[idontwantthis]

> Because mmWave radar doesn’t process visual light, what it sees is not personally identifiable. This makes it an ideal choice for monitoring where a camera would not be appropriate.

Is 5mm resolution not enough to identify a face?

What’s the difference between a 3d model of a person constructed from high res radar and a black and white photo?

The radar sounds even more identifiable.

Edit: Couldn’t you construct a mosaic and have much higher resolution?

And also remove their clothes?

[krasin]

I worked with mmWave radars previously, but not professionally. In my opinion, it would be quite challenging to extract enough features from the current generation of mmWave radars, such as TI IWR1642 ([1]) which have around 4 receivers and 2-3 transmitters, because the incoming data, while having a lot of temporal resolution is very limited in spatial resolution.

With greater number of antennas something like what you describe is theoretically possible, but becomes cost prohibitive.

By limiting the number of transmitters / receivers, we can have an almost perfect privacy monitoring. For example, it would be possible to detect a attack / a fight in a public bathroom, while not exposing anyone.

1. https://www.mouser.ec/datasheet/2/405/1/swru521c-1954464.pdf

[jcims]

To an extent, but depending on the sampling rate and frequency and your ability to control the area being observed, there is still a lot of information available for modeling and biometric identification. In the extreme you can detect things like heartbeat, rate of breathing, etc.

For example, I have a CDM324 24Ghz radar module here on my desk. I set it up to 'watch' me type this comment from across the keyboard. This is an extremely simple module that I have powered by a bench power supply and the IF routed directly to the audio input on my desktop. It was sampled with audacity and amplified a bit to help with visibility. Towards the end of the recording I'm expecting a flat spot followed by regular motion followed by 'noise' as I pause motionless for ~10 seconds or so, then take about 5-6 exaggerated breaths, then resume typing.

This is with zero design, the wrong frequency for the job, and next to zero signal conditioning.

(post: i've included a zoomed in image of the 'motion demonstration' to show still/breathing/typing, then zoomed in on typing to show the detail, then a spectrogram and waveform of me reaching up to scratch my ear.)

https://imgur.com/a/0JmENYu

Bonus: yo check out my soundcloud - This is what the doppler signal actually sounds like:

Scratching my ear - https://soundcloud.com/buckrunner2/scratch

Talking directly at the module - https://soundcloud.com/buckrunner2/talking

[AdamH12113]

“Privacy” seems to be a marketing term here; what they really mean is that you can’t take naked pictures with it.

[samatman]

Which is also nonsense of course, the pornotron of TSA fame is mm wave radar.

[krasin]

The difference is the number of transmitters / receivers. TSA uses an array of them (from top to bottom) with narrow beams and they also rotate them and ask you to not move, so that effectively their number is considerably higher (ten of thousands), when reconstructing the image. Additionally, they use a higher frequency (160-400GHz), which additionally helps with resolution. See [1] and [2].

If we limit the number of transmitters / receivers to 3/4, the image reconstruction becomes impossible, similar how you would not really make a real photo from a few color sensors stationary looking at a scene, while a linear array of them that moves around an object would make a perfect scanner. It's a non-ideal analogy, but the best I can offer.

1. http://mt-fedfiles.blogspot.com/p/tsa-frequency-updates.html

2. https://www.3dbodyscanning.org/cap/papers/2017/17263mcmakin....

[visarga]

You can reconstruct the images with neural networks even if you have little signal to guide.

[samatman]

Sorry, don't buy it.

Gait analysis is excellent at identifying people, and that's projecting from a 2D image at a distance.

Anything which can draw a moving voxel cloud around a human is going to figure out who that human is eventually.

[kjeetgill]

I don't disagree but I think this version of privacy is reductive.

Plenty of real world privacy exists on a spectrum. My family knowing I'm in the bathroom is a far cry form them pointing a camera at me.

If stores track you "anonymously" with this ... Who cares? It's less invasive than the ubiquitous security cameras they have pointed at you.

[kortilla]

Google knowing every time I’m in the bathroom and keeping a detailed log of the times is a far cry from someone in my family happening to notice I go in there once.

[samatman]

I have no opinion on your reply, I was discussing technical feasibility in response to someone claiming it was infeasible. The normative claims aren't germane or particularly interesting to me.

[krasin]

By not exposing anyone I meant reconstructing an image. Identification is a different story and there are multiple ways on how to achieve that (heartbeat classification is an obvious one).

If you have ideas how to reconstruct an image with 4 receivers / 2-3 transmitters, please, buy a dev kit from TI (they cost <$200, https://www.mouser.com/c/?q=mmwave) and show us a demo.

