[bri3d]

I discussed this at length in the last thread: https://news.ycombinator.com/item?id=48137059

We know how PIN-locked BitLocker works, and it requires unwrapping using a key sealed behind a TPM PIN policy and stretching it using the PIN itself. So we can deduce that this would require that:

* The attacker was able to bypass the TPM PIN sealing policy _and_ brute-force the stretching applied to the decrypted key. Brute-forcing the stretch is plausible on a "lots of expensive stuff" timeline but not an easy attack. Bypassing TPM PIN policy across multiple platforms would be something quite incredible. Given that TPMs are implemented by multiple vendors across multiple fundamental architectural approaches, and aren't based on a universal reference implementation, it would be rather bizarre to find a mistake in many or all of them.

* There is a secret volume key stored on a volume which can be decrypted by another mechanism. This would be a backdoor, but seems vanishingly unlikely given the amount of research which has been applied against BitLocker historically.

* The attacker is at some point able to inject something which allows them to observe the victim applying the PIN. There could be an attack here but it isn't nearly as interesting.