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Optical Cryptography

Posted by timothy on from the this-little-light-of-mine dept.

chill writes: "In Cryptonomicon, Neil Stephenson wrote about Bell Labs' research into using static, or chaotic signals to mask communications. A message would be generated, then the signal masked in noise. Someone on the other end would subtract out the noise to get the signal. Works great if both ends have the exact same noise. Now, Jia-ming Liu, professor of electrical engineering at UCLA, is giving a presentation on doing essentially the same thing using OC-48 (2.5 Gbps) optical circuits. The presentation will be at the upcoming Optical Fiber Communications Conference and Exhibit. There is an article covering this and some other nice advances in optical over in Wired."

6 of 158 comments (clear)

  1. steganography ? by sh0rtie · · Score: 3, Insightful

    so how is this any different than steg
    where a message is hidden in noise (the image) then when the image (noise) is subtracted the message appears.

    are we still trying to re-invent the wheel here or am i missing something ?

    1. Re:steganography ? by metacell · · Score: 2, Insightful

      Well, if you use encryption or steganography on a computer, you have to utilize digital techniques, which is timeconsuming. Performance drops.

      If you merely have to superimpose two lightwaves to steganize (sp?) a message, it all goes in realtime no matter how much bandwidth the lightwave carries.
      It's not a digital technique. It uses analog lightwaves.

      So that technique can be used in e.g. optical fibres, so nobody can intercept messages by physically eavesdropping on the fibre.
      I don't think it's intended for home computers. It sounds more like a simple way for telephone companies to protect all the data in optic fibres without going in and encrypting the individual IP packages and such.

  2. Re:Nope: You've just given the bad guy your key. by Bellwether · · Score: 2, Insightful

    This is called traffic masking, and is a useful, known tool. However, it can also be viewed as security through obscurity, typically a bad thing. (tm)

  3. Re:Seems like a waste of noise... by IsaacW · · Score: 2, Insightful

    This is true only if the two waves being added have the same frequency spectra, or if one of the waves is contained in the other in the frequency domain. If you add a 10 nanometer-wide signal centered at 700 nm to a 10 nanometer-wide signal centered at 710 nm, the resultant wave has a bandwidth of 20 nm.

    This wave would take up more bandwidth than either of the other two.

  4. Re:Security through obscurity. by Bellwether · · Score: 2, Insightful

    Well, look at it this way: if your background traffic is random noise, and your "signal" cannot be differentiated from random noise, one must question what kind of signal actually is present.

    It's really, really hard to mask a legitimate messages in random noise and hope that the bad guy won't be able to differentiate the two.

  5. Re:Asymptotic rate is not good enough. by metacell · · Score: 1, Insightful

    Ok...

    So you're saying Rissanen gave the theoretical limit for how quickly a compression algorithm asymptotically approaches maximum entropy in its output, and Context Tree Weighing and other algorithms actually reach that limit?

    Or is this only proven for certain classes of input, like Markov models?