Comment by palata

E2EE fundamentally exists for situations where we don't want to trust the server. That's the whole idea of E2EE, right?

Of course it's not black or white, security is a gradient. But if you want to check today that you are running the legit client of ProtonMail in your browser, you do not have a practical way to do it. It is theoretically feasible, I guess (?), but far from practical. But I can walk you through the steps needed to do it today with Signal, for instance.

I think I put my limit there: it's not enough to run cryptography. Verifying the client has to be practical for the user. The way ProtonMail works in the browser is a nice way for Proton to minimise the data they collect, but it's not E2EE, because even as an advanced user I cannot practically verify the client they serve me. In other words, E2EE means (to me) that there can be some kind of guarantee if you put a reasonable amount of effort into verifying it. The browser doesn't provide that at all.

Interestingly, shipping a webapp in ElectronJS (which is terrible in terms of software, IMO) is different: you can have E2EE in an ElectronJS app.

And I'm assuming that's why Signal has a Desktop app (which I believe is ElectronJS) and not a web (as in, "loads in the browser") version.