Control statement
- a.Provide additional data origin authentication and integrity verification artifacts along with the authoritative name resolution data the system returns in response to external name/address resolution queries; and
- b.Provide the means to indicate the security status of child zones and (if the child supports secure resolution services) to enable verification of a chain of trust among parent and child domains, when operating as part of a distributed, hierarchical namespace.
Discussion
Providing authoritative source information enables external clients, including remote Internet clients, to obtain origin authentication and integrity verification assurances for the host/service name to network address resolution information obtained through the service. Systems that provide name and address resolution services include domain name system (DNS) servers. Additional artifacts include DNS Security Extensions (DNSSEC) digital signatures and cryptographic keys. Authoritative data includes DNS resource records. The means for indicating the security status of child zones include the use of delegation signer resource records in the DNS. Systems that use technologies other than the DNS to map between host and service names and network addresses provide other means to assure the authenticity and integrity of response data.
From control text to operational evidence
Use Secure Name/Address Resolution Service (Authoritative Source) as a testable risk decision. Translate the official statement into accountable people, repeatable processes, configured technology, and evidence that demonstrates the outcome over time. In this family, pay particular attention to secure architecture, boundary protection, communications protection, cryptography, and system isolation.
Implementation workflow
- Define the control boundary, responsible owner, inherited portions, and systems or processes in scope.
- Resolve each organization-defined parameter before declaring the control implemented.
- Document how the implementation satisfies every clause of the official control statement.
- Collect evidence as a normal byproduct of operation rather than only before an assessment.
- Review exceptions, changes, and monitoring results on a risk-based cadence.
Evidence examples
- network and trust-boundary diagrams
- firewall and gateway configurations
- cryptographic configuration and key records
- segmentation and isolation test results
Common failure patterns
- diagrams omit cloud and third-party paths
- encryption enabled without key governance
- flat trust zones allow unnecessary lateral movement
- boundary rules accumulate without owner review
Questions practitioners should ask
- What risk decision is this control intended to support in this system?
- Which parts are implemented locally, inherited, shared, or not applicable—and what evidence supports that decision?
- Do the documented narrative, deployed configuration, operating process, and collected evidence agree?
- What event or threshold requires the implementation to be reviewed or changed?
Assessment objectives and methods
Show the assessment objective
- SC-20a.
- SC-20a.[01]additional data origin authentication is provided along with the authoritative name resolution data that the system returns in response to external name/address resolution queries;
- SC-20a.[02]integrity verification artifacts are provided along with the authoritative name resolution data that the system returns in response to external name/address resolution queries;
- SC-20b.
- SC-20b.[01]the means to indicate the security status of child zones (and if the child supports secure resolution services) is provided when operating as part of a distributed, hierarchical namespace;
- SC-20b.[02]the means to enable verification of a chain of trust among parent and child domains when operating as part of a distributed, hierarchical namespace is provided.
Examine
- System and communications protection policy
- procedures addressing secure name/address resolution services (authoritative source)
- system design documentation
- system configuration settings and associated documentation
- system security plan
- other relevant documents or records
Interview
- System/network administrators
- organizational personnel with information security responsibilities
- organizational personnel with responsibilities for managing DNS
Test
- Mechanisms supporting and/or implementing secure name/address resolution services
Related controls
These relationships come from the official OSCAL catalog. They indicate useful dependencies or context, not automatic inheritance or equivalence.
Control enhancements
Enhancements add specificity, strength, or scope to the base control. Baseline badges show explicit selections in the official SP 800-53B OSCAL profiles.
SC-20(1) — Child Subspaces
This enhancement is marked withdrawn in the official OSCAL catalog. Related-control metadata below may identify where its intent was incorporated.
SC-20(2) — Data Origin and Integrity
Provide data origin and integrity protection artifacts for internal name/address resolution queries.
Official discussion
None.
Assessment objectives and methods
- SC-20(02)[01]data origin artifacts are provided for internal name/address resolution queries;
- SC-20(02)[02]integrity protection artifacts are provided for internal name/address resolution queries.
Examine
- System and communications protection policy
- procedures addressing secure name/address resolution services (authoritative source)
- system design documentation
- system configuration settings and associated documentation
- system audit records
- system security plan
- other relevant documents or records
Interview
- System/network administrators
- organizational personnel with information security responsibilities
- organizational personnel with responsibilities for managing DNS
Test
- Mechanisms supporting and/or implementing data origin and integrity protection for internal name/address resolution service queries
Authoritative sources
Bare Metal Cyber is an independent educational publisher and is not affiliated with or endorsed by NIST. Official control requirements and interpretations remain with NIST and the responsible authorizing organization.