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    @allexj: 1) Secure Boot in the context of BitLocker prevents the key(s) from being exposed to kernel-level rootkits. If the kernel has been manipulated, the TPM can detect that its signature no longer matches the known signature from Microsoft. Userspace programs are not covered by Secure Boot, so this only protects against particular malware. 2) Brute-forcing a 256-bit key is hopeless, so if the VMK is protected with a TPM, then an attacker cannot simply remove the disk from the system. They would either have to be physically present or attack the system after it has been unlocked. Commented Dec 29, 2024 at 14:38
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    @allexj: 2.1) If the key is protected with both a TPM and a password, then, yes, an attacker with physical access only has to brute-force the password. 2.2) Correct, the VMK can only be decrypted after you’ve passed all checks of all key protectors. In your case, you have a TPM and a PIN, so the VMK isn’t available until both the Secure Boot verification was successful and you’ve entered the correct pin. Commented Dec 29, 2024 at 15:25
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    @allexj: Correct. A TPM in conjunction with Secure Boot helps against malicious bootloaders and kernel rootkits (but not other malware). In principle, TPM 2.0 supports arbitrarily complex policies, so it could do a lot more to protect the VMK, e.g., require the user to prove ownership of a separate key (ideally stored on a smartcard or some other hardware token). But I don’t believe there are any plans for implementing this in BitLocker. Commented Dec 29, 2024 at 16:49
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    @allexj: The text talks about the (private) key inside the TPM which decrypts the VMK, not the VMK itself. The VMK is eventually decrypted and provided to the OS as plaintext, but the key used by the TPM for this purpose stays within the TPM and is never exposed. Commented Dec 30, 2024 at 15:19
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    @allexj: Yes, the sensitive area of the key created with tpm2_createprimary stays within the TPM and is never exposed to the outside world. The sealed data ("testpw") does get exposed when unsealing it with tpm2_unseal. Commented Dec 30, 2024 at 16:20