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Optical Cryptography
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."
If you're interested in how they syncronize the noisy lasers, here is a shortcut to the non-linear faq... a bit of easy evening reading for your enjoyment.
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 ?
Maybe I'm completely off here, but if you're using noise interference, wouldn't that be sort of wasting bandwidth? This is a cool technology, I wonder if there would be a way to mask a signal and at the same time run multiple signals, so you could essentially split the information through a long pipe (like the laser) using the chaotic noise, and each would be able to be filtered out (at some sort of router) and sent to various places accordingly. Seems it would be much more efficient to carry information that way.
You could also image doing this with regular any noise and random observations. Like solar observations, for instance or other space observations. Could even be based on traffic to specific web sites....
The trick to all noise-masking techniques is for YOU and YOUR PARTNER to have the same set of noise and NOBODY ELSE to have it.
Use a well-known public noise source and a link to that source becomes the key which decrypts all your traffic.
Oops!
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
This is essentially a one-time pad cipher where the pad is the length of the message and then (in the digital world) they XOR the pad with the message and send them both. For fiber optics, they probably do a similar transform, but instead of XOR they probably just a straight add, modulo some appropriate number.
--sam
--sam
Any technology distinguishable from magic is insufficiently advanced.
Great... now the RIAA/MPAA will be breathing down our necks for bypassing "noise-based-encryption" protection schemes every time we shield an audio or network cable...
The encryption in cryptonomicon was a one time pad. The pad was implemented as a record, but the concept was the same. The fact that the conversation could only last as long as the record and each record was only used once is indicative.
But then, perhaps the lasers could be considered an infinite one-time pad? Of course, if anyone else is listening to the synchronisation codes, couldn't they themselves end up with a synched laser too?
As a form of encryption, this doesn't appear (to me) to be incredibly useful to the average person. It doesn't secure the communication, only the physical connection between the two points. However, it would work for keeping snooping foreign governments from listening in on international traffic on submarine cables. Or nasty pirates from splicing themselves into the cable TV network...
This form of chaotic synchronizing communication works by a dynamical systems property. It seems like magic but it is not really.
It relies on the effect of chaotic synchronization. That sort of amazing fact that even though you can have a dynamical system that is continuously unstable in 'some degrees of freedom' making up the chaotic system the combination system of transmitter and receiver can still be stable in the 'transverse' direciton to the synchronization manifold.
All communication systems work by synchronization whether implicitly or explicitly. Here you will explicitly have chaotic oscillators as both transmitters and receivers. Yes, radio is like this too, you have a linear oscillator in the transmitting tower and an oscillator in your RF circuit in your receiver and their electric fields will synchronize the receiver's oscillator to the transmitter.
The trick is how to add in modulation and demodulation that does not destabilize the system and still permit reconstruction of the transmitted information.
All chaotic systems essentially have some sort of nonlinear feedback. The trick that seems to work very frequently with optical dynamics is to mix in some of the transmitted signal coming over the channel with the self-regenerated system at the receiver. In previous work with fiber optic ring laser it really was literally mixing optical signals, in the thing I did it was mixing in electro-optic electrical feedback signals; more like mixing intensities.
It turns out that a fairly generic form of dynamics often seems to work.
I worked on this project from a theoretical modeling level with Jia-Ming Liu's group at UCLA.
(We're at UCSD not UCLA).
I'm not sure what this new work is about but in the version that I did there was no significant role for the dynamics or properties of the fiber optics in the creation of the chaos or the demodulation.
It will a very significant amount of engineering to make this fully practical and find all the good properties but that's true for every advance.
Oh yeah...Johnny Mnemonic! Yeah, when he was picking random images for the data to encrypt it. I find it strange that something from such a mediocre movie gets to actually be applied as technology. (Then again, the whole point of the movie was its neat ideas.)
Why didn't somebody think of this before?
Zodiac Survey
We had a link with the British in the War that would use a disk of noise to overlay a signal on top of communications that would be un scrambled on the other side by the same wheel running on at the same time. The more things change, the more they stay the same.
Check out the NSA's explanation
Previous Slashdot Story
How does one hide messages in reandom noise, though? Would it work to LZ-compress them, to make them appear random?
LZ+Huffman (i.e. deflate, the core of gzip and pkzip) works, but you get more compression in a Burrows-Wheeler based scheme such as bzip2. More compression => more entropy per coded symbol => more resistance to known plaintext attacks.
Will I retire or break 10K?
This technique is actually very old, though it wasn't used bit by bit. You're inserting null terms into the cypher stream. Prior to modern cryptological methods nulls were fairly popular, but the technique has fallen into disuse because of its increasing the message size, and because 1:1 stream cyphers are SO much more convenient. Besides, the new cryptosystems are unbreakable, right? Right?
Even having a small multiple of nulls to significant elements increases the complexity of calculation exponentially. For example, a 1:1 proportion of null bits in 512-bit blocks. The result is a 1024-bit blocked key stream. You can't do any sort of intelligent analysis of the stream unless you can figure out which bits are significant, and there are 2^512 possible permutations of significant and garbage bits for each block.
That's close enough for slashdot!
For communication it is one-way synchronization with unidirectional coupling, not the mutual coupling which is more well known in math and physics.
The important point is that the chaos and the 'keys' and the message can all be combined nonlinearly.
Eavesdropper C would need the same chaotic system with the same settings up to some tolerance. Notice that robustness to attack is thus inversely proportional to tolerance to mismatch.
The issue of security is not directly addressed by chaotic communication.
Chaos may be an opportunity to do things other than classical encipherment. It may be like CDMA spreading a signal over a wider frequency band. It may allow you to use cheaper devices or those running past their "normal" tolerance bounds if the requirement for linearity is no longer a factor. It may mean lots of different things; the general point is a greatly increased flexibility and the potential to try widely different kinds of transmission methods. Linear signal transmission is kind of boring, there's AM, FM and minor variations upon those.
However, it may be that some digital ciphers have properties similar to chaotic systems and people are starting to investigate this connection at a different level. that is more mathematics now than communications engineering.
By contrast, a theoretical one-time pad is theoretically provably uncrackable - if you really do have uncorrelated random bits for your pad, and you really only use them once, it's perfectly secure, and even knowing N-1 bits of a message tells you nothing about the other bit. In practice, source of random numbers aren't always perfect, and sometimes people cheat and reuse pads - the NSA's "Venona" crack of Soviet crypto primarily succeeded due to rampant reuse of pads by sloppy crypto users, though I think they also found some non-randomness in the pads that they could exploit a bit. But this optical system guarantees that if you know the initial conditions, you can use the first N-1 bits of a message to predict the next one, and sometimes you may be able to deduce those initial conditions closely enough to crack the system.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
Prof Alan Shore has done some work simmilar to this at Bangor university
Anyone quoted by a reporter knows how little they understand
Don't believe what you read is the truth.