--- title: "NIST 800-171 3.13.8 (SC.L2-3.13.8): Encryption in Transit" description: "NIST SP 800-171 3.13.8 Encryption in Transit: 3 SPRS points, not allowed on a CMMC POA&M. The text, what assessors check and the evidence." url: https://policycortex.com/nist-800-171/system-and-communications-protection/3.13.8 sealed: 2026-11-11 amended: 2026-11-11 register: nist-800-171/system-and-communications-protection/3.13.8 records: 7 digest: sha3:fc0895e726dd0cf915cb675ef713e8527ca4e37fd1c6155231c135928ebad5ee --- # NIST 800-171 3.13.8 (SC.L2-3.13.8): Encryption in Transit NIST 800-171 / System and Communications Protection / 3.13.8 "Implement cryptographic mechanisms to prevent unauthorized disclosure of CUI during transmission unless otherwise protected by alternative physical safeguards." ([NIST SP 800-171 Rev. 2, requirement 3.13.8](https://doi.org/10.6028/NIST.SP.800-171r2)) CMMC Level 2 practice SC.L2-3.13.8. ## What 3.13.8 means in practice CUI moving across any network is encrypted, unless it is physically protected some other way, such as a cable that runs entirely inside a controlled area. That covers web traffic, email, file transfers and links between sites, and because the encryption protects CUI it should be FIPS validated. ## SPRS points and the CMMC POA&M - **CMMC Level 2 practice**: SC.L2-3.13.8 - **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. - **Scoring note**: Encryption is not required over a common carrier's MPLS service: its separation counts as protection. Sources: [NIST SP 800-171 DoD Assessment Methodology, version 1.2.1 (June 24, 2020), Annex A](https://www.acq.osd.mil/asda/dpc/cp/cyber/docs/safeguarding/NIST-SP-800-171-Assessment-Methodology-Version-1.2.1-6.24.2020.pdf); [32 CFR 170.21, Plan of Action and Milestones requirements](https://www.ecfr.gov/current/title-32/section-170.21). ## What an assessor checks for 3.13.8 NIST SP 800-171A gives 3 determination statements for 3.13.8, each found satisfied or other than satisfied. Determine if: - 3.13.8[a] cryptographic mechanisms intended to prevent unauthorized disclosure of CUI are identified. - 3.13.8[b] alternative physical safeguards intended to prevent unauthorized disclosure of CUI are identified. - 3.13.8[c] either cryptographic mechanisms or alternative physical safeguards are implemented to prevent unauthorized disclosure of CUI during transmission. [NIST SP 800-171A (June 2018), assessment objectives for 3.13.8](https://doi.org/10.6028/NIST.SP.800-171A) ## Evidence that shows 3.13.8 is met - TLS settings for web servers, applications and email. - VPN or link encryption between sites. - An inventory of the paths CUI travels, with the protection on each. ## How PolicyCortex gathers the evidence PolicyCortex reads this evidence with the collectors below, read only, and grades 3.13.8 from it. Each line says what the product checks. - **Azure Storage: Storage accounts.** Checks that every Azure Storage account accepts only HTTPS. - **Azure App Service: App settings.** Checks that every App Service accepts only HTTPS and requires TLS 1.2 or later. - **AWS: S3 buckets · Data stores · Load balancers, API Gateway, CloudFront and Lambda.** Checks that S3 bucket policies deny insecure transport, that Redshift and ElastiCache encrypt connections, that load balancers listen only on HTTPS or TLS with ACM certificates and redirect HTTP, and that API Gateway stages use a client certificate. ## Related pages - **Calculator**: [SPRS score calculator: mark 3.13.8 and the other 109 requirements and see the score.](https://policycortex.com/sprs-score-calculator#family-SC) - **Sample package**: [Sample package: an SSP, a POA&M and an evidence chain the product generated from demonstration data.](https://policycortex.com/sample-package) - **Family**: [All 16 System and Communications Protection requirements (3.13).](https://policycortex.com/nist-800-171/system-and-communications-protection) - **Previous**: [3.13.7: Split Tunneling](https://policycortex.com/nist-800-171/system-and-communications-protection/3.13.7) - **Next**: [3.13.9: Connection Termination](https://policycortex.com/nist-800-171/system-and-communications-protection/3.13.9) - **All requirements**: [All 110 NIST SP 800-171 requirements, by family.](https://policycortex.com/nist-800-171) Meet the requirement once. Keep the evidence current. [Request Access](https://app.policycortex.com/auth?mode=request-access) · [Book a call](https://policycortex.com/book) ## Register colophon | Seq | Label | SHA3-256 | Prev | |---|---|---|---| | REC 0000 | REQUIREMENT | bfcfc362bf86 | 622730875801 | | REC 0001 | MEANING | 5503c8c03bba | bfcfc362bf86 | | REC 0002 | POINTS AND POA&M | 4d7329aa2d0a | 5503c8c03bba | | REC 0003 | ASSESSMENT OBJECTIVES | 9f39096b6bdc | 4d7329aa2d0a | | REC 0004 | EVIDENCE | 55db5269e5a0 | 9f39096b6bdc | | REC 0005 | COLLECTORS | fd9263cc3505 | 55db5269e5a0 | | REC 0006 | RELATED | fc0895e726dd | fd9263cc3505 | Head sha3:fc0895e726dd0cf915cb675ef713e8527ca4e37fd1c6155231c135928ebad5ee. Each digest is SHA3-256 over the previous digest, the register key, the record label, and the record copy; a second party can recompute it from this document.