What feature provided at the Windows Server $2012$ domain functional level creates a secure channel or tunnel between a client seeking authentication for a computer service and the server providing secure access keys for secure communications?

Flexible Authentication Secure Tunneling $($FAST$)$

Secure Tunneling Authentication Protocol $($STAP$)$

Kerberos Hardening Policy $($KHP$)$

Tunneled Authentication Security $($TAS$)$