Secure Phone calls and SMS

dasaint100

Hi,

I need to use a phone number for business and I'm looking at keeping the calls and texts as secure as possible.

Graphene OS with Wifi calling over a VPNrouter connection work with the SIM mobile number ok?

Airplane mode not the best as need to recieve calls. Unless the calls would get through via Wifi with Airplane mode still on?

Another query is that are 2FA apps more secure than texts for 2FA if kept in an offline profile? Would use Invisible Pro firewall to keep everything offline and not give network permission to the 2FA app.

Many thanks

DeletedUser115

Regular calls and SMS are inherently insecure. There is not much that can be done to "secure" them. Using WiFi calling/SMS over WiFi routes the traffic through another parties in addition to ISP so not sure if you'd gain anything by doing that.

I'd enable LTE-only mode and avoid having sensitive conversions over the phone/SMS.

Re: 2FA app, revoking network permission is enough, no need in Invisible for that.

dasaint100

Thanks. For the wifi calling, it would be through a VPN router. Would that be more secure than LTE calling?

de0u

dasaint100 For the wifi calling, it would be through a VPN router. Would that

Secure against which threats? Any cellular call is subject to SS7 hijacking. It's not all that common, but no amount of layering mobile routers in front of a cellular call protects against the cellular network being willing to reroute your call.

Deploying technological tools without a threat model can result in spending extra money and time without gaining effective security or privacy.

dasaint100

Also, was wondering how do you know if the call if being made through the wifi connection or a GSM cell connection? And what security a call going through wifi would have through the VPN router?

DeletedUser115

It's complicated and nuanced. Depends on secure from whom.

As you mentioned business calls, if the adversary is a competitor in a normal line of business, I'd say it doesn't make any meaningful difference.