I have a 2018 Mac Mini with an encrypted system volume that should only be unlockable by a single user.

It used to be the case that when I started up my computer I get a brief apple logo then see a Filevault password prompt (stripped down login window) for only a single user, and after entering the password for that user I'd then get a progress bar as the system unlocked and started up.

However, ever since 10.15.6 this has not been the case; when I start up after shutting down my computer it gives me the apple logo with a progress bar that reaches the end before displaying a full login window for all users

In other words, for some reason my T2 chip is no longer prompting for a Filevault password at all before unlocking the disk, it's just unlocking it automatically every single time, completely defeating the point. The issue also occurs under 10.15.7.

I know that the T2 chip doesn't lock a volume when restarting during system updates, but it's like that behaviour has become permanently enabled such that it's also affected shutdown and startup, which is a major security flaw.

Is there any way I can reset this without losing access to the disk?

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    I think it's 'normal' for the admin account's credentials to be used automatically to get the login prompt. You only get asked for a password immediately if none of the user accounts have the keys. Password is still required to 'get in'. – benwiggy Oct 14 '20 at 10:50
  • It's never been normal before; in the past I would get a password prompt before the progress bar appeared, because my password is supposed to be required before the volume is unlocked. If Apple has changed this behaviour then I'm never using another system from them again. – Haravikk Oct 15 '20 at 11:47
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    No: there's no change. The behaviour depends on how you enable FileVault: if you enable it from the Admin user account, then it goes through to the login; if you use other methods, like choosing an encrypted format, or pre-OS installation, then it asks for the password to unlock the disk at the very start. – benwiggy Oct 15 '20 at 11:58
  • I haven't changed anything with regards to how Filevault was setup; about two months ago it was working as expected (must enter password before any progress bar appears), now it doesn't. I have changed nothing, except to install system updates. – Haravikk Oct 16 '20 at 15:55

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