> We transform your passphrase on your computer into two different, unrelated values. With one value, you cannot derive the other0. We send an authentication token, derived from your passphrase, to the server as the password-equivalent. And the encryption key derived from your passphrase never leaves your computer.

Ah, looks like they still do. My mistake. I was harkening back to the old Sync protocol which just gave you a decryption key, rather than any account system. From this post it seems they've just integrated it with your password, if your link is describing the present method.

What I had in mind was this: https://blog.mozilla.org/services/2014/05/08/firefox-account.... i.e., back in the day you could self-host Firefox Sync, like a Nextcloud. It seems this is still possible, though not straightforwardly: https://discourse.mozilla.org/t/how-to-self-host-fxa-and-syn...

> back in the day you could self-host Firefox Sync

Yep -- and this is why I personally think there's something rotten in Mozilla.

At the beginning there were 3rd party extensions to sync bookmarks that just allowed you to point to any webdav server (which is trivial to self-host). At some point Mozilla decided to implement this functionality as a 1st party extension, thereby displacing all the other 3rd party extensions that were doing the same (and later on outright killing these extensions, by changing the APIs and making the new ones buggy).

And once the other extensions were killed, they started to make it harder and harder to self-host. Up to the point I gave up self-hosting Firefox Sync; it's just not worth the effort, and I really see absolutely no need for such a huge infrastructure for what could be done with plain clothes WebDAV.

That is the day Mozilla earned my distrust. I basically use Firefox (or its forks) just because there is no other choice.