BitLocker Disk Encryption
BitLocker Disk Encryption (BDE) is Full Volume Encryption solution by Microsoft first included with the Enterprise and Ultimate editions of Windows Vista. It is also present in Windows 7 along with a system for encrypting removable storage media devices, like USB, which is called BitLocker To Go. Unlike previous versions of BitLocker, BitLocker To Go allows the user to protect volumes with a password or smart card.
Volumes encrypted with BitLocker will have a different signature than the standard NTFS header. Instead, they have in their volume header (first sector): 2D 46 56 45 2D 46 53 2D or, in ASCII, -FVE-FS-.
These volumes can be identified by the BitLocker GUID/UUID: 4967d63b-2e29-4ad8-8399-f6a339e3d00.
The actual data on the encrypted volume is protected with either 128-bit or 256-bit AES and optionally diffused using an algorithm called Elephant. The key used to do the encryption, the Full Volume Encryption Key (FVEK) and/or TWEAK key, is stored in the BitLocker metadata on the protected volume. The FVEK and/or TWEAK keys are encrypted using another key, namely the Volume Master Key (VMK). Several copies of the VMK are also stored in the metadata. Each copy of the VMK is encrypted using another key, also know as key-protector key. Some of the key-protectors are:
- TPM (Trusted Platform Module)
- Smart card
- recovery password
- start-up key
- clear key; this key-protector provides no protection
- user password
BitLocker has support for partial encrypted volumes.
BitLocker To Go
Volumes encrypted with BitLocker To Go will have a hybrid encrypted volume, meaning that part of the volume is unencrypted and contains applications to unlock the volume and the other part of the volume is encrypted. The "discovery drive" volume contains BitLocker To Go Reader to read from encrypted volumes on versions of Microsoft Windows without BitLocker support.
To view the BitLocker Drive Encryption (BDE) status on a running Windows system:
To obtain the recovery password for volume C:
manage-bde.exe -protectors -get C: -Type recoverypassword
Or just obtain the all “protectors” for volume C:
manage-bde.exe -protectors -get C:
- Wikipedia entry on BitLocker
- Accessing Bitlocker volumes from linux, by Nitin Kumar and Vipin Kumar, 2008
- Implementing BitLocker for Forensic Analysis, Digital Investigation, by Jesse D. Kornblum, 2009
- BitLocker Drive Encryption (BDE) format specification, by the libbde project, March 2011
- Microsoft's Step by Step Guide
- Microsoft Technical Overview
- An Introduction to Security in Windows 7
- Microsoft FAQ
- Microsoft Description of the Encryption Algorithm
- Cold Boot Attacks, Full Disk Encryption, and BitLocker
- What's New in BitLocker in Windows 8