-------- Original Message -------- From: Sean Lynch <[email protected]> Apparently from: [email protected] To: [email protected] Cc: [email protected] Subject: Re: [tor-talk] Using SDR Date: Sat, 06 Feb 2016 20:40:21 +0000
> On Fri, Feb 5, 2016 at 7:23 PM coderman <[email protected]> wrote: > > > > On 2/5/16, Sean Lynch <[email protected]> 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. > > Alternatively, if you aren't too clumbsy or forgetful, is to have a some sort > of hidden/innocuous band tied to you and to your device (e.g., a laptop) that > when pulled too hard (like a grenade pin) starts the wiping process. So if > you are jumped/pinned the process starts before the attackers realize it. > > > > > > 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! > > > > +1 > > > > > 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. > > > > A related LPI method is to use a separate, well disciplined, carrier > > (in-band, co-located or not) that participant devices listen to and use > > the sync their clocks and/or their codes. If used carefully Eve won't know > > about it and will find it too difficult to synch in time catch Alice and > > Bob's comms. > > > > > 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.) > > Beam stearing be accomplished much cheaper than via a phased array using > nearfield plasmas to block or steer the beam. For example, a vertical cluster > of flourescent tubes surrounding a simple dipole can, with proper circuitry, > quickly switched so that only one of the tubes is "off" (transparent) at a > time allowing incoming/outgoing signasl to only propagate in that direction. > The other tubes are "on" and reflect the signals. > > > > > 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. > > -- tor-talk mailing list - [email protected] To unsubscribe or change other settings go to https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-talk
