Hacker Cuts Coway Air Purifier Off the Cloud Using a Broken Certificate Authority
Reverse Engineering My Coway Air Purifier to Ditch the Cloud
Tired of Coway's flaky cloud service banning his account and breaking his Home Assistant integration, a homeowner reverse-engineers the Airmega IconS purifier to control it locally. The trick: a 2026 eMudhra certificate authority flaw handed everyone a working root CA, letting an LLM-configured Raspberry Pi man-in-the-middle intercept the fan's traffic and reveal how it talks to Coway's servers.
For the next few days or weeks, anyone now has a root CA thanks to eMudhra. Time to have some fun with MiTMing unwilling devices!
- Aurornis
> 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.
- throwitaway222
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.
- tda
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.
- bob1029
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...
- Eric_WVGG
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?
- bombcar
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.
- radicality
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.
- eande
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.