Windows 7 / Getting Started

BitLocker Phases

The stages of BitLocker startup are as follows:

  • System integrity verification (if a TPM is present) Features of the computer and the Windows Boot Manager write values to the PCRs of the TPM as the boot process proceeds, including a measurement of the MBR executable code.
  • User authentication (optional) If user authentication is configured, the Windows Boot Manager collects a key from USB storage or a PIN from the user.
  • VMK retrieval The Windows Boot Manager requests that the TPM decrypt the VMK. If the hashes of the measurements written to the PCR match those taken when BitLocker was set up, the TPM will supply the VMK. If any measurement does not match the recorded value, the TPM does not supply the decryption key, and BitLocker gives the user the option to enter the recovery key.
  • Operating system startup At this point, the Windows Boot Manager has validated the system integrity and now has access to the VMK. The VMK must be passed to the operating system loader; however, the Windows Boot Manager must avoid passing it to a potentially malicious operating system loader and thus compromising the security of the VMK. To ensure that the operating system loader is valid, the Windows Boot Manager verifies that operating system loader executables match a set of requirements. The Windows Boot Manager also verifies that the boot configuration data (BCD) settings have not been modified. It does so by comparing them to a previously generated digital signature known as a message authenticity check (MAC). The BCD MAC is generated using the VMK, ensuring that it cannot be easily rewritten.
    After the operating system loader is started, Windows can use the VMK to decrypt the FVEK and then use the FVEK to decrypt the BitLocker-encrypted volume. With access to the unencrypted data on the volume, Windows loads normally.

Prior to transitioning to the operating system, the OS Loader ensures that it will hand off at most one key (VMK) to the operating system. Prior to handing off the key to the operating system, the following conditions must apply:

  • All features, up to and including BOOTMGR, must be correct. If they are not correct, the VMK will not be available.
  • The VMK must be correct to validate the MAC of the metadata. BOOTMGR verifies this MAC.
  • OS Loader must be the loader approved by metadata associated with the VMK. Verified by BOOTMGR.
  • BCD settings must be the settings approved by metadata associated with the VMK. Verified by BOOTMGR.
  • The VMK must correctly decrypt the FVEK stored in the validated metadata. Verified by BOOTMGR.
  • The FVEK must successfully decrypt data stored on the volume. An incorrect FVEK will result in invalid executable code or invalid data. In some cases, this is caught by code integrity.
    • The Master File Table (MFT) must be encrypted by the correct FVEK to access all files.
    • Phase 0 drivers, including Fvevol.sys, must be encrypted by the correct FVEK.
    • Registry must be encrypted by the correct FVEK.
    • Kernel and Hardware Abstraction Layer (HAL) must be encrypted by the correct FVEK.
    • Phase 1 features must be encrypted by the FVEK because Fvevol.sys (encrypted by the FVEK) will only decrypt using the same FVEK.
    • Phase 2 features must also be encrypted by the FVEK as stated in the previous entry.

The last point is particularly important, and it is true only if the data on the volume is entirely encrypted. In other words, a volume in which encryption is paused halfway through is not secure.

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In this tutorial:

  1. Managing Disks and File Systems
  2. Overview of Partitioning Disks
  3. How to Choose Between MBR or GPT
  4. Converting from MBR to GPT Disks
  5. GPT Partitions
  6. Choosing Basic or Dynamic Disks
  7. Working with Volumes
  8. How to Create a Simple Volume
  9. How to Create a Spanned Volume
  10. How to Create a Striped Volume
  11. How to Resize a Volume
  12. How to Delete a Volume
  13. How to Create and Use a Virtual Hard Disk
  14. File System Fragmentation
  15. Backup And Restore
  16. How File Backups Work
  17. File and Folder Backup Structure
  18. How System Image Backups Work
  19. How to Start a System Image Backup from the Command Line
  20. How to Restore a System Image Backup
  21. System Image Backup Structure
  22. Best Practices for Computer Backups
  23. How to Manage Backup Using Group Policy Settings
  24. Previous Versions and Shadow Copies
  25. How to Manage Shadow Copies
  26. How to Restore a File with Previous Versions
  27. How to Configure Previous Versions with Group Policy Settings
  28. Windows ReadyBoost
  29. BitLocker Drive Encryption
  30. How BitLocker Encrypts Data
  31. How BitLocker Protects Data
  32. TPM with External Key (Require Startup USB Key At Every Startup)
  33. TPM with PIN (Require PIN At Every Startup)
  34. TPM with PIN and External Key
  35. BitLocker To Go
  36. BitLocker Phases
  37. Requirements for Protecting the System Volume with BitLocker
  38. How to Enable the Use of BitLocker on the System Volume on Computers Without TPM
  39. How to Enable BitLocker Encryption on System Volumes
  40. How to Enable BitLocker Encryption on Data Volumes
  41. How to Manage BitLocker Keys on a Local Computer
  42. How to Manage BitLocker from the Command Line
  43. How to Recover Data Protected by BitLocker
  44. How to Disable or Remove BitLocker Drive Encryption
  45. How to Decommission a BitLocker Drive Permanently
  46. How to Prepare AD DS for BitLocker
  47. How to Configure a Data Recovery Agent
  48. How to Manage BitLocker with Group Policy
  49. The Costs of BitLocker
  50. Windows 7 Encrypting File System
  51. How to Export Personal Certificates
  52. How to Import Personal Certificates
  53. How to Grant Users Access to an Encrypted File
  54. Symbolic Links
  55. How to Create Symbolic Links
  56. How to Create Relative or Absolute Symbolic Links
  57. How to Create Symbolic Links to Shared Folders
  58. How to Use Hard Links
  59. Disk Quotas
  60. How to Configure Disk Quotas on a Single Computer
  61. How to Configure Disk Quotas from a Command Prompt
  62. How to Configure Disk Quotas by Using Group Policy Settings
  63. Disk Tools
  64. EFSDump
  65. SDelete
  66. Streams
  67. Sync
  68. MoveFile and PendMoves