/ˌkeɪ-ɛs-ˈkeɪ/
n. “The master key that vouches for all zone signatures in DNSSEC.”
KSK, short for Key Signing Key, is a cryptographic key used in DNSSEC (Domain Name System Security Extensions) to sign the Zone Signing Keys (ZSKs) of a DNS zone. Unlike the ZSK, which signs individual DNS records, the KSK signs the keys themselves, creating a trust chain that allows resolvers to verify the authenticity of the DNS data.
Key characteristics of a KSK include:
- Signs Keys, Not Records: KSK signs the ZSKs, which in turn sign the DNS records within a zone.
- Longer Lifespan: KSKs are typically rotated less frequently than ZSKs to maintain stability in the DNSSEC trust chain.
- Establishes Trust: By signing ZSKs, the KSK allows clients and resolvers to verify that the zone’s DNS records are authentic.
- Part of the DNSSEC Hierarchy: Works alongside ZSK to form a chain of trust that secures DNS responses from tampering or forgery.
Conceptually, the KSK is like a master notary that certifies the signatures of the ZSK, which then “sign” the actual DNS records. This two-tier system ensures that both the keys and the data they sign can be trusted.
In essence, KSK is a fundamental building block of DNSSEC security, providing the top-level assurance that DNS information is authentic, untampered, and reliable for clients and resolvers.