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Saturday, November 9, 2019

Microphones with tattle lights and passive wearables

Sometimes, I look at the confluence of technology and culture and wonder where it will take us. I see problems which could crop up, and solutions which might be demanded by an enraged public. Think of when that one iOS app scarfed down everyone's address books, and that started the whole thing of finer-grained permissions and pop-ups instead of them "just having access".

This particular half-baked idea comes from considering the situation with these "home assistant" (HomePod, Alexa, whatvever) boxes that are sitting around listening for trigger words. Since this always happens in software, it's not much of a stretch to imagine it being co-opted to do evil.

It's not enough to just have a "tattle" LED in-line with the mic hardware, though, since it might come and go too quickly for you to see. No, this particular wacky idea involves a lot more subtlety and nuance.

Imagine if there was a bit of hardware wired up to the mic, such that when energized by the host system, it had to "charge up" before the mic was connected to the input lines. While it was "charging", some kind of light might appear, or it might play a sound (through a local squeaker thing, not the main software-controlled speaker), or both. Then, once it got up to the right level, the mic would be switched into the circuit, and it would indicate this for anyone who happened to be watching.

At some point, the device would decide it was done listening, and would de-assert the audio input. The hardware would then "discharge" in such a way that a different "tattle" LED stayed on for some number of seconds. This way, you'd know that this thing had been on and had been listening to you at some point in recent history. The whole point is to thwart attempts to "pulse" the sensor to spy on a room without lighting up the LED (as you could probably otherwise do).

So naturally, this is where people start going "but if the mic is off until the software triggers it, how do you trigger the device remotely", and they'd be right. "Hey Siri" can't work if there's no mic. For that, I propose something even less-baked (quarter-baked idea?) which involves some fun and games with RF energy.

There are passive devices which behave a certain way and resonate in the presence of a RF field. They're used for anti-theft applications. Start with that. Then recall the whole iPhone 4 "antennagate" thing, where us silly meatbags kept holding the device and bridged the antennas (in the outer metal band) in weird ways and screwed up the signal. Now recall that everyone using one of these home assistant devices is likely to have at least one 2.4 and/or 5 GHz transmitter for their wifi networks.

Glue all of that together, and you might just be able to create a totally passive "wearable" that behaves one way normally and behaves another way when touched or bridged by a tap, or a squeeze. It wouldn't have a battery and wouldn't do anything beyond a certain range, but it would be fine for triggering stuff around the house.

Are there giant problems to be solved here? Of course. Do I think it'll happen? I do. I think eventually, someone will put all of this together. Maybe there'll be some kind of "mic standard" where manufacturers commit to only wiring their microphones up through this kind of tattle device, and then enterprising YouTubers can tear them down and verify its behavior to keep them honest.

If this happens, cut me in on the action, ok?