Control statement
- a.Provide a [Organization-defined: sc-11_odp.01] isolated trusted communications path for communications between the user and the trusted components of the system; and
- b.Permit users to invoke the trusted communications path for communications between the user and the following security functions of the system, including at a minimum, authentication and re-authentication: [Organization-defined: security functions].
Discussion
Trusted paths are mechanisms by which users can communicate (using input devices such as keyboards) directly with the security functions of systems with the requisite assurance to support security policies. Trusted path mechanisms can only be activated by users or the security functions of organizational systems. User responses that occur via trusted paths are protected from modification by and disclosure to untrusted applications. Organizations employ trusted paths for trustworthy, high-assurance connections between security functions of systems and users, including during system logons. The original implementations of trusted paths employed an out-of-band signal to initiate the path, such as using the <BREAK> key, which does not transmit characters that can be spoofed. In later implementations, a key combination that could not be hijacked was used (e.g., the <CTRL> + <ALT> + <DEL> keys). Such key combinations, however, are platform-specific and may not provide a trusted path implementation in every case. The enforcement of trusted communications paths is provided by a specific implementation that meets the reference monitor concept.
Organization-defined parameters
These values must be resolved through the organization’s tailoring and governance process. Bracketed parameter references in the control text identify where a decision is required.
From control text to operational evidence
Use Trusted Path 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-11a.a [Organization-defined: sc-11_odp.01] isolated trusted communication path is provided for communications between the user and the trusted components of the system;
- SC-11b.users are permitted to invoke the trusted communication path for communications between the user and the [Organization-defined: security functions] of the system, including authentication and re-authentication, at a minimum.
Examine
- System and communications protection policy
- procedures addressing trusted communication paths
- security plan
- system design documentation
- system configuration settings and associated documentation
- assessment results from independent, testing organizations
- system audit records
- system security plan
- other relevant documents or records
Interview
- System/network administrators
- organizational personnel with information security responsibilities
- system developer
Test
- Mechanisms supporting and/or implementing trusted communication paths
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-11(1) — Irrefutable Communications Path
- (a)Provide a trusted communications path that is irrefutably distinguishable from other communications paths; and
- (b)Initiate the trusted communications path for communications between the [Organization-defined: security functions] of the system and the user.
Official discussion
An irrefutable communications path permits the system to initiate a trusted path, which necessitates that the user can unmistakably recognize the source of the communication as a trusted system component. For example, the trusted path may appear in an area of the display that other applications cannot access or be based on the presence of an identifier that cannot be spoofed.
Organization-defined parameters (1)
Assessment objectives and methods
- SC-11(01)(a)a trusted communication path that is irrefutably distinguishable from other communication paths is provided;
- SC-11(01)(b)the trusted communication path for communications between the [Organization-defined: security functions] of the system and the user is initiated.
Examine
- System and communications protection policy
- procedures addressing trusted communication paths
- security plan
- system design documentation
- system configuration settings and associated documentation
- assessment results from independent, testing organizations
- system audit records
- system security plan
- other relevant documents or records
Interview
- System/network administrators
- organizational personnel with information security responsibilities
- system developer
Test
- Mechanisms supporting and/or implementing trusted communication paths
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.