CyberGlossary

Network Security

DNSSEC

Also known as: DNS Security Extensions

Definition

A set of DNS extensions that cryptographically sign zone data so resolvers can verify the authenticity and integrity of DNS responses.

DNSSEC (Domain Name System Security Extensions) adds public-key signatures to DNS records, allowing a validating resolver to confirm that an answer truly came from the authoritative zone and has not been altered in transit. Each zone publishes a DNSKEY and signs its resource records with RRSIG records, while DS records in the parent zone create a chain of trust up to the signed root. DNSSEC defends against DNS cache poisoning, on-path tampering, and spoofed answers from rogue resolvers. It does not encrypt queries — confidentiality requires DoH or DoT — but it is a critical building block for trustworthy name resolution and downstream protocols like DANE.

Examples

  • A validating resolver rejects a forged response for bank.example because the RRSIG does not verify against the published DNSKEY.
  • A registry rolls its ZSK and publishes new DS records at the parent to maintain the chain of trust.

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