I'm investigating getting off the cell network permanently to avoid at least the constant triangulation of my position. I figured I'd look into getting a VoIP number and getting calls and texts over WiFi. I don't mind being unreachable when I'm not connected to a hotspot, so it's not a problem for me.
But before looking for a good VoIP provider, I decided to check if WiFi still worked in airplane mode. And indeed it works. But to my surprise, when I connected the WiFi, my cellphone provider's name also came right back up at the top right of the screen. In airplane mode? What the hell?
Long story short, after investigating a bit, I realized I had WiFi calling enabled. So I can in fact already get calls and texts without being on the cell network.
And I'm thinking, maybe that's good enough for privacy?
I mean I know SIMs leak information like ICCID / IMSI / IMEI so obviously they have no reason not to do that over WiFi also and that's not so hot.
But on the plus side, none of that information is linked to cell towers and location anymore - at least not precise location if I'm not on a VPN - the baseband processor is off and can't do whatever shady chit-chat it does with the SIM and the cell towers, and I can still use my normal phone numbers without having to change and tell a million people that I have new numbers if I go with VoIP.
Also, I don't store my contacts on my SIMs and I use a deGoogled Android. So I figure that limits how much adversarial software can exploit the SIMs to leak data.
So it seems to me that WiFi calling may be a good solution for me for better privacy without too many compromises.
Can you think of something I missed that I should know before using this feature?
If I'm understanding how 'WiFi Calling" works; it's still "identifying you" to the cell provider the same way; via your SIM. The only difference is they don't get an exact location because you're not using any cell towers typically.
I do suspect SIMs and eSIMs are still doing all the heavy cryptographic signing done on a typical phone network though...they're just not screaming your IMEI/IMSI all over open or even encrypted airwaves; nor is a WiFI signal triangulate-able typically due to it's short range.
It is basically a SIP (a widely used VoIP standard) inside of IPSec (a type of VPN, and also a common standard). The IPSec credentials are provided by your your SIM card and that makes it about as secure as cellular.
Actually; (basically) SIP over (basically) IPSec sounds pretty correct. Wish the dense technical manuals I read had explained it that way; makes a lot more sense to me as a Net Admin type of IT person.
I do remember reading that the protocol was basically encapsulated. Dunno about any encryption; probably there's not any at the IPSec level. I do know that the SIMs themselves probably contain certs that have some value; I just don't know if they handle any encryption or if they're just lightweight little numbers for authentication only.
There’s encryption and it is managed by the SIM.