I’ve touched on the Lilly wave before, in the context of lifehacking stuff. (It was invented in 1955 as a way of doing very long-term cranial electrostimulation without damage to the brain. It’s simply a positive pulse followed very quickly by a negative pulse, in order to leave any neuron it touches the same as before.)
The interesting thing is that its inventor, John C. Lilly, went on to become a well known dolphin researcher. (And a psychonaut, but that’s beyond the scope of this discussion.)
Now the concept has turned up again — in what researchers describe as “Dolphin-inspired* radar.”
In a nutshell, the idea is a radar system that sends out two pulses in very rapid succession, instaed of one. The second pulse is a mirror image (phase inverted) of the first.
The magic lies in the way the relationship between the two pulses changes depending on whether the target responds in a linear or nonlinear manner. A linear target, like a piece of aluminum or soil, leaves the pulses unchanged.
Take the first pulse and sum it with the second, and the two pulses cancel… you get zero signal. Subtract the pulses, and you get twice the signal.
Now, if you have a nonlinear target… like a diode, or a bugging device, or a cell phone… something different happens.
Remember when I said summing the first pulse with the second would give you a zero signal? Well, I kind of lied. That only applies to the fundamental frequency. When we’re talking about higher harmonics — the “overtones” of twice the frequency, or higher — the relationship is reversed.
With a higher harmonic, subtracting the pulses causes them to cancel. Adding gives you twice the amplitude.
Okay, now there’s one more thing to point out. Nonlinear devices when struck by a signal will reflect back higher harmonics with much greater intensity. In other words, if you swept a beam of pure 900Mhz radio waves across the room and looked at the return signal on your spectrum analyzer… you’d see a sudden “spike” at 1800Mhz when you swept the beam across a diode or your cell phone.
This property has long been used to find bugs. And, it causes some interesting things to happen when you’re using two pulses. Let’s bring things back around…
Since the harmonic is stronger when you’re “pinging” a nonlinear target, what happens when you combine the two pulses? Adding them no longer produces a value that’s quite so close to zero… now the 2nd harmonic is strong enough that it occupies much of your measurement.
In fact, if you use filters to isolate out the fundamental, second, and third harmonics, you get even more precise results… you can now “see through the clutter” and mark which of the points on your radar screen are regular metal and which are electronics.
Which is pretty useful, when the object in front of you is a coffee table, that seems to have something electronic embedded in the middle of it…
Unfortunately, doing this like they do in the paper is expensive, requiring big shiny DSO’s. Is there an easy homebrew version? Maybe. One Slashdot commenter suggests a T-connecter and a short length of unterminated coax will do all the subtracting you need… just adjust the inter-pulse duration until the (inverted) reflection off the unterminated end cancels out the incident second pulse! **
Integrating over the whole business (maybe using a fast diode detector) then gives you the signal you need (plus the first pulse, which is constant).
* Dolphins don’t actually use the concept. The researcher just sat down and asked himself, “if I was a dolphin and had to navigate through bubble-filled water, what kind of sonar signal would I use?”
#badBIOS: the Boot CD test only works if the OS is “something different.”
“Btw it seems the boot from cd test for #badBIOS only works with different OS. Pick something weird.”https://twitter.com/dragosr/status/394869042227339264
One example of the malware is available here: https://malwr.com/analysis/M2ZiOWVmN2M3MTE3NDEyNWI2OWY1YWY3Zjg0ZDg4OWY/
NSA in Berlin: What does an NSA embassy antenna look like? Here’s an example. That’s a REALLY WEIRD feedhorn… either a dual-polarization multiband Yagi if such a thing can be done, or something very very different. http://cryptome.org/2013/10/cia-nsa-scs.htm
Yes, it’s a serious issue, but I kind of want to make one of those black-bordered meme pictures for this. “Espionage from an embassy? NO WAI!!!” Nevertheless it’s clear Germany is being spied on more than most countries — if only by virtue of the NSA having two Special Collection Service bases, one in Berlin and one in Frankfurt.
And that isn’t even taking into account the absurdly overmassive US intelligence presence in Wiesbaden (Domscheit-Berg’s home town, oddly enough, soon to become quite openly the NSA’s largest installation outside the UK), Darmstadt/Griesheim, Heidelberg, and just about everywhere else in southern Germany. It’s been said Germany has a larger American presence than any non-US country except England, and no doubt this is part of the reason German finance minister (and former internal security minister) Schaeuble likes to say Germany has at no point been a sovereign state since 1945. http://www.spiegel.de/international/germany/cover-story-how-nsa-spied-on-merkel-cell-phone-from-berlin-embassy-a-930205.html
There’s now a Snowden defense fund webpage: http://freesnowden.is/
“The technique uses a signal
consisting of two pulses in quick succession, one identical to the other but phase inverted, to distinguish nonlinear scatterers from linearly scattering objects .[…]
The envelope of the summed [received] signals is smoothed to form P+ . The subtraction of the second
echo from the first produces a signal with doubled amplitude (i.e. Y1 (t) − Y2 (t) = 2Y1 (t)), the
smoothed amplitude of which is denoted P− . The same pattern of suppression on addition and
enhancement on subtraction occurs for odd-powered scattering whenever P+ and P− are formed.
However, the contributions to the reflections that are produced by even powered scattering follow
the opposite trend, being enhanced when P+ is formed and suppressed in the signal P− . This
applies not just to the steady-state linear scatter, but also to linear scatter associated with ring-
up  and ring-down . Because the trends in suppression and enhancement are opposite
for odd (including fundamental) harmonics and even ones, then, for example, comparison of
the amplitudes of scattering structures in images of P+ and P− for the same field of view allows
identification of linear scatterers from nonlinear ones and further distinction between those which scatter particular (e.g. odd or even) harmonics from those which do not. “