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Is WiFi calling a decent alternative to VoIP? (lemmy.sdf.org)
submitted 3 weeks ago* (last edited 3 weeks ago) by [email protected] to c/[email protected]
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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?

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[–] [email protected] 28 points 3 weeks ago (1 children)

Maybe?

Afaik wifi calling works the same as VoLTE, which afaik is just VoIP, but handled by your mobile provider, and integrated into your normal mobile plan, so it works with your phone number.

When both ends of a call have the service, the call is entirely VoIP, which is how it achieves the much nicer audio quality for these calls.

If you just completely disable the mobile radios (set your phone not to use any kind of connection from the sim settings, while still enabling the sim) and use wifi exclusively, then it should work as if you just have VoIP service?

[–] [email protected] -3 points 3 weeks ago (1 children)

Well, I know it's all going through the internet anyway nowadays, so yeah it's technically always voice-over-IP even if I use the cell network. The only difference between normal calls and WiFi calls is how it connects to the internet really. I just don't want the extra baggage that comes with staying connected to the cell netowk method of getting on the internet.

And of course what I referred to when I said VoIP is pure VoIP providers that sell you a number and access to a SIP server, independent from your cellphone provider.

[–] [email protected] 13 points 3 weeks ago

so yeah it's technically always voice-over-IP even if I use the cell network.

It's not. GSM calls are definitely still a thing, and while VoLTE is becoming more and more common, it's not universal.

[–] [email protected] 14 points 3 weeks ago (1 children)

This VoIP vs cellular doesn't have sense. Cellular networks are only link layer. They stablish low level telecom techniques to be able to transport any data to a cellular mobile belonging to the cellular net. The main difference with other link layer aproaches like wifi, ethernet, bluetooth, etc. Is that terminals are linked to a net of base stations in order to keep the best connection to the net at all times from every posible place. In order to do that each base station needs to know which terminals (phone numbers) are in his vicinity and in which sector. This way the cellular network knows where to look for when searching for a given terminal.

VoIP is an application layer service. Which means you can use VoIP over link layers like bluetooth, wifi, ethernet, cellular network. There's no VoIP vs cellular network. Cellular network can carry VoIP data because cellular network can carry IP datagrams. All modern cellular network use VoIP as their way to carry the voice information over the net and to maintain connection.

Wifi calling vs VoIP also makes no sense. You can do VoIP on wifi. Wifi is a link layer it can carry any digital data encapsulated.

What I understand you are saying is using VoIP through Wifi instead of using VoIP over cellular network.

In order to help a bit more, this are some.VoIP services:

Discord. Linephone Skype. Mumble.

[–] danhab99 4 points 3 weeks ago (1 children)

First of all I just want to say that I completely agree with all of the technical things you talked about in his question but I think you kind of miss his question.

OP doesn't wanna be on SS7 (the thing that gives you your phone number), neither do I. I've just come to the conclusion that when it comes to infrastructure and paying for your goods SS7 is the only realistic option I have.

There is no distributed communication network anyone can just connect to. And the dream of leaving WiFi access points open for free (or for some kinda crypto-pay, e.g SkyNet) is just a dream, individuals have to invest in it and nobody wants to or take responsibility for it.

Here are some rules:

  1. Somebody* has to build the radios and computers that our phones connect to and has to build them all over the world (*doesn't have to be an individual, could be a company or government)
  2. You gotta pay to use it (whether it's with a billing account where they have your full name and house address, or crypto)
  3. It's gotta be the easiest option

If we can come with a solution that fits these rules we can do away with the SS7 cellular protocol and have a truly anonymous network.

[–] [email protected] 3 points 3 weeks ago

Yeah I would also want that but a radio network without sector and base station sectioning but it is unfeasible. Frequency spectrum is limited and scarce, sectoring is used in order to share the same frequencies between neighboring base stations. Thus a rough positioning is intrinsic on the system.

Completely anonymous radio link requires a unique radio " address " for each terminal. This is not possible because you need multiple base stations in order to cover big areas, thus you need multiple limited frequencies.

