-------- Original Message -------- From: Sean Lynch <[email protected]> To: [email protected] Cc: [email protected], [email protected] Subject: Re: [tor-talk] Using SDR Date: Mon, 08 Feb 2016 20:16:58 +0000
> On Mon, Feb 8, 2016 at 10:51 AM <[email protected]> wrote: > > > > > > -------- 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. > > > > > > > > > > > Yep, a dead-man switch of some kind is a good idea regardless of what other > techniques you're using. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > 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. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Sure, but if you have a very long (or effectively infinite) PN sequence, your > carrier needs to be structured enough to recover some large counter. GPS > qualifies, as probably does WWV and its non-US brethren. > > > > > > > > > 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. > > > > > > > > > > > Sure, if you don't care about MIMO, there are lots of ways to steer your beam > using relatively cheap circuitry. You can have multiple transmit/receive > antennas and just adjust their relative phase. AIUI this is how the LoJack > locators operate. Switching reflectors on and off independently as you > suggest here would allow multiple beams, though their relative phase would > not be adjustable. It all goes toward the goal of minimizing the amount of > energy you emit that isn't directed toward the receiver, though. > > For privacy in ptp links and a highly directional antenna (e.g., a parabolic > dish) one can take a cue from covert radar tech. Alice geometrically moves > around the transmit signal, and thus far-field phase, using a "matrixed" > near-field feed that switches randomly at >> than the symbol rate. If you can > adequately suppress the switching noise the phase shifts make it near > impossible for an off-axis (> 0.5 degrees for a 32-element 2D feed) Eve to > even detect that a signal exists. Bob, all other things being equal, using a > standard receiver, should have no problem with receiving. This tech is > practiced only at the antenna and, like Orbital Angular Momentum, should work > with near any emission type or protocol without need modify other equipment. > > Thanks for posting the latest version of your slides. I read what I think was > an earlier version previously. I am working on upgrading my amateur radio > license, so soon I will get some experience with some of the weak signal > modes you talk about. > > -- tor-talk mailing list - [email protected] To unsubscribe or change other settings go to https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-talk
