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Cake day: June 15th, 2023

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  • Microsoft uses TPM PCRs 7+11 for BitLocker which is more secure than the Linux implementations mentioned in the article.

    PCR 7 is the Secure Boot measurement which means it can’t be unlocked unless every signed boot component has not been tampered with up to the point of unlock by the EFI bootloader. PCR 11 is simply flipped from a 0 to a 1 by the bootloader to protect the keys from being extracted in user land from an already booted system.

    The article is correct that most Linux implementations blindly following these kinds of “guides” are not secure. Without additional PCRs, specifically 8 and 9 measuring the grub commands (no single-user bypass) and initrd (which is usually on an unencrypted partition), it is trivial to bypass. But the downside of using these additional PCRs is that you need to manually unlock with a LUKS2 password and reseal the keys in TPM whenever the kernel and or initrd updates.

    Of course to be really secure, you want to require a PIN in addition to TPM to unlock the disk under any OS. But Microsoft’s TPM-only implementation is fairly secure with only a few advanced vulnerabilities such as LogoFAIL and cold boot attacks.








  • Did you have to install an app called Company Portal or Intune? If no, then they probably don’t have access to your device, except for possibly being able to selectively wipe school data. They could also be using another MDM solution like Airwatch, but again, you would have had to have installed something (and unlikely, since universities get massive discounts on Microsoft licensing).

    Even if you do have Company Portal, it doesn’t necessarily mean it’s managed as it’s still used to broker communication and authentication between Office apps on Android. The app itself would be able to tell you if the device is managed.

    And as the other poster mentioned, if they had you install a root certificate for the university they can intercept and inspect HTTPS traffic from your device while on their network. But that still doesn’t give them access to the data-at-rest on your device.