To both unlock a BitLocker encrypted hard drive and log on at the same time is not possible. When starting up a computer that has its boot drive encrypted by BitLocker, the bitlocker software will prompt for the user to enter their PIN number in before BitLocker allows the OS to start. You can still allow your users to set their BitLocker PIN number to be the same as their domain logon password by turning on enhanced PINs for startup in Group Policy. To do this:
- Create or edit an existing GPO on you network.
- Browse to Computer Configuration à Policies à Administrative Templates à Windows Components à BitLocker Drive Encryption à Operting System Drives.
- Open the setting for Allow Enhanced PINs for startup.
Normally only numbers are used for the PIN. With this setting, all valid characters allowed for a domain password can be used for a startup PIN. If you are looking for a single sign on option with BitLocker, it is not possible. Should your users set their domain password to be identical to the BitLocker PIN, they run the risk of inadvertently typing the wrong PIN in after changing their domain password. Should this happen, the recovery key would be needed to gain access to the hard drive.
Using this method also negates the two factor authentication that is provided with BitLocker. For this reason, I recommend that users do not utilize the same PIN and domain password.