WiFi is a good example. It's concept is very similar to cellular networks but in small scale (well or it was designed for small scale). WiFi access points suppose they have a more or less clear frequency (from other WiFi stations), with that in consideration they can search for any device that responds for a given address.

But notice that in the modern days new WiFi standards have come up. This is because now we have tons of WiFi AP per building, per house, the freq band is limited too. Modern WiFi implementations are copying the cellular designs with OFDMA. They are starting to use sectoring and MIMO techniques in order to separate the WiFi coverage in sectors.

From a telecommunications point of view cellular networks are better and more efficient that legacy WiFi implementations.

The problem is that because of this some knowledge about the positioning of the terminal can be known. But so do it with modern WiFi.

Again the problem is not the technology but how we use it. Do we have laws that respect user privacy? Nowadays you can geolocate someone by their IP because most ISP nodes are gelocated in order to map network shortages.

Tracking does not depend on you after all. Any station to which you are connected knows you are near them and since most stations.know where they are they also rougly know where are you.

The problem resides in the way we protect our data. Should users be linked to terminals? Well always that you identify yourself from a terminal you are somehow telling that you ARE that terminal.

The problem here is trying to separate the user part from the rest. We must focus on techniques that allow a user to identify themselves in an a remote service without linking it to its real terminal. Tor does that in a way by separating layer by layer.

Is a complex deal. Just be aware of this issues and try to not be fooled by the WiFi VoIP is the new thing super mega privacy. Because when you think you are safe is when you get stabbed in the back.

[–] [email protected] 14 points 3 weeks ago (1 children)

i'd imagine your phone carrier still knows where you are when you use wifi calling... especially if that wifi's internet source is a wireline isp or a known wifi-based network or hotspot.

[–] [email protected] 3 points 3 weeks ago* (last edited 3 weeks ago) (1 children)

I was planning on using a VPN.

But anyway, even if I'm connected direct from a known fixed WiFi, it's still less precise than cell triangulation.

EDIT: actually I just did a test with the VPN, and WiFi calling totally bypasses it. Damn 🙁

[–] [email protected] 0 points 3 weeks ago (1 children)

What about WiFi triangulation?

[–] [email protected] -1 points 3 weeks ago* (last edited 3 weeks ago)

Triangulation needs to know where the signal comes from (angles), which mode's device doesn't have the capability of doing this. The most they can do is estimate by signal strength.

[–] [email protected] 10 points 3 weeks ago (1 children)

Using things like Signal and WhatsApp may reduce your footprint further.

I’ve used wifi calling from hotel rooms overseas as well as locations where mobile coverage is poor and it works fine. I suspect (not know) that the voice network provider knows pretty much where your location is though.

[–] [email protected] 12 points 3 weeks ago (2 children)

Using things like Signal and WhatsApp may reduce your footprint further.

I use Signal with most of my family and friends. The phone things is for random people or companies that need to call me, and the texts are mostly to get notification when I receive a parcel, or confirmations for appointments, that kind of things.

WhatsApp, being owned by Facebook, can fuck right off.

[–] [email protected] 2 points 3 weeks ago

Totally agree about WhatsApp as I no longer use it due FB shenanigans. A lot of people do though which is interesting as it so easy to move.

[–] [email protected] 1 points 3 weeks ago (1 children)

For texts with parcels etc I have an old phone in a drawer which forwards texts to my email. Doesn't leak anything because it does not move.

[–] [email protected] 1 points 3 weeks ago (1 children)

What software do you use to forward the texts automatically?

Actually I kind of had the same idea but for the whole phone - i.e. leave a cellphone with phone features at home (so voice and texts are received on this static phone that never gets used for anything else) and forward calls and texts on another cellphone with data only. But I don't think there's anything to set that up easily.

[–] [email protected] 1 points 3 weeks ago

I wrote something myself because I wanted PGP support, but saw some apps on Google Play (I've been still using it back then). I can't recommend anything, sorry.

