[keyme]

As long as the modem is connected via SDIO/USB to your open system (which it is), how is this a problem? It's treated as compromised/hostile.

Encryption of IP traffic happens on the open system, so no problem there.

If you'd like to complain about encryption of voice calls happening on the closed modem, I have some bad news. It wouldn't matter if it was open or closed, since the network it negotiates keys with is also compromised.

The only problem remaining, on this particular device, is direct connection of physical sensors (microphone, GPS, etc) directly to the modem. This is solved by physical switches (or hardware switches controlled from the open system) between the sensor and the modem.

The only exception I see now is the GPS, which is embedded into the modem. If they solve that, I'm buying the phone.

[npo9]

You gave a great answer to my question. Thank you.

[mirimir]

Right. There are two distinguishable risks from cellular or WiFi modems. One is geolocation by towers or access points. And the other is isolation of the open system from cellular or WiFi modems.

You can't use cellular or WiFi without being geolocated. But as long as the modems are securely isolated from the open system, geolocation information can't pollute your communications. There's obviously the same geolocation issue with broadband.

Also, that isolation prevents compromised modems from compromising the open system, and the accessing data, compromising end-to-end encryption, and so on.

Both are aspects of modems being "treated as compromised/hostile".

[dev-il]

> The only problem remaining, on this particular device, is direct connection of physical sensors (microphone, GPS, etc) directly to the modem

is that even the case of the microphone? My understanding was that - independently of the possibility to turn the microphone and modem off with kill switches - all audio data to the modem comes via I2S from the SoC anyways, i.e. that the microphone is NOT directly connected to the modem but to the SoC (possibly via a separate audio codec Chip) and that the SoC serves the modem via I2S whatever audio data the user pleases (whether that be from the microphone or whatever else).

[MartijnBraam]

Yes, the modem can't talk to anything, it's only connected to the SoC with the i2s audio bus and the usb bus, the SoC controls what gets sent to the modem. for a voice call the SoC proxies audio between the mic/speaker and the modem.