I was thinking of RCS security apparently, but was mainly talking about what’s theoretically possible.

There’s nothing stopping someone creating a E2E encrypted SMS app. The medium doesn’t matter, only the data. You could have end to end encrypted carrier pigeons if you want.

Yep, you lock with the public key and unlock with the private.

You can’t unlock with the public, it’s one way only

don’t they also receive the public keys and can then also decrypt the messages??

A public key is used to encrypt a message, you need the private key to decrypt.

That’s why you have public key servers. it doesn’t matter who has the public key, all they can do with it is encrypt information that only the private key holder can decrypt.

The more I think about it, the more I am convinced I don’t understand how any encryption works because the intended recipient needs the key to decrypt it

The way it was explained to me that finally made it click was so:

Imagine you have a lockable box (public key) and a key (private key), the box is empty so you give it to your friend. it doesn’t matter if anyone sees the open box because there’s nothing in it. your friend puts something private for you in the box and locks it. People see the box as he’s bringing it to you but they can’t see what’s in the box because neither him nor the people watching have the key to the box; only you do. once it gets to you you can open the box with your key

It’s not misinformation. SMS can have end to end encryption if the messages exchanged between two people in a conversation are encrypted.

It’s an add on, in much the way PGP encryption works for email. the first handshake is unencrypted and includes each participants public keys, after that you can have it automatically encrypt each message

you can configure some phones to encrypt all sms messages.

It’s a bit like PGP email though in that, despite it working, no one seems to use it