[hornej]

I have a lot of experience with TI's IWR6843AOP chip and dev kit. It has 3 transmitters and 4 receivers and it'd be impossible to create a facial reconstruction with it.

[ulrikrasmussen]

What about correlation? If you have other information that can tell you who is alone in the bathroom (common area CCTV, log of RFID key usage, etc) and your radar can infer that something very private is taking place there because the person thinks they are alone, then isn't that still a huge breach of privacy?

[krasin]

I really must have phrased my message more clearly. I meant reconstructing images, not identifying who is inside. The latter is quite feasible, and you're correct that extra data helps with that as well.

Just like with browser pinning, we have a variety of signals, which combined together give a very high rate of correct identification.

[ulrikrasmussen]

Got it, I think I read your message as defending the idea more than it was.

[yjftsjthsd-h]

...so what I'm hearing is "hard today so probably trivial in 5 years"? Or is this an exception to the usual march of technological progress?

[R0b0t1]

Temporal res can be turned into spatial res.

[krasin]

Theoretically: yes. Practically, there are limits to that.

[hornej]

A couple examples to show what the mmWave data looks (bathroom, living room, etc)

Intelligent fall detection using TI mmWave radar sensors https://www.youtube.com/watch?v=lsIo_HIk4GY&t=93s

3D Occupancy Sensing For Home and Office https://www.youtube.com/watch?v=9EDhJQbLNyo&t=83s

As you can see the radar doesn't reveal too much, while still being able to discern a lot of what is going on in each scene.

[chrismorgan]

The visual signal there is utterly meaningless for assessing how much is exposed.

For analogy, take https://en.wikipedia.org/wiki/RANDU: it was very popular in its day, and its distribution looked good to the naked eye, but plot it in more than two dimensions and you see that it’s actually extremely terrible, failing spectral tests badly.

The information has been captured; the fact that one visualisation of it doesn’t expose that information is irrelevant and gravely misleading (as in: I don’t want someone that hasn’t already realised this working on this kind of stuff, because they’re dangerously ignorant and/or naive; I would rather they stop, and go and learn about the risks in detail before continuing).

[Schroedingersat]

> As you can see the radar doesn't reveal too much, while still being able to discern a lot of what is going on in each scene.

No, you can't see that, because it's a video of a specific visualisation of the data from one specific sensor.

If it can see through walls and measure biometrics like heart rate, mass and body type, build a 3d point cloud of limb positions and measure vibration, then it's more privacy invasjve than a camera, not less.

[hornej]

all sensors/technology are invasive to a degree, but I would argue radar fairs well in usefulness and anonymity in comparison to other sensors.

if the data were leaked, would you rather have some of your vitals and point cloud data exposed, or a video of you taking a shower?

[zardo]

I'd rather neither. I've handled the latter by not installing a camera in the shower.

[wavesquid]

You don't need to identify a face; you can identify people by Gait. If you can resolve something as big as a leg you've got enough, as long as you have it over 10 seconds or so.

[astrange]

It's odd that people care so much about technology "identifying them" when they have cell phones in their pocket and license plates on their car. There's not much of your daily life left after that, but I suppose it makes them feel good to imagine they're important enough to be tracked.

[kortilla]

I opt into carrying a cell phone and it’s when I want. I don’t opt in to my neighbor’s Alexa tracking my comings and goings by scanning through my walls.

[astrange]

You can do that by sniffing wifi packets even if you can't decrypt them, I think?

Could be a good opportunity for home Faraday cages.

[kortilla]

I don’t emit WiFi packets nor do I carry a device that does.

[astrange]

The point is that total wifi traffic in your house is correlated with you being at home, because when you're out, you're not using the computer.

[yosamino]

There is nothing odd about it, and it has nothing to do with being "important enough to be tracked".

It has become almost impossible to participate in society, without every aspect of your life being recorded in some way.

My Bank sells my transaction data to third parties to track my credit history and sell advertizing - they do this without my consent, or rather if I disagree, they will not have me as a customer. I could switch banks but it's basically the same everywhere. All I wanted was a place to store and transfer money.

My phone company sells my location and call data the government and to marketing companies - they do this without my consent, or rather if I disagree, they will not have me as a customer. I could switch providers but it's the same everywhere. What I actually wanted was to be able to make phone calls and have data connectivity on the go.

My ISP sells which websites I visit to marketing companies - they do this without my consent, or rather if I disagree, they will not have me as a customer. I could switch ISPs but it's basically the same everywhere. All I wanted was to have data connectivity at my home.

My airline sells my flight data to the government. They do this without my consent. There is no alternative. I just wanted to visit some relatives.

The government tracks all my phone calls. They do this without my consent. There is no alternative. I just wanted to call my friends.

