SC-40(1): Electromagnetic Interference

SC-40(1): electromagnetic interference requirement means you must implement cryptographic mechanisms that maintain your defined level of protection against intentional electromagnetic interference, and you must be able to prove it with system-specific evidence. Operationalize it by defining the protection objective, scoping impacted systems, selecting approved crypto, and documenting configuration, testing, and ownership. ¹

Key takeaways:

• Define your organization’s protection objective first, then engineer crypto and deployment to meet it. ¹
• Scope matters: prioritize mission-critical systems and high-consequence environments where intentional EMI is plausible. ²
• Evidence wins audits: mapping to an owner, procedure, and recurring artifacts is a minimum operating standard. ¹

SC-40(1) is easy to misread as a facilities shielding requirement. It is not written that way. The enhancement specifically calls for cryptographic mechanisms that achieve an organization-defined level of protection against the effects of intentional electromagnetic interference. ¹

For a CCO, GRC lead, or system owner, the operational challenge is twofold: (1) translate “organization-defined protection” into a concrete, testable objective for each in-scope system, and (2) show assessors that the cryptography you deployed, and how you deployed it, actually protects confidentiality and integrity (and where applicable availability) even when interference is intentional. ²

This page gives requirement-level implementation guidance you can assign today: who owns the control, what decisions must be made, what to build or configure, and what evidence to retain. If you already run a NIST-aligned program, treat SC-40(1) as a targeted hardening and assurance task for high-risk environments (field operations, industrial sites, sensitive facilities, or locations where a motivated adversary could attempt disruption or data extraction). ²

Regulatory text

Requirement (verbatim excerpt): “Implement cryptographic mechanisms that achieve {{ insert: param, sc-40.01_odp }} against the effects of intentional electromagnetic interference.” ¹

What the operator must do:

1. Define the organization-defined parameter (the “{{ insert: param, sc-40.01_odp }}” portion) as a measurable protection objective for the system or system class. ¹
2. Implement cryptographic mechanisms that meet that objective under intentional EMI conditions, not only under normal operating conditions. ¹
3. Demonstrate through design artifacts, configurations, and testing/assurance evidence that the objective is met for in-scope components and data flows. ²

Plain-English interpretation

You must assume an attacker could intentionally interfere with electronics (disrupting signals, inducing faults, or causing errors) and you must use cryptography in a way that still protects the system according to your defined objective. Practically, this usually means robust cryptographic protections for data in transit and at rest, strong integrity protection (e.g., authenticated encryption, digital signatures, message authentication), key management that resists corruption, and implementation choices that fail safely under error conditions. ¹

Who it applies to

Entities:

• Federal information systems and organizations implementing NIST SP 800-53 controls. ²
• Contractors and service providers handling federal data where 800-53 controls are flowed down contractually (common in agency ATO/FedRAMP-aligned environments). ²

Operational contexts where assessors care most:

• Systems supporting mission-critical operations where disruption has real consequences (command-and-control, emergency response, critical manufacturing).
• Systems operating in exposed or hostile physical environments (field sites, shared facilities, public-facing locations).
• Environments with sensitive processing where adversaries may attempt side-channel or fault-injection style outcomes via interference. ²

What you actually need to do (step-by-step)

Step 1: Set the “organization-defined protection” objective (make it testable)

Create a short SC-40(1) control statement with:

• Scope: systems, components, and data flows covered (include third-party hosted components if they process your federal data).
• Protection goal: what must remain true under intentional EMI (e.g., “confidentiality and integrity of protected data remains intact; cryptographic operations fail closed; keys are not exposed; tamper/fault events are detected and logged”).
• Assurance method: how you will demonstrate it (test approach, vendor attestations, design review criteria). ¹

Practical tip: write the objective so an assessor can answer “met / not met” without debating intent.

Step 2: Identify where cryptography is relied on for safety and trust

Build or update a simple inventory view:

• Encryption points for data in transit (service-to-service, admin access, API gateways, remote management).
• Encryption points for data at rest (databases, object storage, endpoints, backup media).
• Integrity mechanisms (signing, HMACs, AEAD modes, code signing, boot integrity).
• Key management path (HSM/KMS, key rotation, backup/restore of keys, separation of duties). ²

Deliverable: a one-page “crypto boundary and key flow” diagram per high-impact system.

