Reverse engineering my Coway air purifier to ditch the cloud

> The fan downloads its root CA cert over plain HTTP. It was always MitM-able.

The most fascinating part of this wave of LLM reverse engineering is seeing how many weird and poor choices were lying in plain sight.

Any number of people could have discovered and exploited this, but it’s tedious work. Most people who can do this are busy with their job and other things. Now LLMs enable people who understand these things to quickly get through the tedious parts, so they can do a lot more of this work in their free time than they could before.

This works better than all of the hepa purifiers on the market:

  1 20" box fan.
  4 20" mirv 13 filters (cheapest is likely costco or lowes or home depot - buy in a 4 pack to save money).

This is still expensive but the amount of air processing per hour is incredible.

More info Search "Corsi-Rosenthal Box" or click https://filterbuy.com/resources/air-filter-basics/how-to-bui...

Don't go hepa because it slows down the filtering too much. I use this technique in my house and it cuts down on pollen, smoke and mold. You'll feel a lot better than a tiny expensive hepa that has proprietary filters.

I just liberated my Haier AC units. The WIFI modules it came with but that I never used turned out to be ESP32's, with solder pads for rx/tx etc. I soldered on some wires, plugged into a USB ot UART dongle and Claude had ESPHome running in no time. I now can not only control the AC units, but I have a lot more visibility into wat it is doing: coil temps, gas temp, valve positions: all is available and all is logged now. I also liberated my air purifier long ago by soldering a wire to the various buttons, so i can trigger a press the physical buttons from an esp32. And I soldered a wire to the PWM of the fan, so I can bypass whatever the onboard logic is doing. Liberating your own electronics is fun, and now with AI easier than ever. I also ditched the WIFI unit of my solar inverter and hooked up the tiniest ESP32 nanoC6 and now I get all the data at 1Hz. Still working on taking over the EcoFlow batteries and their charging/unloading logic.

This also means that we have a short window where products d hardware can be reclaimed by users. After a while, these makers will also start using LLMs to lock the devices properly.

I took a Vornado TRANSOM, a Broadlink RM4, and a Shelly Smart Plug, a Qingping Air Quality Monitor Gen 2 + claude and HASS, and now I have a fan that turns itself on when the CO2 level gets too high.

And I can override or change it from Apple Home.

The smart plug lets it verify that the fan is actually running, (because it measures usage) and we worked out that after a power cycle the Vornado goes back to a known state, and we can find the speed by forcing it all the way to 4 and then stepping back.

It is great to see another cloud mandatory device set free. I noticed lately several such entries in HN and personally it is a good trend.

I am wondering how the big corporate will respond sooner or later. Because it is clear and they know that as well with the every rising capability of LLM more people will find ways to liberate their hardware from such unnecessary dependency and accept less the money drain.

Jeez. I've had a Coway for about eight years, such a good device that my whole perception was “good product == good company”. If I had known their IOT offering was such a POS I would think very differently.

That said, the non-wifi model works perfectly with a simple HomeKit compatible on/off plug, so all this work — despite being very, very cool — seems a little pointless?

Your central HVAC system is by far the best way to keep the air in your house clean. You can run the blower without heat/cool 24/7 without spending too much money. Most modern furnaces have variable speed ECM fan programs that slow down when no heating or cooling demand is present.

You can't install a true HEPA filter directly in a typical residential system, but you can have an HVAC tech install a bypass system in the air handler that would allow part of the air stream to be filtered via HEPA continuously. If you build the system (or house) from scratch and express your intentions to the HVAC contractor you could plausibly use direct HEPA filtration for 100% of airflow.

https://www.lennoxpros.com/healthy-climate-hepa-60-bypass-ai...

I misread this headline and now I want a Cowsay air purifier.

I have 2 Coway air purifiers, they have no cloud stuff. They work really well.

While this is impressive: Why not just get a not-cloud one in the first place? Why does an air purifier need to be controlled via wi-fi?

I'm against a lot of smart home things because its actually more maintenance, not less, to have to think about an object connecting to wifi, to have to decide whether or not to control it (what are you even doing to it?) And I suppose to have to write your own drivers or app. Why allow it to occupy this much mental space for you?

I’m quite happy with my MedifyAir MA-125. Just mentioning it and the brand since I don’t see it often mentioned. I’ve had mine running for around 4 years continuously at this point. It feels good quality too and marked/sold as commercial, and since it’s quite large with a large fan, it’s quiet.

I wanted to do the same with Phillips air purifier that uses AWS IoT. Unfortunately, it seems the engineers did their job: an eMudhra-signed certificate was not accepted and the AWS endpoint also uses mTLS, so I wasn't able to MITM the connection.

