NIST 800-171 3.1.19 (AC.L2-3.1.19): Encrypt CUI on Mobile

Encrypt CUI on mobile devices and mobile computing platforms.

NIST SP 800-171 Rev. 2, requirement 3.1.19

CMMC Level 2 practice AC.L2-3.1.19Published 2026-11-11

What 3.1.19 means in practice

Any phone, tablet or laptop that carries CUI encrypts it, either the whole device or a managed container that holds the CUI. Device management requires the encryption and reports any device that lacks it.

SPRS points and the CMMC POA&M

CMMC Level 2 practice: AC.L2-3.1.19
SPRS points: 3 points. When it is not met, the DoD Assessment Methodology subtracts 3 from the score of 110.
CMMC POA&M: Not allowed. It is worth 3 points, and 32 CFR 170.21(a)(2)(ii) admits only requirements worth 1 point, with one exception: 3.13.11 when encryption is used but not FIPS validated.

Sources: NIST SP 800-171 DoD Assessment Methodology, version 1.2.1 (June 24, 2020), Annex A; 32 CFR 170.21, Plan of Action and Milestones requirements.

What an assessor checks for 3.1.19

NIST SP 800-171A gives 2 determination statements for 3.1.19, each found satisfied or other than satisfied. Determine if:

3.1.19[a] mobile devices and mobile computing platforms that process, store, or transmit CUI are identified.
3.1.19[b] encryption is employed to protect CUI on identified mobile devices and mobile computing platforms.

NIST SP 800-171A (June 2018), assessment objectives for 3.1.19

Evidence that shows 3.1.19 is met

Device management compliance rules that require storage encryption.
An encryption status report for the mobile devices and laptops that hold CUI.
Container or app protection settings, where container encryption is used instead.

How PolicyCortex gathers the evidence

PolicyCortex reads this evidence with the collectors below, read only, and grades 3.1.19 from it. Each line says what the product checks.

Microsoft Intune: Compliance policies · Device configurations. Checks that every mobile device and laptop Intune manages is required to encrypt its storage.

Related pages

Calculator: SPRS score calculator: mark 3.1.19 and the other 109 requirements and see the score.
Sample package: Sample package: an SSP, a POA&M and an evidence chain the product generated from demonstration data.
Family: All 22 Access Control requirements (3.1).
Previous: 3.1.18: Mobile Device Connection
Next: 3.1.20: External Connections
All requirements: All 110 NIST SP 800-171 requirements, by family.

Related records

Guides and articles describe the work. The evidence that work produces is described in three proof pages, the architecture page, and the two pages on authorization.

proof.state: Proof of State. What the environment was, as of a date someone else picks: point-in-time records, content hashed and chained.
proof.change: Proof of Change. Who or what altered the environment, under what authority, with before and after state hashes.
proof.agency: Proof of Agency. What a machine was permitted to do before it acted, what it did, and what would have stopped it.
architecture: Architecture. How the chain is built and where the evidence is stored in each delivery mode.
authorization: Continuous ATO. How an authorizing official's decision is recorded with its package, and how the authorized system is checked against it every hour.
baseline: NIST SP 800-53. The Low, Moderate and High baselines as evidence, with the SSP, SAR and POA&M generated from one record.