> I do not understand the Noise protocol but couldn't an ISP or a government pretend to be man in the middle, between let us say a Signal user and its servers?

> I do not understand the Noise protocol but couldn't an ISP or a government pretend to be man in the middle, between let us say a Signal user and its servers? Signal messenger uses the Signal Protocol. Like most every other end to end encrypted messaging scheme, Signal uses cryptographic signatures (or the equivalent in the case of Signal) to insure that you are talking to who you think you are talking to. You end up with a sort of identity number (a really long one). As long as you can insure that you have the right identity number for your correspondent you can be sure that you are connected to that correspondent directly with no interlopers. In person you can use something like a QR code to do this. Otherwise you can try comparing numbers over the phone. There is a whole discussion of Signal "safety numbers" and how they relate to a MITM attack here: * https://sequoia-pgp.org/blog/2021/06/28/202106-hey-signal-great-encryption-needs-great-authentication/ https://sequoia-pgp.org/blog/2021/06/28/202106-hey-signal-gr... From that I get that in most cases it would be possible to MITM a Signal connection because most users are unable to figure out how to verify their safety numbers.