Their ESP also uses Secure Boot... I don't know that there isn't a way to break in, but I wasn't able to find one short of hardware notification :/

I love how it has become a trend now to take some device that required a cloud subscription, reverse engineer it, then connect it to your own server you control.

Suddenly there are so many products to play with that would have previously been undesirable! This is one of the good things AI has enabled.

For anyone considering getting an air purifier, please do not get a Coway (or similar brands).

The air purifier market is full of garbage because consumers don't understand how these products work or what their tradeoffs are.

The root problem is that these products are designed the wrong way around. They almost all use custom-fit HEPA filters. That sounds great, HEPA is good, right? Except HEPA is really not good for household air filtering. HEPA is so fine that even air struggles to move through it. It's also far more fine than the common contaminants (dust and pollen) need. Because it's so fine, you need a VERY powerful fan to move any air through it, which means the purifier will be very loud.

Finer filters are not better. There are two things you want to optimize for:

1: CADR - clean air delivery rate. This is essentially how much air you can move through the filter per hour, multiplied by how much of the contaminant you can catch each time that air passes through the filter.

2: Volume - It doesn't matter how amazing your air purifier is if it sounds like a tornado. If you only run it for a few minutes before getting annoyed, the purifier is not doing its job. Every moment it is OFF it is not doing its job. Many purifiers try to use sensors to determine when to run the filter, but this fundamentally a flawed approach and just means you have low quality air 99% of the time.

The solution to these problem is a less-fine filter. For dust and pollen, something like MERV13/14 is absolutely fine. It will catch most of those on each pass, and because air moves through it so much easier - you can run the same air through it many times more in the same period of time. This results in an air purifier that is whisper quiet, keeps the air far cleaner, and can use off-the-shelf furnace air filters that are VERY cheap compared to custom-fit HEPAs which may stop being made the moment that purifier product line inevitably ceases to exist. (Note: This is mainly true in the US, said filters are harder to find elsewhere)

Combine MERV13/14 with off-the-shelf PC case fans (which have been optimized for decades to be as quiet and long-lasting as possible) and the result is an easily-maintainable, quiet, highly-effective purifier.

NOTE: People dealing with VOCs/odors need an entirely different approach that HEPA won't really solve either, for that you need activated charcoal which will run out almost instantly in the amounts common purifiers come with. You need a gigantic block of the stuff to last more than a month or two.

Has anyone managed to pull this off with the Levoit air purifiers. I've isolated mine on a seperate VLAN at home but it requires internet connection to control.

Corsi-Rosenthal box is way cheaper and only connects to the 60hz.

I'm guessing here that the Apple Home app and integration are all local, not using Apple's Home cloud?

I have a light with a controller on the cord: brightness up/down, power. I can't use a smart plug with it because it always defaults to off. Any ideas?

I can't express how happy stuff like this makes me.

its a bummer how gimped claude models have become for research like this

This one yeets in a CA insecurely but eMudhra has been a gift for any that bake the CA--especially the abandonware unlikely to ever get patched.

All that to control one of 3 fan speeds. An extra slap in the face when it seems the motor used (at least in a similar model) appears to be continuously variable.

https://github.com/device-teardowns/coway-ap1512hh

If a company "banned" me from my ability to use the product I bought, that product would move swiftly to a skip-fire.

Air purifiers need an Internet connection in case someone invents a new kind of air.[1]

[1] https://xkcd.com/3109/

On topic, can you recommend a good air purifier to run in the office? 500 sq ft?

I am tired of having dust everywhere.

i truly wish these things were not smart in the first place

We need an Orthodox Union for IOT devices. Parev Kosher would be unlocked bootloader. Meat Kosher would be open source firmware . One level could be an escrow service for skittish companies, where escrow shares the firmware when the company terminates support.

It works in many other industries like UL for electronics, Intertek, NSF for foods etc.

Anyone know how to permanently disable the ionizer feature on these fans? I hate that it has this feature which is hazardous to health.

ChatGPT will allow you to do this interactively then ban you a few days later. Good luck OP.

Will be interesting to see how things go in a few years when companies start rolling out devices where the software was built by LLMs

It will unfortunately be a lot harder to free those devices

We need a frontier to explore and exploit. Without it we turn inward, trying to chisel another 0.1% off each other.

I'm a simple man. I see people freeing their devices from proprietary clouds and reclaiming ownership, I upvote.

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Hy I am a backend engineer .I built Kafka and Redis alternative .which is fully 100x fast .Now is open source in GitHub