BitLocker is a software-based disk encryption feature that is part of Enterprise and Ultimate editions of Microsoft Windows 7 and all editions of Windows Server 2008 R2. It provides confidentiality to data at rest on appropriately powered down computers. BitLocker is typically used with a Trusted Platform Module (TPM).
BitLocker supports a number of different “Key Protectors”. A Key Protector defines how many, and what, authentication factors are used. BitLocker supports a number of 1-factor, 2 factor and 3-factor authentication options.