On 2/5/16, Sean Lynch <seanl@literati.org> wrote:
... Radio is being used right now to provide anonymity, but it's being used[1] to hide endpoints similar to the duct-taped payphone trick depicted in Hackers, in order to avoid attacks like the one used to capture Ross Ulbricht without giving him a chance to wipe his computer (they snuck up behind him and pinned his arms, but they would have just rushed him had that not been possible). If you use a device like the ProxyHam and you sit somewhere where you can see it, there's a reasonable chance you'd spot someone who's trying to find you, giving you a chance to hit your panic button and escape.
this assumes you're keeping it under constant supervision, of course :P
The older, lower-tech version of this trick is to use a high-gain antenna like the Cantenna or a Yagi to use a public wifi AP from a stealthy, defensible location. The problem with this is that this presents no challenge to RDF (radio direction finding) equipment designed for WiFi. That's the big advantage of the ProxyHam, since whoever is looking for you probably won't know in advance what frequency you're using. And solving that problem in a general way requires MUCH more expensive gear than just locating WiFi clients.
one of my favorite tricks, but rather rude in spectrum, is setting high power amplifier to maximum. DF tends to see this signal arriving from all around... *grin* this introduces it's own trade-offs, of course.
If you're concerned about someone coming after you with much more capable RDF equipment, you are now talking about LPI (low probability of intercept) communications. This could be something as simple as a longwave infrared optical link, which won't show up on regular CCD or CMOS camera even without an IR filter.
free space optics rides again!! :P
With SDR you might use some form of non-sinusoidal spread spectrum with extremely high processing gain so you'll be well below the noise floor and your carrier won't be recoverable using autocorrelation techniques. Some UWB techniques fall into this category, though because "legal" UWB is required to be confined to a narrower bandwidth, it's probably detectable.
right, UWB is the solution here with privacy and authenticity at the physical layer (not above MAC, or other deferred placement in stack)
It MAY be possible to use SDR to achieve LPI while still remaining within
if you're building LPI, you don't give a fuck about the FCC (compliance). by definition, if they've found you, you fucked up!
Actually, that gives me an idea: MIMO precoding[2] (versus spatial multiplexing, which is useless for your purposes). MIMO precoding devolves to beam-forming in the absence of reflectors like buildings, but in an urban environment, you get a complex combination of signal paths,
MIMO precoding requires a "training" phase where they discover one another by transmitting some easily "locked-onto" signal so that each receiver can find the other transmitter independently.
it is now possible for a professional's budget to accodomate the SDR equipment necessary to do this type of phase sync'ed active beam forming MIMO transmission, and not all methods require the training phase. in fact, omission of this (by out of band training, in a sense) in a method of "keying" phased delivery of UWB MIMO in a way more likely to achieve LPI. synthetic aperature millimeter wave vision systems are also pushing along this boundary, for cross-pollination of suitable phased sync'ed UWB MIMO signal processing. i could go on, if you're curious, but perhaps on another list? :) best regards,
From: coderman <coderman@gmail.com> Sbject: Re: [tor-talk] Using SDR On 2/5/16, Sean Lynch <seanl@literati.org> wrote:
The older, lower-tech version of this trick is to use a high-gain antenna like the Cantenna or a Yagi to use a public wifi AP from a stealthy,
Initially, I was confused about this. To me, a "Cantenna" was Heathkit's name (in about 1970 or so) for a dummy-load built from a1 gallon paint can with a non-inductive resistor inside, immersed in transformer oil, capable of dissipating 1 Kw or so. Showing my age.Now, on Google-search, I see it as an antenna built with a tin can. Jim Bell
On 2/6/16, jim bell <jdb10987@yahoo.com> wrote:
... Initially, I was confused about this. To me, a "Cantenna" was Heathkit's name (in about 1970 or so) for a dummy-load built from a1 gallon paint can with a non-inductive resistor inside, immersed in transformer oil, capable of dissipating 1 Kw or so. Showing my age.
*grin* i suppose i'm old for knowing this technology...
