This policy setting controls whether a BitLocker-protected computer that is connected to a trusted wired Local Area Network (LAN) and joined to a domain can create and use Network Key Protectors on TPM-enabled computers to automatically unlock the operating system drive when the computer is started.If you enable this policy clients configured with a BitLocker Network Unlock certificate will be able to create and use Network Key Protectors.To use a Network Key Protector to unlock the computer both the computer and the BitLocker Drive Encryption Network Unlock server must be provisioned with a Network Unlock certificate. The Network Unlock certificate is used to create Network Key Protectors and protects the information exchanged with the server to unlock the computer. You can use the group policy setting "Computer Configuration\Windows Settings\Security Settings\Public Key Policies\BitLocker Drive Encryption Network Unlock Certificate" on the domain controller to distribute this certificate to computers in your organization. This unlock method uses the TPM on the computer so computers that do not have a TPM cannot create Network Key Protectors to automatically unlock with Network Unlock.If you disable or do not configure this policy setting BitLocker clients will not be able to create and use Network Key Protectors.Note: For reliability and security computers should also have a TPM startup PIN that can be used when the computer is disconnected from the wired network or the server at startup.
Windows Components\BitLocker Drive Encryption\Operating System Drives
At least Windows Server 2012 or Windows 8