3.5.4Use replay-resistant authentication

A captured login cannot simply be replayed to get in.

The requirement, verbatim

NIST SP 800-171 Rev. 2 · 3.5.4
Employ replay-resistant authentication mechanisms for network access to privileged and non-privileged accounts.

Requirement 3.5.4, practice name in the CMMC assessment guide: Replay-Resistant Authentication.

NIST's discussion

Authentication processes resist replay attacks if it is impractical to successfully authenticate by recording or replaying previous authentication messages. Replay-resistant techniques include protocols that use nonces or challenges such as time synchronous or challenge-response one-time authenticators.

NIST SP 800-63-3 provides guidance on digital identities.

NIST SP 800-171 Rev. 2, discussion under 3.5.4. Whitespace normalised; wording unchanged.

Assessment objectives

An assessor decides each of these separately. The requirement is met only when every objective is.

[a] replay-resistant authentication mechanisms are implemented for network access to privileged accounts
[b] replay-resistant authentication mechanisms are implemented for network access to non-privileged accounts

NIST SP 800-171A, determination statements for 3.5.4.

For assessors: examine, interview, test

NIST SP 800-171A names what an assessor may examine, whom they may interview, and what they may test for this requirement. Assessors select from these lists; they are not a checklist of everything you must produce.

Examine

Identification and authentication policy
procedures addressing user identification and authentication
system security plan
system design documentation
system configuration settings and associated documentation
system audit logs and records
list of privileged system accounts
other relevant documents or records

Interview

Personnel with system operations responsibilities
personnel with account management responsibilities
personnel with information security responsibilities
system or network administrators
system developers

Test

Mechanisms supporting or implementing identification and authentication capability or replay resistant authentication mechanisms

NIST SP 800-171A, potential assessment methods and objects for 3.5.4.

Evidence

No evidence examples are published for this requirement yet. The objectives above are what an assessor checks; evidence is whatever shows each one is true in your environment, dated and kept with your system security plan.

Scoring weight

Worth 1 point. Not meeting this requirement subtracts 1 from your 110-point SPRS score.

DoD NIST SP 800-171 Assessment Methodology v1.2.1 weighting, as carried in the Bedrock scoring table. The score starts at 110 and subtracts the weight of every requirement not met.

In Rev. 3

Rev. 2 is what your contract requires today. A standing DoD class deviation keeps Rev. 2 in force; NIST has published Rev. 3, but it is not adopted for contracts. In Rev. 3 this requirement is no significant change: 03.05.04 Replay-Resistant Authentication.

See the Rev. 2 and Rev. 3 wording word by word, or start with the status page.

Where this page's facts come from

Requirement text: bedrock-cmmc-api@89b8e8e:migrations/004_reference_requirements.sql#Requirement.basicRequirement@rev2
Discussion: bedrock-cmmc-api@89b8e8e:migrations/004_reference_requirements.sql#Requirement.discussion@rev2
Practice name: bedrock-cmmc-api@89b8e8e:migrations/004_reference_requirements.sql#Requirement.title@rev2 (CMMC Assessment Guide practice name)
Objectives: bedrock-cmmc-api@89b8e8e:migrations/005_reference_objectives.sql#AssessmentObjective.description@rev2
Examine, interview, test: bedrock-cmmc-api@89b8e8e:migrations/005_reference_objectives.sql#AssessmentObjective.description@rev2 ({examineGuidance, interviewGuidance, testGuidance})
Level: bedrock-cmmc-api@89b8e8e:migrations/021_fix_level1_requirements.sql#Requirement.cmmcLevel@rev2
Weight: bedrock-cmmc-api@89b8e8e:internal/cmmc/requirement_values.go#requirementValues (DoD AM v1.2.1 / eMASS L2 template v3.8)
Rev. 3 mapping: bedrock-cmmc-api@89b8e8e:docs/reference/nist-800-171-rev3/normalized/r2_r3_transition_map.json#r2_to_r3
Plain-language title and summary: editorial/CMMC Navigator.dc.html#RAW (Foxx Cyber editorial)