4 ms·

Unless they are doing some serious wizardry, cars don't know which tire is which. Telling the tires apart was never one of the goals of the TPMS standards. Th

Unless they are doing some serious wizardry, cars don't know which tire is which. Telling the tires apart was never one of the goals of the TPMS standards. The transponder in each tire just shouts out its serial number and pressure on 315mhz and then sleeps for a random amount of time. The car counts how many times it has heard the various serial numbers, and assumes the top four most frequently heard serial numbers are its own tires (as opposed to those on the car next to it). It is sort of stupidly easy to gather location data from TPMS sensors. If I ran a major criminal gang I'd track the cop cars this way. 315mhz is almost VHF, it goes a long way. One receiver per city block should do it. Covering your turf would be easy.

chillingeffect 5y ago
>gather location data from TPMS sensors. That's one of the revelations from Snowden files. Us govt does this!
- lern_too_spel 5y ago
  Source? I heard of this trick from Schneier, but I have not seen any documents saying the US government is using it. In my experience, 90% of the things people say were in Snowden's documents weren't, so I'm skeptical. https://www.schneier.com/blog/archives/2008/04/tracking_vehicl.html https://www.schneier.com/blog/archives/2008/04/tracking_vehi...
  - chillingeffect 5y ago
    it's been a while but check back in a few days. if i can find it again i'll post it here.
BenjiWiebe 5y ago
Ok, first off - a lot of cars do know which tire is which. Most do it by associating certain TPMS IDs with certain tires. This is what the technician is setting when he does a TPMS re-learn (or reset) after rotating your tires. Other vehicles actually know which is which without being told. I'm not sure exactly how this is done, but I'm guessing/vaguely recall hearing they do this by using multiple receivers. As for tracking from a distance - these sensors have very low output power, and a lot of their signal is blocked by the metal wheel. It can somewhat be done but you'll need more than one receiver per block if you want 100% coverage. Sources: worked as a tire shop technician for a while, messed around with SDR, read a lot online. Also: https://web.wpi.edu/Pubs/E-project/Available/E-project-091115-154458/unrestricted/MQP_piscitelli_arnold_2015.pdf https://web.wpi.edu/Pubs/E-project/Available/E-project-09111...

chillingeffect 5y ago

>gather location data from TPMS sensors. That's one of the revelations from Snowden files. Us govt does this!

lern_too_spel 5y ago
Source? I heard of this trick from Schneier, but I have not seen any documents saying the US government is using it. In my experience, 90% of the things people say were in Snowden's documents weren't, so I'm skeptical. https://www.schneier.com/blog/archives/2008/04/tracking_vehicl.html https://www.schneier.com/blog/archives/2008/04/tracking_vehi...
- chillingeffect 5y ago
  it's been a while but check back in a few days. if i can find it again i'll post it here.

BenjiWiebe 5y ago

Ok, first off - a lot of cars do know which tire is which. Most do it by associating certain TPMS IDs with certain tires. This is what the technician is setting when he does a TPMS re-learn (or reset) after rotating your tires. Other vehicles actually know which is which without being told. I'm not sure exactly how this is done, but I'm guessing/vaguely recall hearing they do this by using multiple receivers. As for tracking from a distance - these sensors have very low output power, and a lot of their signal is blocked by the metal wheel. It can somewhat be done but you'll need more than one receiver per block if you want 100% coverage. Sources: worked as a tire shop technician for a while, messed around with SDR, read a lot online. Also: https://web.wpi.edu/Pubs/E-project/Available/E-project-091115-154458/unrestricted/MQP_piscitelli_arnold_2015.pdf https://web.wpi.edu/Pubs/E-project/Available/E-project-09111...