How does TSIG authenticate name servers in order to perform secured zone transfers?
A.
Both servers mutually verify their X509 certificates.
B.
Both servers use a secret key that is shared between the servers.
C.
Both servers verify appropriate DANE records for the labels of the NS records used to delegate the transferred zone.
D.
Both servers use DNSSEC to mutually verify that they are authoritative for the transferred zone.
Explanation:
http://www.cyberciti.biz/faq/unix-linux-bind-named-configuring-tsig/