For calls - yeah, tough stuff. I'e been looking to do the same thing you did, and found there are GSM USB dongles (modems) that can work with Asterisk to forward calls, so you'd use a raspberry pi instead of a smartphone. But I never implemented it, people gradually stopped calling me and there was just no motivation.

[–] [email protected] 6 points 3 weeks ago (1 children)

I've used wi-fi calling fairly extensively mostly because I've lived in areas where there was zero cell service but ready access to internet (via Starlink or other wireless forms of it). One thing I do know is that my phone co. requests that I fill out a form specifying where I am living currently (whilst using it) so that if I ever need to contact emergency services they'll have a better idea of where to route the call to. For instance my phone number originates from Western BC but I could potentially be using wi-fi calling from anywhere in the province. I mention this to say, it appears my telco doesn't have a way to triangulate me with this service.

I can further attest that wi-fi call & text reception still works fine when I have a VPN running on the router that my mobile device is connecting to. Make of that information what you wish.

Though that I have read that wi-fi calling is atrocious for privacy reasons that I have not followed up on. Given the above I'm not sure how or why that would be the case, but basically if I'm in an area with cell coverage I turn it off. I've always meant to look deeper into how or why it might be bad (or worse) in some way.

[–] [email protected] 4 points 3 weeks ago

Interesting thanks. I'll dig into the privacy issue.

[–] [email protected] 5 points 3 weeks ago

I've tested wifi calling on AT&T, Verizon, and T-Mobile. How well it works (call quality, whether or not the call gets dropped, how often it gets dropped) has always been a crapshoot. Using a real VoIP client to connect to my Asterisk box? Significantly more stable and usable.

[–] [email protected] 3 points 3 weeks ago (1 children)

I used an iPod touch for calling over WiFi for years. It worked just fine, as long as one had a WiFi connection. Do it!

[–] [email protected] 2 points 3 weeks ago* (last edited 3 weeks ago)

Funny… I did the same thing. Chose Grand Central as my provider… who were then acquired by Google and became Google Voice :-/

These days I still have my GV number as it’s a known number, but I never call out on it. When possible I use Signal; I’ve also got burner talkatone numbers that change regularly, and Matrix/Element for any regular communication.

I figure the combination means that no provider has a full picture and all of those providers are unlikely to aggregate to the same databases.

[–] [email protected] 3 points 3 weeks ago (2 children)

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.

[–] [email protected] 3 points 3 weeks ago (1 children)

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.

[–] [email protected] 2 points 3 weeks ago (1 children)

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.

[–] [email protected] 1 points 3 weeks ago

There’s encryption and it is managed by the SIM.

[–] [email protected] 1 points 3 weeks ago (1 children)

I don't know what kinds of packets WiFi calling sends, but I would assume a public IP would be in there somewhere and, at least from a law enforcement perspective I can't imagine it would be too hard to get the address tied to it.

[–] [email protected] 1 points 3 weeks ago

It your provider has some endpoint somewhere. The thing is, if you’ve law enforcement involved it doesn’t really matter is it’s WiFi calling or a cellular call, they’ll still be able to tie it to you.

[–] [email protected] 3 points 3 weeks ago (1 children)

I strongly suggest you look into jmp.chat. That's what I've been using exclusively for the last 3 months , no problem. When I'm out, I just carry a prepaid 5G mobile modem with me, and have yet to miss a single call or sms (as far as I know). I haven't missed being attached to a mobile provider in the least. And since my mobile modem is unlocked and prepaid, I can just throw away the Sim if I don't want to use them anymore and use some other provider. Nevermind the huge savings since I moved to this flow.

[–] [email protected] 4 points 3 weeks ago (1 children)

Are you aware that using the same device with different SIMs is not helping your anonymity because IMEI is the same?

Power to you for not having GSM enabled on your phone though

[–] [email protected] 2 points 3 weeks ago

Oh, I know. The reason for switching Sims is because they do something I don't like, not for anonymity or even privacy. But it's good that you mention it here.

[–] 0x0 0 points 3 weeks ago

connected to a hotspot

These tend to use SIM-cards too. IF you want to avoid triangulation don't even put a SIM card in at all.