BitLocker is a software-based disk encryption feature that is part of Enterprise and Ultimate editions of Microsoft Windows Vista and all editions of Windows Server 2008. 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.