Encrypt CUI On Mobile
Encrypt CUI on mobile devices and mobile computing platforms.
What an assessor scores, the objectives
AC.L2-3.1.19 is met only when every one of these 2 objectives, from NIST SP 800-171A, is satisfied. A single missed objective makes the whole requirement not met.
- a.mobile devices and mobile computing platforms that process, store, or transmit CUI are identified
- b.encryption is employed to protect CUI on identified mobile devices and mobile computing platforms
How a C3PAO checks it
NIST SP 800-171A defines three assessment methods. For AC.L2-3.1.19, an assessor uses these:
Access control policy; procedures addressing access control for mobile devices; system design documentation; system configuration settings and associated documentation; encryption mechanisms and associated configuration documentation; system security plan; system audit logs and records; other relevant documents or records
Personnel with access control responsibilities for mobile devices; system or network administrators; personnel with information security responsibilities
Encryption mechanisms protecting confidentiality of information on mobile devices
What it means, in context
Organizations can employ full -device encryption or container -based encryption to protect the confidentiality of CUI on mobile devices and computing platforms . Container-based encryption provides a more fine-grained approach to the encryption of data and information including encrypting selected data structures such as files, records, or fields.
Ensure CUI is encrypted on all mobile devices and mobile computing platforms that process, store, or transmit CUI including smartphones, tablets, and e-readers. Because the use of cryptography in this requirement is to protect the confidentiality of CUI , the cryptography used must meet the criteria specified in requirement SC.L2-3.13.11. This requirement, AC.L2 -3.1.19, specifies that CUI be encrypted on mobile devices and extends three other CUI protection requirements (MP.L2-3.8.1, MP.L2-3.8.2, and SC.L2 - 3.13.16): • MP.L2-3.8.1 requires that media containing CUI be protected. • MP.L2-3.8.2 limits access to CUI to authorized users. • Finally, SC.L2-3.13.16 requires confidentiality of CUI at rest. This requirement, AC.L2-3.1.19, also leverages SC.L2-3.13.11, which specifies that the algorithms used must be FIPS -validated cryptography, and SC.L2-3.13.10, which specifies that any cryptographic keys in use must be protected. Example You are in charge of mobile device security for a company that processes CUI. You configure all laptops to use the full- disk encryption technology built into the operating system. This approach is FIPS-validated and encrypts all files, folders, and volumes. Phones and tablets pose a greater technical challenge with their wide range of manufacturers and operating systems. You select a proprietary mobile device management (MDM) solution to enforce FIPS-validated encryption on those devices [a,b]. Potential Assessment Considerations • Is a list maintained of mobile devices and mobile computing platforms that are permitted to process, store, or transmit CUI [a]? • Is CUI encrypted on mobile devices using FIPS-validated algorithms [b]? KEY REFERENCE • NIST SP 800-171 Rev. 2 3.1.19
What passing evidence looks like
Proof of encryption on every mobile device and platform that can hold CUI: the Intune compliance policy requiring encryption plus a compliant device report, or per device encryption screenshots.
Common ways contractors fail AC.L2-3.1.19
- !Laptops that travel count as mobile computing platforms. BitLocker on every laptop, not just phones.
The step by step walkthrough for Microsoft 365 GCC High, Google Workspace, and on premises setups, plus the exact evidence to capture, lives inside the Level 2 Accelerator.
Prove AC.L2-3.1.19, and the other 109
The Level 2 Accelerator walks all 110 requirements with you, generates your SSP, POA&M, and Audit Room from real evidence, includes the full Level 1 platform, and puts a credentialed officer alongside you for 180 days. Filed in 180 days, or we work free until you are.
No credit card. Phase 2 begins Nov 10, 2026, when applicable DoD solicitations start requiring a current Level 2 status to win the award.
AC.L2-3.1.19 questions, answered
How many points is CMMC requirement AC.L2-3.1.19 worth?+
AC.L2-3.1.19 is worth 3 points in the CMMC Level 2 score under 32 CFR 170.24. If it is not met, you lose 3 from your total of 110.
Can AC.L2-3.1.19 be placed on a POA&M?+
No. AC.L2-3.1.19 must be fully met before you can file. It cannot be deferred to a POA&M, so it is a gate on your assessment.
What family does AC.L2-3.1.19 belong to?+
AC.L2-3.1.19 is in the Access Control (AC) family, one of the 14 families of NIST SP 800-171 that make up CMMC Level 2.