#Check BitLocker prerequisites
$TPMNotEnabled = Get-WmiObject win32_tpm -Namespace root\cimv2\security\microsofttpm | where {$_.IsEnabled_InitialValue -eq $false} -ErrorAction SilentlyContinue
$TPMEnabled = Get-WmiObject win32_tpm -Namespace root\cimv2\security\microsofttpm | where {$_.IsEnabled_InitialValue -eq $true} -ErrorAction SilentlyContinue
$WindowsVer = Get-WmiObject -Query 'select * from Win32_OperatingSystem where (Version like "6.2%" or Version like "6.3%" or Version like "10.0%") and ProductType = "1"' -ErrorAction SilentlyContinue
$BitLockerReadyDrive = Get-BitLockerVolume -MountPoint $env:SystemDrive -ErrorAction SilentlyContinue
$BitLockerDecrypted = Get-BitLockerVolume -MountPoint $env:SystemDrive | where {$_.VolumeStatus -eq "FullyDecrypted"} -ErrorAction SilentlyContinue
$BLVS = Get-BitLockerVolume | Where-Object {$_.KeyProtector | Where-Object {$_.KeyProtectorType -eq 'RecoveryPassword'}} -ErrorAction SilentlyContinue


#Step 1 - Check if TPM is enabled and initialise if required
if ($WindowsVer -and !$TPMNotEnabled) 
{
Initialize-Tpm -AllowClear -AllowPhysicalPresence -ErrorAction SilentlyContinue
}

#Step 2 - Check if BitLocker volume is provisioned and partition system drive for BitLocker if required
if ($WindowsVer -and $TPMEnabled -and !$BitLockerReadyDrive) 
{
Get-Service -Name defragsvc -ErrorAction SilentlyContinue | Set-Service -Status Running -ErrorAction SilentlyContinue
BdeHdCfg -target $env:SystemDrive shrink -quiet
}

<#Step 3 - Check BitLocker AD Key backup Registry values exist and if not, create them.
$BitLockerRegLoc = 'HKLM:\SOFTWARE\Policies\Microsoft'
if (Test-Path "$BitLockerRegLoc\FVE")
{
  Write-Verbose '$BitLockerRegLoc\FVE Key already exists' -Verbose
}
else
{
  New-Item -Path "$BitLockerRegLoc" -Name 'FVE'
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'ActiveDirectoryBackup' -Value '00000001' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'RequireActiveDirectoryBackup' -Value '00000001' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'ActiveDirectoryInfoToStore' -Value '00000001' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'EncryptionMethodNoDiffuser' -Value '00000003' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'EncryptionMethodWithXtsOs' -Value '00000006' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'EncryptionMethodWithXtsFdv' -Value '00000006' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'EncryptionMethodWithXtsRdv' -Value '00000003' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'EncryptionMethod' -Value '00000003' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'OSRecovery' -Value '00000001' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'OSManageDRA' -Value '00000000' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'OSRecoveryPassword' -Value '00000002' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'OSRecoveryKey' -Value '00000002' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'OSHideRecoveryPage' -Value '00000001' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'OSActiveDirectoryBackup' -Value '00000001' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'OSActiveDirectoryInfoToStore' -Value '00000001' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'OSRequireActiveDirectoryBackup' -Value '00000001' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'OSAllowSecureBootForIntegrity' -Value '00000001' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'OSEncryptionType' -Value '00000001' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'FDVRecovery' -Value '00000001' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'FDVManageDRA' -Value '00000000' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'FDVRecoveryPassword' -Value '00000002' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'FDVRecoveryKey' -Value '00000002' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'FDVHideRecoveryPage' -Value '00000001' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'FDVActiveDirectoryBackup' -Value '00000001' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'FDVActiveDirectoryInfoToStore' -Value '00000001' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'FDVRequireActiveDirectoryBackup' -Value '00000001' -PropertyType DWORD
  New-ItemProperty -Path "$BitLockerRegLoc\FVE" -Name 'FDVEncryptionType' -Value '00000001' -PropertyType DWORD
}
#>

#Step 4 - If all prerequisites are met, then enable BitLocker
if ($WindowsVer -and $TPMEnabled -and $BitLockerReadyDrive -and $BitLockerDecrypted) 
{
Add-BitLockerKeyProtector -MountPoint $env:SystemDrive -TpmProtector
Enable-BitLocker -MountPoint $env:SystemDrive -RecoveryPasswordProtector -SkipHardwareTest -UsedSpaceOnly -ErrorAction SilentlyContinue 
}

<#Step 5 - Backup BitLocker recovery passwords to AD
if ($BLVS) 
{
ForEach ($BLV in $BLVS) 
{
$Key = $BLV | Select-Object -ExpandProperty KeyProtector | Where-Object {$_.KeyProtectorType -eq 'RecoveryPassword'}
ForEach ($obj in $key)
{ 
Backup-BitLockerKeyProtector -MountPoint $BLV.MountPoint -KeyProtectorID $obj.KeyProtectorId
}
}
}
#>