The BIND 9.x server private key corresponding to the zone-signing key (ZSK) pair must be the only DNSSEC key kept on a name server that supports dynamic updates.

The private key in the ZSK key pair must be protected from unauthorized access. If possible, the private key should be stored offline (with respect to the internet-facing, DNSSEC-aware name server) in a physically secure, nonnetwork-accessible machine along with the zone file primary copy.

This strategy is not feasible in situations in which the DNSSEC-aware name server has to support dynamic updates. To support dynamic update transactions, the DNSSEC-aware name server (which usually is a primary authoritative name server) has to have both the zone file primary copy and the private key corresponding to the zone-signing key (ZSK-private) online to immediately update the signatures for the updated RRsets.

Failure to protect the private ZSK opens it to being maliciously obtained and opens the DNS zone to being populated with invalid data. The integrity of the DNS zone would be compromised, leading to a loss of trust whether a DNS response has originated from an authentic source, the response is complete and has not been tampered with during transit.