The government tracks where and when and whom I send emails. They do this without my consent. There is no alternative. I just needed to communicate for my business.

When I go out in public, my image is records by a multitude of cameras, by a multitude of actors. They do this without my consent. There is no alternative.

My licenceplates are scanned, depending on my locality, more or less regularily. What I wanted was to make going around a bit easier over longer distances. There is no alternative.

My medical records are ... well there's something called HIPAA, but the reason it has to exist in the first place is that some seedy actors are trying to get their grubby little hands on this most private information of mine. I do not consent to this. I am sick. There is no alternative to medical care.

I go out in public and depending on where I go, cameras are being equipped with all sorts of biometric detection capabilities. All I wanted to go out for a drink, suddenly I am in some database.

I go online to browse the internet. No further explaination needed.

All I wanted was to have wifi connectivity at home. Some asshole has crammed functionality into the standard for wireless connectivity, that makes it possble to track where my body is. There is no alternative.

And so on and so on and so on.

All of these things taken together create an information asymetry. One by one they aren't neccessarily that terrible, but by accumulating all this information - for which there is constant pressure by the more authoritarian elements of our societies - creates a digital me, that absolutely has an effect on my day to day life.

Easiest example is my credit score, I am sure one can think up reasons to justify it's existance. But the point is, that this device exists as an incarnation just for me - without my consent at all. It's not that I need to be very important to have a credit score. I just have one by default.

It does not make me feel "important" to be tracked. It makes me feel oppressed. It's the opposite of important. Being treated like this, decisions being made about me by some usually invisible faces, makes me feel like cattle. I am being treated as a good that can be sold, and from which value can be extracted, in other ways than the exchange for goods and services for money. I am the commodity itself. By default I am presumed guilty, and evidence is being collected against me, even if I will never violate any law of society.

My right to live as a free interdependent member of society are being violated by the people who think they can use me and the data they can glean about me for whatever their purpose is - and they do this without even considering my consent.

Information asymetry enables control. It's the anti-thesis to freedom.

It has nothing to do with feeling "important" and the choice you are implying people have is not a free choice. It's forced.

[transpute]

> All of these things taken together create an information asymetry. One by one they aren't neccessarily that terrible, but by accumulating all this information - for which there is constant pressure by the more authoritarian elements of our societies - creates a digital me, that absolutely has an effect on my day to day life.

Well said.

[cj]

(Genuinely curious) how do you know this?

[hornej]

There has been research done on gait recognition https://techxplore.com/news/2018-08-artificial-neural-networ...

mmWave can be used to identify unique traits http://www.cs.ox.ac.uk/files/10889/%5BDCOSS19%5DmID.pdf

[smegsicle]

i recall a comment by someone claiming to be working in an antarctic base- everyone working outside would be wearing the same suit, but you could subconsciously recognize who you were looking at, at great distances, simply by the gait.

walk without rhythm ...

[hornej]

we're about to enter worm territory. we can't walk like regular humans. https://www.youtube.com/watch?v=1YFrFSX4cNw

[squarefoot]

It doesn't even need a radar sensor. Everyone moves in a different way, so that extracting patterns from the phone accelerometer can help to identify a person. Two people carrying the phone in the same pocket or hand will produce very different patterns that can be analyzed to extract the different behavior. All it needs is one chance in which that pattern is successfully paired with the person's identity, and from that moment on all their activities can be identified.

[fy20]

In terms of an IoT device or phone sensor form factor, not yet, but in the future I expect it will be possible.

Airport body scanners use millimeter wave radar, and they use software to mask the image so it isn't personally identifiable. There are even passive versions that just use background radio waves in a compact form factor:

https://www.qinetiq.com/en/what-we-do/services-and-products/...

[pishpash]

Each time something comes up like this, I call for jammers. If someone wishes to exploit the shared physics of the environment, I'll have no qualms to do the same.

[transpute]

There's some research, but more funding is urgently needed, https://ans.unibs.it/assets/documents/COMCOM-ext-WONS_Prepri... (Dec 2021 paper)

> This work explores the possibility of countering CSI based localization with an active device that, instead of jamming signals to avoid that a malicious receiver exploits CSI information to locate a person, superimpose on frames a copy of the same frame signal whose goal is not destroying reception as in jamming, but only obfuscate the location-relevant information carried by the CSI. A prototype implementation and early results look promising;

[deadmutex]

tl;dr is that the technology is very very different than a phone camera. So it's not the same as an IR photo. E.g. Google Pixel 4 has a radar chip AND IR dot projector+camera for face unlock. Presumably, if you could do face identification with Pixel 4's radar sensor only they would not have needed the IR tech.

Disclaimer: Work at Google, but not on Pixel 4.