31–38 of 38 posts
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> is probably going to use LoRa why not Zigbee or Thread?
I think most ZigBee and Thread chips use 2.4 GHz which limits distance. A lot of water meters are underground on the front yard somewhere so sub gigahertz radio would penetrate better. The modulation scheme of LoRa also allows for greater distance at the cost of data rate. It's also super low power.
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If you document this somewhere I'd love to read about it! I took the approach of sniffing the packets between the radio and mcu on the bridge board, got most of the way into reverse engineering that, then helped build this instead: https://github.com/tronikos/esphome-magnetometer-water-gas-m... But I always wanted to finish pulling flume data to home assistant, without the cloud.
I am planning a write up once I get it working. I'd be happy to share. My setup is a logic analyzer tap on the SPI bus between 8266 and the RFM69 on the bridge device to log raw traffic, and my secondary RX (ESP32 + RFM69) for over-the-air traffic. Also, I have a gas meter sensor based on your work half-built on my workbench. I plan to set that up once I finish my Flume distraction. Great work, thank you!
I'd done exactly the same, though my efforts were pre-Claude. If you want my logs/data, username at gmail.
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How did you get the epoxy off the ESP? I use a mill but I only have a 30% success rate.
No need — I simply plugged into the exposed programming header on the gateway. The sensor has an Atmel SAMD part which I assume has the security bit set. I didn't need to dump that firmware directly as it exists within the gateway flash.
So if I understand correctly, they used hard coded constants to generate keys that only have 44 bits of entropy, which is brute forcible for $10, but you have to do it per device. They presumably did this to make pairing the bridge and sensor easier while not using a static key for all devices. Not the worst compromise I guess. I've been working on an open source solution on and off for a number of years called http:…
Why not LoraWAN - has built in encryption (via preshared keys) and receiver stations + processing software already exists (Chirpstack).
One thing I appreciate about this kind of research is that it doesn't assume every wireless protocol must end with a catastrophic vulnerability. A result of "the security is actually pretty good" is arguably just as valuable as finding a critical flaw. It helps distinguish between systems that are merely proprietary and those that were designed with a reasonable threat model in mind. I'd be interested to know where t…
> the security is actually pretty good I had a slightly different read.. their CTO replied directly and in an affirmative manner. It's amazing how the human touch helps align and build understanding. How many of these have you read where it's just a scathing product teardown devoid of any appreciation for any work that's otherwise been put in.
it is full-on broke on my phone, showing only pictures and no text
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44 bits of security is not “pretty good”. The post author used Python, but anything more performant would result almost real-time decryption. There are no performance implications of using a proper 128 key because they are doing AES anyway. If they were resource constrained and choose a variant of TEA encryption due to constraints, it would be understandable, but no, the encryption is implemented in hardware. There a…
Last I tried in my small city in Ohio, it seemed like all of the natural gas meters as well as all of municipal water meters were broadcasting their readings and messages in-the-clear for anyone within RF earshot to decode as long as they had an inexpensive SDR dongle and a copy of (IIRC) rtl_433. It was summertime and the gas meters were boring, but the water meters were pretty chatty. 44 bits is a lot more than 0.
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No need — I simply plugged into the exposed programming header on the gateway. The sensor has an Atmel SAMD part which I assume has the security bit set. I didn't need to dump that firmware directly as it exists within the gateway flash.
The gateway had an open debug port?!?!