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TPM and Bitlocker


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3 replies to this topic

#1 TheJokerz

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Posted 21 December 2017 - 01:00 PM

Long story short, I recently updated some of my hardware on my desktop(GPU, CPU, added HDD). I had a windows 10 install that was a year old, and wanted to do a clean install. So WIN 10 Fall Creator update was out so I figured what a better time than now to do a clean install. Before I forget to mention, I had the old install encrypted with Bitlocker. I am just now getting around to setting up Bitlocker on the fresh install of windows 10. Here is my issue, every time I restart it will ask for my recovery key. I have double checked the UEFI twice to ensure the TPM module is enabled and has the correct settings.

Now here a second question. I have poked around on the net and have come to the conclusion that I should have maybe cleared the TPM before I encrypted again. Not sure how true this really is. I have also seen that there are a couple of commands that I can run for example:

Manage-bde –protectors –delete C: -type TPM

Manage-bde –protectors – add C: -tpm

These are supposed to repopulate the TPM chip. My only issue is that I really do not want to have to reinstall windows because the drives became non decryptable.

Is there anything I can do??
Thanks in advance!


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#2 Didier Stevens

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Posted 23 December 2017 - 03:58 AM

If I understand correctly:

 

1) You had Windows (let's call this A) installed on your desktop with BitLocker using TPM.

2) You updated the hardware (but not the TPM)

3) You installed a new version of Windows (let's call this B ) over Windows A.

4) Windows B was not encrypted with BitLocker when you installed it

5) Later you encrypted Windows B (BitLocker/TPM)

 

Is this what happened?


Edited by Didier Stevens, 23 December 2017 - 03:59 AM.

Didier Stevens
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#3 TheJokerz

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Posted 09 January 2018 - 10:18 AM

If I understand correctly:

 

1) You had Windows (let's call this A) installed on your desktop with BitLocker using TPM.

2) You updated the hardware (but not the TPM)

3) You installed a new version of Windows (let's call this B ) over Windows A.

4) Windows B was not encrypted with BitLocker when you installed it

5) Later you encrypted Windows B (BitLocker/TPM)

 

Is this what happened?

Yes this is correct in a nut shell.  Sorry for such a long delay, I did not realize you responded.  Also I have already decrypted the drive as I could not get this to work appropriatly.  I have has gone into TPM management and cleared the TPM in the snap in console.  This also did not fix the issue. 


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#4 zzz00m

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Posted 29 January 2018 - 12:30 PM

If you enable the policy in Group Policy Editor "Require additional authentication at startup", you can use BitLocker without a TPM, and this way it only asks for your BitLocker password when you boot.  I had to go this route since my motherboard is not equipped with a TPM, but I still wanted to encrypt my SSD system drive.

 

Check option "Allow BitLocker without a compatible TPM (requires a password or a startup key on a USB flash drive"

 

"This policy setting allows you to configure whether BitLocker requires additional authentication each time the computer starts and whether you are using BitLocker with or without a Trusted Platform Module (TPM). This policy setting is applied when you turn on BitLocker."






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