The private key corresponding to the ZSK, stored on name servers accepting dynamic updates, must have appropriate directory/file-level access control list-based or cryptography-based protections.

The private keys in the KSK and ZSK key pairs must be protected from unauthorized access. If possible, the private keys should be stored off-line (with respect to the Internet-facing, DNSSEC-aware name server) in a physically secure, non-network-accessible machine along with the zone file master 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 master copy and the private key corresponding to the zone-signing key (ZSK-private) online to immediately update the signatures for the updated RRsets. The private key corresponding to the key-signing key (KSK-private) can still be kept off-line.