When facing the lock screen to enter my credentials, my Mac running macOS 10.13 High Sierra asks for a PIN instead of my password. This has happened 4 times within the last months. The only solution is to force a shutdown and restart. Then my MacBook will ask for my password again. I have never setup a PIN and it's not the screen I would get if I lock my MacBook through Find my Mac.

Unfortunately, only the search results regarding Find my Mac come up when searching for PIN and MacBook. I hope someone can help me by referring to the screenshot above.

What is this PIN and why is macOS asking for it? How can I prevent macOS from asking for a PIN?

  • Do you have a CAC (Common Access Card) reader attached to your MacBook? – IconDaemon Sep 11 '18 at 11:56
  • No, I don't have a CAC reader. – Thomas Zuberbühler Sep 11 '18 at 13:03
  • Have you ever locked this MB with iCloud Find my Mac? Do you use two-factor authentication on your Apple ID? This thread at Apple Discussions has more clues. – IconDaemon Sep 11 '18 at 14:30
  • I do have a Yubikey but it was not in the USB slot and never used for MacOS. I am using it for 2-factor authentication on the internet. – Thomas Zuberbühler Sep 19 '18 at 12:22
  • And I disabled 2-factor authentication for my Apple ID online. I was assuming that. – Thomas Zuberbühler Sep 19 '18 at 12:23

You have your Yubi key in the USB port at some point, put the Yubi key in and enter your Yubi Pin this will unlock your screen

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