Step 3: Select and standardize “approved crypto” patterns for EMI-relevant threats

SC-40(1) does not list algorithms. Your job is to standardize cryptographic mechanisms that (a) are approved in your environment and (b) provide confidentiality and integrity even if interference causes transmission errors or system instability. ¹

Implementation patterns most teams adopt:

• Authenticated encryption for data in transit and sensitive payloads, so tampering or corruption is detected rather than silently accepted.
• Integrity checks for software and configuration (signed artifacts, verified boot, signed container images).
• Key protection via centralized KMS/HSM, strict access control, and audit logging around key use and administrative actions.
• Fail-safe handling: if crypto checks fail due to corruption or faults, the system denies access, rejects messages, and logs the event rather than continuing in a degraded insecure mode.

Document these as “SC-40(1) crypto patterns” your engineers can reuse.

Step 4: Engineer for “fail closed” behavior under interference conditions

Intentional EMI can look like random faults, corrupted packets, intermittent hardware errors, or timeouts. Your crypto implementation must not turn those faults into:

• plaintext fallbacks,
• disabled certificate validation,
• bypassed signature checks,
• hard-coded keys or “temporary” debug settings. ²

Controls to implement:

• Enforce TLS settings centrally; block weak cipher suites and certificate bypass flags in production.
• Treat integrity failures as security events (SIEM alerting, incident workflow).
• Protect key material from being written to logs or crash dumps.
• Require secure defaults in client libraries and internal SDKs.

Step 5: Validate with assurance evidence (don’t rely on “we use TLS”)

Assessors commonly reject generic statements. Build targeted validation:

• Configuration evidence: actual settings from endpoints, gateways, KMS policies, and code signing pipelines.
• Negative tests: demonstrate corrupted payloads fail integrity checks and generate logs/tickets.
• Resilience checks: show that intermittent communication failures do not trigger insecure fallback behavior.
• Third-party attestations: where cryptographic modules are provided as a service, collect provider documentation and map it to your objective. ²

If you track controls in Daydream, set SC-40(1) up with a named owner, a written procedure, and recurring evidence tasks so you collect proof continuously instead of scrambling during an ATO or assessment. ¹

Step 6: Operationalize ownership and change control

Make SC-40(1) survivable through change:

• Assign a control owner (often Security Architecture, Crypto Engineering, or Platform Security).
• Tie relevant changes to review gates: certificate policy changes, KMS/HSM changes, TLS termination changes, signing pipeline changes.
• Add release checks: “no insecure crypto fallback,” “certificate validation enforced,” “integrity verification required.” ²

Required evidence and artifacts to retain

Keep artifacts system-specific and assessment-ready:

Artifact	What “good” looks like	Owner
SC-40(1) control statement with organization-defined objective	Clear, testable, scoped to system boundary	GRC + System Owner
Crypto architecture diagram	Data flows, trust boundaries, key lifecycle	Security Architecture
Crypto configuration exports	TLS configs, KMS key policies, signing settings	Platform/Cloud Ops
Test evidence	Integrity-failure tests, “fail closed” behavior, logs generated	QA/Sec Eng
Change records	Approvals for crypto-related changes, exceptions with expiry	Change Mgmt
Third-party documentation	Provider crypto/KMS/HSM docs mapped to your objective	TPDD/Vendor Mgmt

Minimum expectation for audit readiness: mapping SC-40(1) to an owner, procedure, and recurring evidence artifacts. ¹

Common exam/audit questions and hangups

Assessors tend to press on these points:

• “What is your organization-defined protection for SC-40(1)?” If you cannot state it plainly, you will lose time in the exam. ¹
• “Show me where this is implemented.” They will want system configs and diagrams, not policy prose.
• “How do you know interference won’t cause insecure fallback?” Bring negative tests and secure-default evidence.
• “Which cryptographic mechanisms are in scope?” If you only cite “TLS” without identifying termination points, ciphers, cert validation, and key storage, expect follow-ups.
• “What about third parties?” If a cloud service terminates TLS or manages keys, you still need mapped evidence and accountability. ²

