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Comment by kanobo | Hacker News Reader

Tomorrow's news: Privacy Lightbulbs that vibrate pre-recorded messages to throw these pesky spies off their trail is invented.

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Whilst the suggestion is clearly not serious, having pre-recorded or even repeated random noise is akin to re-using a one time pad. Continued ‘listening’ - even long after the relevant conversation - could first be used to extract the fake noise and then from this the signal.

I'm going to put on my pop-science-fiction hat on and revise the Privacy Bulb to include a geiger–müller vibrating tube and a dollop of uranium for random vibrations. I was a fan of spy vs. spy as a child and I am full of bad ideas right now.

Yeah. You can't just produce random white sound[1] to cover the signal either, because speech has enough redundancy to still communicate over a static-y soundscape. The term here is that white noise lacks "diffusion"--analogous to the ECB vulnerability (see the picture of the encrypted Linux penguin image on this page[2]). I can't think of a good way to provide diffusion for sound--a better cover might be to provide alternate signals, i.e. a few layers of random human sounds spoken in a deepfake-d version of the voice of the person speaking.

I'm skeptical even this wouldn't have vulnerabilities however, as history has shown us that cryptography which has not been formally proven is often broken.

[1] I'm using the word "sound" here to differentiate the noise in the auditory sense from noise in the "signal versus noise" sense.

[2] https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation...

Would it be possible to use the tech in noise-cancelling headphones and put a tiny speaker that phase-cancels audio it hears to solve this issue? I'm asking as someone who knows very little about this.

Well, it's definitely possible to do that but I'll make no claim that it would actually provide security. There's definitely some bleed-through with noise canceling (i.e. the beginning of sounds don't get canceled because the noise-canceling has a "reaction time"). It's probably better than nothing, but I would guess that a sophisticated-enough attacker could get around it.

Again, I have no proof of concept here, so take with a grain of salt.

Then you can hijack the noise canceling device and obtain the original signal. Also the canceling effect is likely never perfect, so there would still remain part of it going through.

What if you use one random source to contentiously change the white noise parameters (mean, std).

E.g. use something like a illuminated disco ball that continuously randomly changes the source light angle and intensity.

I think it would be very difficult to escape from diffusion problems.

Since you mention it, I got to thinking about whether we can have a microphone equivalent to the physical covers for webcams -- that is, a physical means that ensures the device can't detect anything usable, even if an attacker was able to turn it on without you knowing.

Something like, a vibrating module that you don't really notice but which clouds out any sounds the microphone would pick up (or, to go your route, injects fake audio). You turn it on when you want to be sure the microphone isn't listening, just like you can cover the webcam.

Some offices employ white noise privacy machines, you can find them on amazon. And the Japanese have the Sound Princess for flush noise privacy at the toilet. I have yet to find a product where you don't notice that it's on though, would be a great invention if possible.

Or you could turn on the shower and faucets in the bathroom and talk there. Or does that only work in the movies?

It does work, but you can have filters that can remove that noise electronically enough to get some actual voice signal. Faucets along with whispering directly in the ear would work. But a better choice is to simply write on a piece of paper instead of talking.

You mean something like this [0]? You could use this to trick your computer/phone into using the audio jack for its microphone, but since the mic-lock passes no usable signal, you'll be better protected. It doesn't otherwise incapacitate the internal microphone, though.

[0] https://www.amazon.com/Mic-Lock-Microphone-Blocker-Pack-Surv...

It would need to block the microphone itself that picks up ambient noise -- I don't think there's anything on e.g. a MacBook Air that you could plug that into and block sound.

We've known each other, for so long...

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