels of "unbreakableness" achieved by modern (non-quantum) cryptography are all based on the assumption that P does not equal NP, i.e. that there are certain reasonable things that we would like to compute efficiently, but can't seem to (the prime factorization of an integer being the most relevant). The disturbing thing is that it is unknown whether it is truly impossible to compute these things efficiently or whether we just haven't figured out the trick to it yet. If someone does find the trick, then most modern encryption techniques would fall apart.

    So I don't get attacked by any theoreticians hanging out here, I should point out that finding a polynomial algorithm to solve the factoring problem (the NP problem most relevant to encrpytion) does not prove that P=NP, since it is not NP-complete.
     
  19. MongoTheGeek macrumors 68040

    MongoTheGeek

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    #19
    Or goes through the trouble of replacing it...
     
  20. fedora macrumors member

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    I know this is a bit off topic,

    You are correct, it's correct to think that photons do have "size". I said they did not because the physics gets difficult. A photon has a perfectly well-defined wavelength only when it's in a momentum eigenstate, i.e. when it has a perfectly well-defined momentum (and energy). This never happens. A photon is always in a superposition of momentum eigenstates:

    [​IMG]

    The only quantity that we might want to call the "size" of the photon is the width of the Fourier transform of the momentum-space wave function, f, i.e. the uncertainty in the photon's position. This uncertainty could be anything between zero and infinity. Since it can be arbitrarily close to zero, it makes sense to call the photon a "point particle".

    However, if we assume that the uncertainty in momentum is proportional to the magnitude of the momentum (which is the only thing we can assume if we know nothing about the state), the uncertainty in position is proportional to Planck's constant divided by p (the magnitude of the momentum). Since p is inversely proportional to the wavelength, the uncertainty in position is proportional to the wavelength.

    So it makes sense to think of the wavelength as the "size" of the photon (or at least as something proportional to it). This may seem strange, but it is at least consistent with e.g. the fact that microwaves (with wavelengths of order 1 cm) won't go through a metal net with millimeter-sized holes (like the net that covers the window of your microwave oven), but they will go through a net with much larger holes.

    So photons do have "size" but it is not size as in a lump.
     
  21. yellow Moderator emeritus

    yellow

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    #21
    I wonder what they would have found if they'd added a bag of microwave popcorn to the mix.
     
  22. robbieduncan Moderator emeritus

    robbieduncan

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    #22
    Yes I've read and. And I don't think I'll ever forgive Dan Brown for writing such a terrible book. Probably the worst thing I've read in the last 2 years :mad:
     
  23. Nickygoat macrumors 6502a

    Nickygoat

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    #23
    They are unbreakable on a depth of one (used only once) but are unsuitable for mass market systems. They are also vulnerable to social engineering ie. capturing one of the one time pads.
     
  24. cr2sh macrumors 68030

    cr2sh

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    #24
    Exactly the system I was thinking of... the system that killed the Rosenbergs.

    [​IMG]
     
  25. clayj macrumors 604

    clayj

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    Well, that's true for ANY system. You have to keep both ends of the communication secure.

    Tom Clancy described a (fictitious) one-time pad system called Mercury in one of his novels... rather than a physical pad of paper, the "pad" existed on a CD-ROM and was generated using atmospheric radio noise, so that it was truly random. (If you let a person come up with the cypher, they'll unknowingly apply a pattern to it given enough time.) Two copies of the CD were made... one for the base, and one for the remote location. All transmissions were encrypted/decrypted using the contents of the CD, which was then destroyed once all of the bytes on it were used.

    Using a dual-layer DVD (8.5 GB of random bytes) at both ends, you could encrypt/decrypt a HELL of a lot of e-mail...
     

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