You could encrypt the (T)IMSI somehow, but using what? You could use a pre-shared key but then to support roaming this would have to be shared among operators b

You could encrypt the (T)IMSI somehow, but using what? You could use a pre-shared key but then to support roaming this would have to be shared among operators but that’s trivial to defeat for state actors. You could go for an asymmetric scheme like HTTPS but there has to be some way for the network to “get back to you” much as you have to reveal your IP Address to kick off a TLS handshake. You can’t rely on alternative addressing schemes because then how do you allocate these? You have to stick your head over the parapet at some stage. This is the nature of the zero-trust peer-to-peer nature of the global telephony system. I wonder if there’s an application for some kind of a blockchain here .. EDIT just to note, your example of laptops and wireless APs, you must reveal at the very least your MAC address which is if anything less secure because it doesn’t change - at least not trivially.