Change BitLocker Drive encryption to XTS-AES 256 during OSD with #ConfigMgr

Windows 10 Current Branch (1607 & 1703) is using a default drive encryption of XTS-AES 128 if you encrypt the disk during OSD using ConfigMgr Current Branch.
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Command above: manage-bde -status

Some customer maybe have the requirement to change the default to a different mode like XTS-AES 256.

This can be changed using a GPO or CIs in ConfigMgr but then you have first to decrypt the disk, assign the new policy and encrypt the disk again. This is annoying and not very user & admin friendly.

Since a while ConfigMgr is using an option called Pre-provision Bitlocker. This step in the TS is encrypting only the currently used diskspace. As it is in WinPE this is a very small part of the disk and also a quick step. But this step is using the command “manage-bde.exe  -on C: -used” and you are not able to change the encryption method.

Solution

To change the method to XTS-AES 256 or a different method, use following registry key just before the Pre-provision BitLocker step:

cmd /c reg.exe add HKLM\SOFTWARE\Policies\Microsoft\FVE /v EncryptionMethod /t REG_DWORD /d 7 /f

The DWORD value 7 ist setting the method to XTS-AES 256. Use the list bellow to assign a different method:

Value 3, AES_128:
The volume has been fully or partially encrypted with the Advanced Encryption Standard (AES) algorithm, using an AES key size of 128 bits.

Value 4, AES_256
The volume has been fully or partially encrypted with the Advanced Encryption Standard (AES) algorithm, using an AES key size of 256 bits.

Value 6, XTS_AES128 *
The volume has been fully or partially encrypted with the Advanced Encryption Standard (AES) algorithm, using an XTS-AES key size of 128 bits. – This is the default of Windows PE 10.0.586.0 (1511 Release)

Value 7, XTS_AES256 *
The volume has been fully or partially encrypted with the Advanced Encryption Standard (AES) algorithm, using an XTS-AES key size of 256 bits.

* Only supported for deployments of Windows 10 images build version 1511 or higher

The Task Sequence step I used is a command line and is configured to run just before “Pre-provision” BitLocker:

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This has been testet with the Windows 10 Enterprise Builds 1607 (Anniversary) & 1703 (Creators).