So, I was told to not use Signal, so all that is left is Matrix. And I am not techy enough to have my own server and neither are my relatives, so Matrix.org is the only option
Unfortunately even with E2EE, the admins of a homeserver can still impersonate you or take over your channel.
Of course you could run your own instance, or maybe none of this is part of your threat model, but I felt like bringing it up either way.
even with E2EE, the admins of a homeserver can still impersonate you
No, they cannot. Your homeserver admin could create an impostor login session on your account, but it would be pointless with E2EE, because it would be flagged with an obviously visible warning. You and all of your contacts would see that the impostor session was not verified as you (this typically shows up as a bright red icon on the impostor and another one on the room they’re in). Also, the impostor would be unable to read your communications.
What do you have to say about this then?
In an encrypted room even with fully verified members, a compromised or hostile home server can still take over the room by impersonating an admin. That admin (or even a newly minted user) can then send events or listen on the conversations.
Perhaps we have a different definition of “impersonate”… not everyone will pay attention to unverified warnings, and afaik they can still communicate with people (just maybe not read old messages)… but I would love to be proven wrong.
a compromised or hostile home server can still take over the room
A compromised server could affect a denial of service attack against its users, of course. The attacker could do the same thing by simply turning off the server. That’s true on all platforms that use servers. A reasonable response would be to switch to a different server.
That admin (or even a newly minted user) can then send events
Exactly what events do you think would be dangerous?
or listen on the conversations.
No. End-to-end encryption ensures that only the intended endpoints can read the messages. Older Matrix clients have a setting to block the user from sending messages to unverified devices/sessions, in case they somehow don’t understand the meaning of a bright red warning icon. I think newer ones (e.g. Element X) enforce that mode; if you’re concerned about this, you could check for yourself, but…
not everyone will pay attention to unverified warnings
…unfortunately, there are no guarantees when trying to fix human behavior. If you need a messaging app to make it hard for your contacts to do something obviously foolish, then I suggest waiting until Matrix 2.0 is officially released and implemented in the clients. The beta versions of Element X, for example, look like everything is locked down to avoid human mistakes like the one you’re describing.
That isn’t what that document says. It says that they can impersonate you in non-E2EE scenarios. The clients I use warn me when a message isn’t properly encrypted so someone without E2EE keys can’t impersonate someone in an E2EE room.
That being said the general concept is a problem. I would love to see progress where all events from a user are signed by a device key and non-forgable. There is some thinking about this with portable identities (such as MSC2787) where you server is basically just storing and forwarding events but the root of trust is your identity and keys that you control. But none of this will land soon, not for many years.
