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I have a Microsoft Surface tablet, removed the encrypted drive, and used an SSD adapter to access it.

Therefore Bitlocker detected that the SSD is not on the original device and it asked for my encryption key.

Where is that information stored, or how does Bitlocker make the determination that it's on a different device? From data on the SSD itself? In some SSD partition?

Once I reinstalled it on the tablet, it worked flawlessly. So how does Bitlocker know?

Thanks in advance!

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  • Where is that information stored?...The encryption key or the fact the SSD isn't in the original device?
    – I say Reinstate Monica
    Jun 13, 2017 at 13:53
  • Please edit your question to clarify that point. BTW, Welcome to Super User.
    – I say Reinstate Monica
    Jun 13, 2017 at 14:08
  • Your Microsoft Surface has a TPM. You will have to provide the recovery key to access the drive, in order to decrypt the drive. Please research how Bitlocker works in conjunction with a TPM for more information. "Where is that information stored, or how does Bitlocker make the determination that it's on a different device?" - The TPM is missing. "In some SSD partition?" - No;
    – Ramhound
    Jun 13, 2017 at 14:50
  • Thank you so much for your response. So Bitlocker works with a TPM microcontroller on my tablet?
    – user738178
    Jun 13, 2017 at 15:21

1 Answer 1

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BitLocker does an integrity check during boot. The exact mechanism is not published by Microsoft, as far as I know, but it observes a lot of settings. It probably stores a signature of the system on the encrypted drive.

Your tablet also has a TPM implementation. I'm not certain, but I think there is no separate microcontroller for this, as it is a software solution, using special CPU instructions. Windows detects that the "usual" TPM is not available, and it can't proceed without any above mentioned checks. The TPM contains the encryption key, and it is not available, so it cannot decrypt it. This is not some software limitation, that you can bypass.

However, you can still access the contents of your SSD, using the recovery key. When you setup BitLocker, it urges you to print the recovery key. It might also be stored in your Microsoft account.

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  • Thank you, exactly the response I was looking for! So it's impossible to bypass Bitlocker encryption (or to decrypt the drive) without the key or reinstalling it on the original device.
    – user738178
    Jun 13, 2017 at 16:41
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    If you put the disk back into the tablet it was originally encrypted with then, yes, it won't ask you for the key as the TPM mechanism will have the key to unlock the volume for booting.
    – Kinnectus
    Jun 13, 2017 at 16:44

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