Now, on Google-search, I see it as an antenna built with a tin can.
usually out of Pringles cans in totally ad-hoc fashion :P best regards,
On Fri, Feb 5, 2016 at 10:36 PM jim bell <jdb10987@yahoo.com> wrote:
*From:* coderman <coderman@gmail.com> *Sbject:* Re: [tor-talk] Using SDR On 2/5/16, Sean Lynch <seanl@literati.org> wrote:
The older, lower-tech version of this trick is to use a high-gain antenna like the Cantenna or a Yagi to use a public wifi AP from a stealthy,
Initially, I was confused about this. To me, a "Cantenna" was Heathkit's name (in about 1970 or so) for a dummy-load built from a 1 gallon paint can with a non-inductive resistor inside, immersed in transformer oil, capable of dissipating 1 Kw or so. Showing my age. Now, on Google-search, I see it as an antenna built with a tin can.
Sorry about that. I had initially considered including a reference, but I figured it was an easily Googlable term. Name collisions hadn't occurred to me. My radio knowledge is a mix of modern Ham education and 1950s era Ham education, the latter because those were the books my tiny middle school had in its library :)
On Fri, Feb 5, 2016 at 7:23 PM coderman <coderman@gmail.com> wrote:
On 2/5/16, Sean Lynch <seanl@literati.org> wrote:
... Radio is being used right now to provide anonymity, but it's being used[1] to hide endpoints similar to the duct-taped payphone trick depicted in Hackers, in order to avoid attacks like the one used to capture Ross Ulbricht without giving him a chance to wipe his computer (they snuck up behind him and pinned his arms, but they would have just rushed him had that not been possible). If you use a device like the ProxyHam and you sit somewhere where you can see it, there's a reasonable chance you'd spot someone who's trying to find you, giving you a chance to hit your panic button and escape.
this assumes you're keeping it under constant supervision, of course :P
Indeed. Having a spotter there is probably the best solution.
The older, lower-tech version of this trick is to use a high-gain antenna like the Cantenna or a Yagi to use a public wifi AP from a stealthy, defensible location. The problem with this is that this presents no challenge to RDF (radio direction finding) equipment designed for WiFi. That's the big advantage of the ProxyHam, since whoever is looking for you probably won't know in advance what frequency you're using. And solving that problem in a general way requires MUCH more expensive gear than just locating WiFi clients.
one of my favorite tricks, but rather rude in spectrum, is setting high power amplifier to maximum. DF tends to see this signal arriving from all around... *grin*
this introduces it's own trade-offs, of course.
This is why you use an attenuator. I wouldn't think law enforcement DF equipment would be fooled by such a thing, since for example FCC will often be looking for people who are outputting too much power, which on the ham bands is going to be multiple kilowatts (I think they've mostly given up on CB except when it starts interfering with licensed users).
It MAY be possible to use SDR to achieve LPI while still remaining within
if you're building LPI, you don't give a fuck about the FCC (compliance). by definition, if they've found you, you fucked up!
Perhaps, but I'm not about to suggest that anyone break the law.
Actually, that gives me an idea: MIMO precoding[2] (versus spatial
multiplexing, which is useless for your purposes). MIMO precoding devolves to beam-forming in the absence of reflectors like buildings, but in an urban environment, you get a complex combination of signal paths,
MIMO precoding requires a "training" phase where they discover one another by transmitting some easily "locked-onto" signal so that each receiver can find the other transmitter independently.
it is now possible for a professional's budget to accodomate the SDR equipment necessary to do this type of phase sync'ed active beam forming MIMO transmission, and not all methods require the training phase. in fact, omission of this (by out of band training, in a sense) in a method of "keying" phased delivery of UWB MIMO in a way more likely to achieve LPI.
How do you train out of band? By modelling the environment? That's an interesting thought, and I suspect Google Earth has enough data to be able to do it in a lot of places. Are you aware of free or inexpensive software packages for doing this?
synthetic aperature millimeter wave vision systems are also pushing along this boundary, for cross-pollination of suitable phased sync'ed UWB MIMO signal processing.
Aren't you just talking phased array for something like this though? Or do you mean using phase information from the receive antennas to reconstruct the environment rather than using phasing at the transmit side to steer your beam? That's a very interesting idea since it can give you a 360 degree view with no need to steer your beam, in the same way that some blind humans can use clicks to get a picture of their entire environment. (I use humans and not bats because I think bat sonar is pretty directional, whereas human ears can localize sound quite precisely without any need to turn one's head.)
i could go on, if you're curious, but perhaps on another list? :)
This is definitely an area I'm interested in, so I'd love to hear more of your ideas, as may Jeremy, so if it's beyond what is generally tolerated on this list, private email would be fine, or if you have a list in mind I'd be happy to subscribe if I'm not already.
participants (3)
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coderman -
jim bell -
Sean Lynch