[Dominic Buchstaller] wanted a neat, tidy entryway keypad that actually looked good. Prime goals were something slim, wireless, and with no visible screws. Dependency on the cloud was also a no-go. With few ready-to-go options available on the market, he set about whipping up his own.
The heart of the build is an ESP32-C6 microcontroller devboard. This device has the benefit of including Zigbee communication functionality baked right into the chip. It’s hooked up to an MPR121 capacitive touch controller, which allows different segments of the touchpad PCB to act as capacitive buttons for numerical entry. The number labels are directly printed on the PCB solder mask, so there’s no overlay or other label required on top. Power is courtesy of a 1300 mAh lithium-polymer cell which gives a useful lifespan of six months between recharges. A simple 3D-printed case holds everything together and completes the clean and simple look. [Dominic] notes that it’s possible to also use the device via Matter or Thread without a lot of changes, as the ESP32-C6 can easily handle those protocols, too.
If you’re looking for a cheap, handsome keypad for your Home Assistant setup or similar, you might find this useful. We’ve explored DIY keypad entry systems before, too. If you’ve come up with some other creative way to get into your house, car, or bank vault, be sure to notify us via the tipsline.
Unless a rotating encryption system is used this will be highly vulnerable to a replay attack.
Not really, both Zigbee and Matter establish cryptographic sessions before being able to exchange information. Matter has more advanced security over Zigbee. Thread secures the 802.15.4 layer with its own counters, and Matter adds an application-layer message counter plus a reception-state window (IPsec-style anti-replay). More importantly, Matter traffic runs inside CASE sessions keyed with ephemeral session keys that rotate and expire. A frame captured in one session can’t be replayed into a new one, so the replay window is bounded by session lifetime rather than being open indefinitely like a static Zigbee network key.
https://docs.silabs.com/matter/2.2.0/matter-fundamentals-security/
But 2FA is always better, so you could add smartphone bluetooth device detection as an extra factor; and have a backup plan if the electronics fail ;)
What he said …
It’s just a keypad, so why would a replay attack matter?
correct, it does not matter!
or, it does not zigbee, whichever you prefer 🥳
I’ve been looking to make something conceptually similar, but I went for an nrf52. In theory the battery endurance is massively better; anyone else had experience of this?
Well you can … but the battery life is ridiculously long as it is (more than half a year) and won’t be any less with other chips as the main current draw is contributed by the touch controller in standby
Any more*