---
title: "NIST 800-171 3.5.4 (IA.L2-3.5.4): Replay Resistance"
description: "NIST SP 800-171 3.5.4 Replay Resistance: 1 SPRS point, allowed on a CMMC POA&M. The text, what assessors check and the evidence."
url: https://policycortex.com/nist-800-171/identification-and-authentication/3.5.4
sealed: 2026-11-11
amended: 2026-11-11
register: nist-800-171/identification-and-authentication/3.5.4
records: 7
digest: sha3:40d4b1f50decd6da25a8d3aad3b158962b6ee6ad9a6c16a3f897ded9ac1aa39b
---

# NIST 800-171 3.5.4 (IA.L2-3.5.4): Replay Resistance

NIST 800-171 / Identification and Authentication / 3.5.4

"Employ replay-resistant authentication mechanisms for network access to privileged and non-privileged accounts." ([NIST SP 800-171 Rev. 2, requirement 3.5.4](https://doi.org/10.6028/NIST.SP.800-171r2))

CMMC Level 2 practice IA.L2-3.5.4.

## What 3.5.4 means in practice

A captured sign-in must not be reusable by whoever captured it. Authentication built on one-time codes, challenge and response, or cryptographic tokens (such as Kerberos, FIDO2 security keys or authenticator apps) resists replay; protocols that send a reusable password or hash, like basic authentication, do not.

## SPRS points and the CMMC POA&M

- **CMMC Level 2 practice**: IA.L2-3.5.4
- **SPRS points**: 1 point. When it is not met, the DoD Assessment Methodology subtracts 1 from the score of 110.
- **CMMC POA&M**: Allowed. It is worth 1 point, and 32 CFR 170.21(a)(2)(ii) admits requirements worth 1 point. Conditional status also needs a score of at least 88, and the item must be closed within 180 days.

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 3.5.4

NIST SP 800-171A gives one determination statement for 3.5.4.

- Determine if replay-resistant authentication mechanisms are implemented for network account access to privileged and non-privileged accounts.

[NIST SP 800-171A (June 2018), assessment objectives for 3.5.4](https://doi.org/10.6028/NIST.SP.800-171A)

## Evidence that shows 3.5.4 is met

- The authentication protocols allowed for network access, and the legacy ones disabled.
- Identity provider settings for the factors in use, such as FIDO2 security keys or authenticator apps.
- VPN and network device authentication settings.

## How PolicyCortex gathers the evidence

PolicyCortex reads this evidence with the collectors below, read only, and grades 3.5.4 from it. Each line says what the product checks.

- **Microsoft Entra ID: Conditional Access.** Checks that Conditional Access requires a replay-resistant factor for network sign-ins by every user and by privileged accounts.
- **Microsoft Entra ID: Authentication methods.** Reads the Microsoft Entra authentication methods policy and reports whether FIDO2 security keys and certificate-based authentication are turned on.
- **Okta: Policies.** Checks that Okta sign-ins require a replay-resistant second factor.

## Related pages

- **Calculator**: [SPRS score calculator: mark 3.5.4 and the other 109 requirements and see the score.](https://policycortex.com/sprs-score-calculator#family-IA)
- **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 11 Identification and Authentication requirements (3.5).](https://policycortex.com/nist-800-171/identification-and-authentication)
- **Previous**: [3.5.3: Multifactor Authentication](https://policycortex.com/nist-800-171/identification-and-authentication/3.5.3)
- **Next**: [3.5.5: Identifier Reuse](https://policycortex.com/nist-800-171/identification-and-authentication/3.5.5)
- **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 | 87df81c0b4d0 | ab76458c6342 |
| REC 0001 | MEANING | 232bc5fb6630 | 87df81c0b4d0 |
| REC 0002 | POINTS AND POA&M | c45e29ed21c5 | 232bc5fb6630 |
| REC 0003 | ASSESSMENT OBJECTIVES | 002ccb198ad3 | c45e29ed21c5 |
| REC 0004 | EVIDENCE | dc786ff16070 | 002ccb198ad3 |
| REC 0005 | COLLECTORS | ec30975247eb | dc786ff16070 |
| REC 0006 | RELATED | 40d4b1f50dec | ec30975247eb |

Head sha3:40d4b1f50decd6da25a8d3aad3b158962b6ee6ad9a6c16a3f897ded9ac1aa39b. 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.