Holographic Sonar Cryptography

Atomic Snarl writes: "New Scientist.com has this story on how to encrypt a underwater sonar message using multiple sound path timing. By detecting and adapting for the current variations on underwater sound channels, the transmitted message can be received intelligibly only at a single point. This holographic approach suggests a method of web encryption using multiple hop paths and ping times to create a message which can only be decoded when received at a specific target node!"

Speed of sound versus ping times

[Chiasmus_]

It seems to me that the speed of sonar through water is a physical certainty; that's why we can accurately use it to detect the distance from an object.

Internet traffic is another matter. If I tried to use a ping time to measure the geographic distance to another server, I'd be about as scientific as the Slashdot poll.

Am I wrong, or could internet latency give or take 100 ms or so from a ping, rendering the encrypted message readable by.. no one?

That's refreshing...

[John Leeming]

...which leaves the question...

Does this mean that they need more "big rocks" under the Great Lakes, or can they still use the same "big rock" to use this?

Interesting, but too scientific?

[friday2k]

I think the idea Edelmann is pursuing here has some very interesting implications but also limitations. I wonder how stable the environment on greater distances might be, current, the seabed itself, and other environmental influences. The same goes for the suggested idea of using ping times and number of hop points to encrypt a message. These are highly unstable factors and in order to encrypt the message the environment shall be the same for both sides for the time of the communication flow. But I am also not enough cryptographer to really tell. Maybe others can shed some light on this?

Re:Speed of sound versus ping times

[c_ollier]

I think the speed of sound in the water has small variations due to pressure & temperature shifts. And error checking & correcting would be difficult, as these variations would make the message unhearable.

To me, it seems as hazardous underwater as on the Internet.
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Covert Operations

[DMouse]

So let me get this straight, they are suggesting that a submarine can communicate securely with something else in the water ... by being really noisy.

I can see that going down a treat when a sub is trying to keep itself invisible.

One time pad

[Anonymous Coward]

So they've basically reinvented the one time pad, just using the environment as a key...

Only in the real world

[joe_fish]

It won't work on the net well, and there are problems with the idea in the real world too.

In effect the sea floor and positions of sender and reciever are acting as a secret key. They 'encrypt' the messages and you can only decrypt if you know the secret key in enough detail - i.e. you are the reciever, and the working with the sender. However the snooper in *theory* could decode the signal if he knew enough about the sender/reciever/sea bed, and could do some farily complex maths. How complex the maths is says if it will work in practice. But given that computer can model huricanes, I would guess that modeling the sea bed is plauible.

In the virtual world though all bets are off. The terrain is very mappable, and fairly simple. So if the problems of varing ping times can be worked out the encryption is very easily broken.

I wonder if the sea bed version stops working if the tide changes.

Re:Sonar audio pollution more important

[Phanatic1a]

You don't have a cite for that, do you?

Oh yes you CAN intercept it along the way

[PD]

Theoretically, at least.

In astronomy, the coolest research is in adaptive optics (do a Google search and you will be reading in fascination all day). Here it is in a nutshell, step by step:

1) The earth's atmosphere is turbulent. That turbulence causes the images of stars to dance around in telescopes, making the image all fuzzy. This is what causes the stars to twinkle when you look at them. Avoiding this problem is the big reason why the Hubble Space Telescope gets such amazing photos when it is much smaller than the largest telescopes on the Earth.
2) How to fix this problem without launching telescopes into space? Adaptive optics, of course. If you can flex a telescope mirror into exactly the right shape, you can compensate exactly for the distortion that turbulence introduces into the image, removing the majority of the noise from the signal. Suddenly the image becomes almost perfectly clear and steady, not fuzzy.
3) We know that stars look like points of light, even through the largest telescopes. When we receive a fuzzy image, a very fast computer figures out what shape a mirror would have to be to focus that fuzzy image back into a single point of light. That star is called a reference star. Any interesting objects close to that star are also therefore made clear.
4) Commands are sent to mechanical actuators on the back of a mirror that deform it to the correct shape to focus the reference star. This happens very quickly, so the resulting image is steady and sharp, despite all the turbulence in the atmosphere. Neat trick.

OK, so that's how it works.
You can do the same thing to submarines too, if you know what they sound like. The submarine's sound becomes the "reference star" in this case. When you receive the garbled signal, you might be able to correct it based on the sub's sound. If you apply that correction to the message as well, you might be able to hear the message.

This has a lot of problems, so practically it wouldn't work. For example, the easiest way to defeat the intercept is to change the noise that your sub makes, maybe with a random noisemaker. But that makes your sub less quiet. Also, the person trying to make the intercept would have to be listening to the sub before the message is sent, because once the message is sending, that would make the sub a random noise and you couldn't focus the sound. And, since the turbulence conditions change (I don't know how fast), over time your ability to focus the sound into a message would steadily degrade. The sending submarine would only have to figure out how fast the sea conditions are changing, and only start sending the good parts of the message after you've lost your ability to focus the sound.

This wouldn't quite work on the web.

[BlueTurnip]

If one reads the article carefully, one would discover that this "encryption" technique makes use of the wave nature of sound to both obscure the data in transit, and reconstruct it at the final destination.

There is no analogy for web traffic which travels over IP which is sent as discrete packets of bytes. They resulting packets cannot be made to interfere with each other at the destination to produce plaintext, nor do they interfere and reflect and become distorted in transit!

The closest analogy would be to split a message into many small parts and send them along different paths in the hopes that no one could catch them all in transit, but then timing isn't really an issue at all as others have suggested. Also, anyone bugging your connection to the internet (your ISP for instance) could still catch all the packets, ditto for the source. Some have suggested splitting keys and sending some parts by snail-mail, others by FedEx, others by e-mail to different accounts which you read on different machines, and that is really a form of security through obscurity, not encryption, whereas the sonar technique is more like encryption in that even if an adversary knew that information was being send and knew from where, they could't recover the plaintext unless they were at the target location.

Perhaps quantum cryptography is a better analogy to what's going on, but it's not a perfect one either as there are fundamental differences between accoustical waves and quantum wavepackets.