7 ms·

Decoding radio pH capsules with rtl_433

81 points by AndrewDucker 5y ago

lights0123 5y ago
Also of note is rtl_433's -A flag, which does a very good job of detecting how a particular device encodes its data on the radio, often making it only necessary to determine its frequency and what each bit means: https://github.com/merbanan/rtl_433/wiki/digitech_xc0324.README https://github.com/merbanan/rtl_433/wiki/digitech_xc0324.REA...
- heywire 5y ago
  Thanks for this! I’ve been using rtl_433 for years and had no idea about this walkthrough :)
userbinator 5y ago
What Dolske noted was that he was able to get ahold of was a copy of the manual (since lost to link rot) The one on Medtronic's site is 404 for some reason, but you can find it elsewhere: https://www.manualslib.com/manual/1486012/Given-Imaging-Bravo.html https://www.manualslib.com/manual/1486012/Given-Imaging-Brav... As well as the calibration procedure and (warning: not for the squeamish) "installation instructions", it contains some interesting phrases, such as "Any damage to the pH sensor will require the delivery device to be discarded before use." and "Warning Do not advance the delivery device into the trachea or lungs. Advancing the delivery device into the trachea or lungs can cause possible injury to the patient."
- _Microft 5y ago
  Checking the Internet Archive if the 404-ed page or file had been archived in the past is usually also a good idea. (I had always skipped over "manualslib" links in the past because I thought they were one of those shitty sites that try to sell copies of manuals that were pirated from the manufacturer's pages. Good to know that I was wrong!)
  - extraduder_ire 5y ago
    I find "Resurrect Pages" browser extension very useful for this exact problem: https://addons.mozilla.org/en-US/firefox/addon/resurrect-pages/ https://addons.mozilla.org/en-US/firefox/addon/resurrect-pag... It has saved me countless headaches reading old documentation and blogposts. It's worth it for the dead links to Raymond Chen's Old New Thing alone.
sgt 5y ago
Silly question, but why would such a device send an encrypted signal in the first place? If the range is so short, isn't that sufficient security? It would be similar to blocking the view so that nobody reads your screen, because it may contain sensitive data. I doubt pH is that sensitive to anyone.
- AndrewDucker 5y ago
  Best to encrypt by default. Always encrypt, no matter what, and then you don't need to worry about someone deciding that you need to turn it on later.
- tyingq 5y ago
  Commercial reasons maybe, ensuring you have to buy the receiver from the capsule manufacturer. Edit: A bit of Googling suggests there's some pretty bad setups in the wireless medical device market. Like pacemakers where you can send commands TO the pacemaker, with no authentication, signing or encryption[1]. Oof. [1] https://www.fda.gov/medical-devices/safety-communications/cybersecurity-vulnerabilities-affecting-medtronic-implantable-cardiac-devices-programmers-and-home https://www.fda.gov/medical-devices/safety-communications/cy...

81 points by AndrewDucker 5y ago

Also of note is rtl_433's -A flag, which does a very good job of detecting how a particular device encodes its data on the radio, often making it only necessary to determine its frequency and what each bit means: https://github.com/merbanan/rtl_433/wiki/digitech_xc0324.README https://github.com/merbanan/rtl_433/wiki/digitech_xc0324.REA...

heywire 5y ago
Thanks for this! I’ve been using rtl_433 for years and had no idea about this walkthrough :)

userbinator 5y ago

What Dolske noted was that he was able to get ahold of was a copy of the manual (since lost to link rot) The one on Medtronic's site is 404 for some reason, but you can find it elsewhere: https://www.manualslib.com/manual/1486012/Given-Imaging-Bravo.html https://www.manualslib.com/manual/1486012/Given-Imaging-Brav... As well as the calibration procedure and (warning: not for the squeamish) "installation instructions", it contains some interesting phrases, such as "Any damage to the pH sensor will require the delivery device to be discarded before use." and "Warning Do not advance the delivery device into the trachea or lungs. Advancing the delivery device into the trachea or lungs can cause possible injury to the patient."

_Microft 5y ago
Checking the Internet Archive if the 404-ed page or file had been archived in the past is usually also a good idea. (I had always skipped over "manualslib" links in the past because I thought they were one of those shitty sites that try to sell copies of manuals that were pirated from the manufacturer's pages. Good to know that I was wrong!)
- extraduder_ire 5y ago
  I find "Resurrect Pages" browser extension very useful for this exact problem: https://addons.mozilla.org/en-US/firefox/addon/resurrect-pages/ https://addons.mozilla.org/en-US/firefox/addon/resurrect-pag... It has saved me countless headaches reading old documentation and blogposts. It's worth it for the dead links to Raymond Chen's Old New Thing alone.

sgt 5y ago

Silly question, but why would such a device send an encrypted signal in the first place? If the range is so short, isn't that sufficient security? It would be similar to blocking the view so that nobody reads your screen, because it may contain sensitive data. I doubt pH is that sensitive to anyone.

AndrewDucker 5y ago
Best to encrypt by default. Always encrypt, no matter what, and then you don't need to worry about someone deciding that you need to turn it on later.
tyingq 5y ago
Commercial reasons maybe, ensuring you have to buy the receiver from the capsule manufacturer. Edit: A bit of Googling suggests there's some pretty bad setups in the wireless medical device market. Like pacemakers where you can send commands TO the pacemaker, with no authentication, signing or encryption[1]. Oof. [1] https://www.fda.gov/medical-devices/safety-communications/cybersecurity-vulnerabilities-affecting-medtronic-implantable-cardiac-devices-programmers-and-home https://www.fda.gov/medical-devices/safety-communications/cy...