>Our attacks have shown that an fTPM cannot sufficiently protect its internal state against firmware or physical attacks. In such a scenario, a passphrase-only key protector of reasonable length provides better security than a TPM-only protector with a numeric PIN (5.3.1). This is in stark contrast to Microsoft’s claim that “BitLocker provides the most protection when used with a Trusted Platform Module” [29] (see also in 2.3). In fact, of all available protectors (seen in Figure 1), TPM-only is arguably the weakest protection strategy.
This might not be surprising to some, despite Windows hiding the GUI passphrase functionality behind some group policy settings, both "Require additional authentication at startup" and "Enhanced PIN", which isn't perhaps the most intuitive and a normal user might not even realize unless they notice the "normal" PIN is numerical-only. In any case, for the average person that might have their devices stolen, this is likely not to be a threat, but I think a passphrase should always be preferable, BitLocker doesn't support any better option.
This might not be surprising to some, despite Windows hiding the GUI passphrase functionality behind some group policy settings, both "Require additional authentication at startup" and "Enhanced PIN", which isn't perhaps the most intuitive and a normal user might not even realize unless they notice the "normal" PIN is numerical-only. In any case, for the average person that might have their devices stolen, this is likely not to be a threat, but I think a passphrase should always be preferable, BitLocker doesn't support any better option.