hey wanna read some horrors? https://www.w3.org/TR/exi/
Efficient XML Interchange (EXI) Format 1.0 (Second Edition)

@whitequark
The real horror is that #EXI is used in an ISO 15118 sandwich on top of HomePlug AV (with broken encryption) and TCP (mostly with no encryption, but sometimes mixed with a wild PKI) to real-time control up to a Megawatt of electric power flowing into a car.

#PowerLine #V2G #EV

@ge0rg aaahhhh

@whitequark
And to add to the horror, all of the cars and chargers are in the same physical powerline broadcast domain, so when another car is plugged in, it needs to broadcast ping and measure the response signal strength(*) to find out which charger it's connected to...

And once the data channel is up, you authorize the payment with the absolutely unforgeable and secret... *checks notes* serial number of your RFID card!

(*) SLAC (Signal Level Attenuation Characterization)

@ge0rg @whitequark I'm sorry, THEY'RE IN THE SAME BROADCAST DOMAIN AND THEY DO WHAT???

@robot
You know, powerline is essentially a high frequency radio protocol using power lines as antennas, and there is _quite_ a bunch of power lines in an EV charging park.

https://www.sstic.org/media/SSTIC2019/SSTIC-actes/v2g_injector_playing_with_electric_cars_and_chargi/SSTIC2019-Article-v2g_injector_playing_with_electric_cars_and_charging_stations_via_powerline-dudek.pdf §3.2 has a nice write-up of that protocol. Bring booze.
@whitequark

@ge0rg @whitequark i just assumed there was some attempt at isolation, thanks for the article. I definitely am going to read it.
@robot
The isolation happens by creating a logical powerline network between the EV and its charger, after the attenuation measurement, by exchanging the network encryption key in cleartext.
@whitequark
@ge0rg @robot @whitequark you're kidding.
@robot @ge0rg @whitequark no. i refuse to believe it. there is no way the people designing critical EV charging/V2G systems are this catastrophically bad at their jobs
@AVincentInSpace @ge0rg @whitequark they didn't design the powerline communication standard. watch the talk posted elsewhere in the thread or read the (different but related) pdf