SA-8(10)_hierarchical-trust

SA-8(10) Hierarchical Trust

Enhancement of: SA-8

High-Level Description

Family: System and Services Acquisition (SA) Framework: NIST SP 800-53 Rev 5

The principle of hierarchical trust for components builds on the principle of trusted components and states that the security dependencies in a system will form a partial ordering if they preserve the principle of trusted components. The partial ordering provides the basis for trustworthiness reasoning or an assurance case (assurance argument) when composing a secure system from heterogeneously trustworthy components. To analyze a system composed of heterogeneously trustworthy components for its trustworthiness, it is essential to eliminate circular dependencies with regard to the trustworthiness. If a more trustworthy component located in a lower layer of the system were to depend on a less trustworthy component in a higher layer, this would, in effect, put the components in the same "less trustworthy" equivalence class per the principle of trusted components. Trust relationships, or chains of trust, can have various manifestations. For example, the root certificate of a certificate hierarchy is the most trusted node in the hierarchy, whereas the leaves in the hierarchy may be the least trustworthy nodes. Another example occurs in a layered high-assurance system where the security kernel (including the hardware base), which is located at the lowest layer of the system, is the most trustworthy component. The principle of hierarchical trust, however, does not prohibit the use of overly trustworthy components. There may be cases in a system of low trustworthiness where it is reasonable to employ a highly trustworthy component rather than one that is less trustworthy (e.g., due to availability or other cost-benefit driver). For such a case, any dependency of the highly trustworthy component upon a less trustworthy component does not degrade the trustworthiness of the resulting low-trust system.

What to Check

• Verify SA-8(10) Hierarchical Trust is documented in SSP
• Confirm control is operating effectively
• Review evidence of continuous monitoring for SA-8(10)
• Verify enhancement builds upon base control SA-8

How to Test

Step 1: Review Documentation

Examine the System Security Plan (SSP) and related artifacts for SA-8(10) implementation details. Verify the organization has documented how this control is satisfied.

Step 2: Validate Implementation

# For cloud environments, use cloud-audit-mcp tools
# For on-premises, review system configurations directly

# Example: Check if account management policies exist
grep -r "account.management\|access.control" /etc/security/ 2>/dev/null

Step 3: Test Operating Effectiveness

Verify the control is actively functioning, not just documented. Check logs, configurations, and operational evidence.

Tools

Remediation Guide

Control Statement

Implement the security design principle of hierarchical trust in [organization-defined].

Implementation Guidance

The principle of hierarchical trust for components builds on the principle of trusted components and states that the security dependencies in a system will form a partial ordering if they preserve the principle of trusted components. The partial ordering provides the basis for trustworthiness reasoning or an assurance case (assurance argument) when composing a secure system from heterogeneously trustworthy components. To analyze a system composed of heterogeneously trustworthy components for its trustworthiness, it is essential to eliminate circular dependencies with regard to the trustworthiness. If a more trustworthy component located in a lower layer of the system were to depend on a less trustworthy component in a higher layer, this would, in effect, put the components in the same "less trustworthy" equivalence class per the principle of trusted components. Trust relationships, or chains of trust, can have various manifestations. For example, the root certificate of a certificate hierarchy is the most trusted node in the hierarchy, whereas the leaves in the hierarchy may be the least trustworthy nodes. Another example occurs in a layered high-assurance system where the security kernel (including the hardware base), which is located at the lowest layer of the system, is the most trustworthy component. The principle of hierarchical trust, however, does not prohibit the use of overly trustworthy components. There may be cases in a system of low trustworthiness where it is reasonable to employ a highly trustworthy component rather than one that is less trustworthy (e.g., due to availability or other cost-benefit driver). For such a case, any dependency of the highly trustworthy component upon a less trustworthy component does not degrade the trustworthiness of the resulting low-trust system.

Risk Assessment

CWE Categories

References

• NIST SP 800-53 Rev 5 - SA-8(10)
• NIST SP 800-53A Rev 5 (Assessment Procedures)
• NIST SP 800-53 Rev 5 Full Catalog

Checklist

• Control documented in SSP
• Implementation evidence collected
• Operating effectiveness validated
• Continuous monitoring in place
• Related controls (none) reviewed