Frequent implementation mistakes and how to avoid them

1. Mistake: Treating SC-40(1) as a facilities-only EMI shielding project.
   Fix: Anchor the work in cryptography and system behavior under fault conditions; coordinate with physical security only where your risk assessment calls for it. ¹

2. Mistake: No “organization-defined” parameter documented.
   Fix: Publish a system-class objective and reference it in SSP/control narratives and engineering standards. ¹

3. Mistake: Relying on vendor brochures instead of your own configs and tests.
   Fix: Collect configs, run negative tests, and document results; treat third-party docs as supporting evidence, not primary evidence. ²

4. Mistake: Hidden insecure fallback in libraries or proxies.
   Fix: standardize approved libraries, set policy-as-code guardrails, and add build-time checks for forbidden settings.

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for SC-40(1). The practical risk is assessment failure or delayed authorization because you cannot prove the organization-defined protection objective is implemented and operating, especially in systems with higher impact or higher threat exposure. ¹

Operationally, intentional EMI is a “high-consequence, low-frequency” scenario. Treat it as an assurance problem: integrity, key protection, and secure failure modes under abnormal conditions. ²

A practical 30/60/90-day execution plan

30 days: Define and scope

• Name a control owner and backup owner for SC-40(1). ¹
• Write the organization-defined protection objective for each in-scope system class and get sign-off from Security Architecture and the system owner. ¹
• Create the crypto boundary diagram for the highest-risk system.
• Stand up an evidence register (what you will collect, from where, how often).

60 days: Implement and standardize

• Publish standard crypto patterns (AEAD for sensitive payloads, signing standards, key management rules) and integrate them into engineering guidance. ²
• Add guardrails: configuration baselines for TLS endpoints and certificate validation; logging requirements for integrity failures.
• Start collecting recurring evidence automatically where possible (config exports, key policy snapshots, CI/CD signing logs). Daydream is a good fit for assigning owners and scheduling recurring artifacts per control. ¹

90 days: Prove it works and make it durable

• Execute negative tests in a controlled environment: corrupt payloads, failed signature checks, invalid certificates; capture logs and tickets as evidence.
• Run a tabletop exercise focused on interference-like failure modes (timeouts, corrupted messages) and confirm the system fails closed.
• Close gaps found in testing; document exceptions with compensating controls and expiry dates.

Frequently Asked Questions

What counts as “intentional electromagnetic interference” for SC-40(1)?

Treat it as an adversary-driven condition that can induce faults, corruption, or disruption in electronics and communications. Your implementation focus is proving cryptography still protects confidentiality and integrity to your defined objective. ¹

Do we need TEMPEST shielding or specialized facilities work to satisfy SC-40(1)?

SC-40(1) is written as a cryptographic mechanism requirement, not a shielding mandate. If your threat model calls for facilities controls, document them separately, but don’t substitute them for crypto evidence. ¹

How do we define the “organization-defined protection” parameter without overcommitting?

Define it per system class and make it testable: what must remain protected, what “fail closed” means, and what evidence proves it. Keep the objective aligned to your system impact and operating environment. ¹

What evidence is most convincing to auditors for SC-40(1)?

Configuration outputs (TLS, KMS/HSM policies, signing settings) plus negative tests that show corrupted or tampered inputs are rejected and logged. Pair this with a clear owner and written procedure. ²

How does SC-40(1) apply to cloud services where the provider manages keys?

You remain responsible for mapping the control to your environment: define the objective, document shared responsibility, retain provider documentation, and collect your own tenant-side configs and logs. ²

Can we mark SC-40(1) “inherited” from a third party?

Sometimes parts are inherited, but you still need system-specific documentation showing what is inherited, what you configure, and how you validate behavior under fault conditions. Treat inheritance as a scope tool, not an evidence substitute. ²

Footnotes

1. NIST SP 800-53 Rev. 5 OSCAL JSON

2. NIST SP 800-53 Rev. 5