On Mon, Feb 8, 2016 at 10:51 AM <wirelesswarrior@safe-mail.net> wrote:

-------- Original Message --------
From: Sean Lynch <seanl@literati.org>
Apparently from: cypherpunks-bounces@cpunks.org
To: tor-talk@lists.torproject.org
Cc: cypherpunks@cpunks.org
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 <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.

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.