What is this future UX you're imagining? How does the future solve the contacts book/short identifiers problem?

I'm not saying its an amazing experience or solves the problem systematically. Again, some people simply don't need these features. You can literally just take part of the public key and that's it. That is totally fine for some use-cases.

Then use urbit. It already exists.

Yeah but the whole point of Signal is to allow secure very secure communication. With little effort they could allow this usecase. It would address a major criticism and they already have the underlying infrastructure.

But I guess you can just keep moving the goal post.

I don't understand how that's moving the goal post. Urbit developed a novel way to phonetically encode larger amounts of entropy than people are used to dealing with in order to build a network where your cryptographic identifier is your namespace and prime identity. You can spin up an urbit ship/planet and securely message anybody on the network using that short identifier. You suggested just using part of somebody's public key as an identifier directly. Urbit basically does that and a whole lot more.

I suspect it would be rather trivial to cut out the phone parts of Signal and have a UI where you paste in the first 8 characters of pubkeys and it matches those. Why not try building it?

I know nothing of Urbit.

My point was just that there is a simple technical solution that Signal could apply if they wanted to make people happy who have no phone number and its moving the goal post to say 'use some other app'.

Claiming that the solution is simple is the problem. Signal actually has been trying to add usernames for years. It involves an account, contacts book, trusting Signal, trusting Intel, SGX remote attestation, Raft, and passpins. They are getting reamed for it because it's not really possible to treat a 4 digit pin as a strong password but they're trying to do it anyway. It inverts the whole value prop of Signal on its head. That's my point here. The reason I'm saying use something else is because it's not simple like you claim. And it changes Signal's model enough that people are leaving Signal because it's not what they signed up for.

Put simply, telling Signal to add usernames is like telling the existing users to "use something else" because that's what Signal must turn itself into to satisfy the "I need usernames right now" crowd.

Again, I'm not talking about usernames, I'm talking about public keys.

Well you should try: https://getsession.org. It's a fork of Signal with pubkeys instead of phone numbers.

I mostly used to Matrix already. I prefer the way they work and I prefer their approach.

The difference between Matrix and Signal is that my mom can use Signal

Just like this website. Usernames. Easy peasy.

And how do you claim a username?

By knowing the password?

Where do you put the passwords DB?