BitLocker Drive Encryption is a full disk encryption feature included with Microsoft's Windows Vista Ultimate, Windows Vista Enterprise and Windows Server 2008 operating systems designed to protect data by providing encryption for entire volumes.

By default it uses the AES encryption algorithm in CBC mode with a 128 bit key, combined with the Elephant diffuser for additional disk encryption specific security not provided by AES.

BitLocker is only available in the Enterprise and Ultimate editions of Windows Vista.

In the RTM release of Windows Vista, only the operating system volume could be encrypted using the GUI and encrypting other volumes required using WMI-based scripts included in Windows Vista in the %Windir\System32 folder.

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