This policy setting allows you to configure whether or not enhanced startup PINs are used with BitLocker. Enhanced startup PINs permit the use of characters including uppercase and lowercase letters, symbols, numbers, and spaces. This policy setting is applied when you turn on BitLocker. The recommended state for this setting is: Enabled. Rationale: A numeric-only PIN provides less entropy than a PIN that is alpha-numeric. When not using enhanced PIN for startup, BitLocker requires the use of the function keys [F1-F10] for PIN entry since the PIN is entered in the pre-OS environment before localization support is available. This limits each PIN digit to one of ten possibilities. The TPM has an anti-hammering feature that includes a mechanism to exponentially increase the delay for PIN retry attempts; however, an attacker is able to more effectively mount a brute force attack using a domain of 10 digits of the function keys.
To establish the recommended configuration via GP, set the following UI path to Enabled: Computer Configuration\Policies\Administrative Templates\Windows Components\BitLocker Drive Encryption\Operating System Drives\Allow enhanced PINs for startup Note: This Group Policy path may not exist by default. It is provided by the Group Policy template VolumeEncryption.admx/adml that is included with the Microsoft Windows 7 & Server 2008 R2 Administrative Templates (or newer). Impact: All new BitLocker startup PINs set will be enhanced PINs. Note: Not all computers enable full keyboard support in the Pre-OS environment. Some keys may not be available. It is recommended this functionality be tested using the computers in your environment prior to it being deployed. Default Value: Disabled. (Enhanced PINs will not be used.)