# Replay-Resistant Authentication (03.05.04)_replay-resistant-authentication

> Replay-Resistant Authentication

- Skill: `cyberstrikeus/replay-resistant-authentication-03-05-04-replay-resistant-au` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/replay-resistant-authentication-03-05-04-replay-resistant-au`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/replay-resistant-authentication-03-05-04-replay-resistant-au/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: cyberstrikeus (https://skillmd.com/u/cyberstrikeus)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/cyberstrikeus/replay-resistant-authentication-03-05-04-replay-resistant-au

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# Replay-Resistant Authentication (03.05.04) Replay-Resistant Authentication

## High-Level Description

**Family:** Identification and Authentication
**Framework:** NIST SP 800-171 Rev 3
**Applicability:** Systems processing, storing, or transmitting CUI

Replay-Resistant Authentication

## What to Check

- [ ] Verify Replay-Resistant Authentication (03.05.04) Replay-Resistant Authentication is implemented for CUI systems
- [ ] Review SSP documentation for Replay-Resistant Authentication (03.05.04)
- [ ] Validate CMMC Level 2 assessment objective for Replay-Resistant Authentication (03.05.04)
- [ ] Confirm POA&M addresses any gaps for Replay-Resistant Authentication (03.05.04)

## How to Test

### Step 1: Review System Security Plan

Examine the SSP for Replay-Resistant Authentication (03.05.04) implementation description and responsible parties.

### Step 2: Assess Implementation

```
# Verify security controls protecting CUI
# Check access controls, encryption, monitoring as applicable

# For Linux systems:
ls -la /etc/security/ 2>/dev/null
grep -r "CUI\|controlled" /etc/security/ 2>/dev/null

# For cloud:
# Use cloud-audit-mcp tools to assess posture
```

### Step 3: CMMC Assessment Validation

Verify this requirement passes CMMC Level 2 assessment methodology per SP 800-171A Rev 3.

## Tools

| Tool            | Purpose                      | Usage                  |
| --------------- | ---------------------------- | ---------------------- |
| cloud-audit-mcp | Assess cloud CUI environment | `cloud_audit_*` tools  |
| Manual Review   | SSP and POA&M review         | Documentation analysis |

## Remediation Guide

### Requirement Statement

Implement Replay-Resistant Authentication per NIST SP 800-171 Rev 3.

### Supplemental Guidance

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.

## Risk Assessment

| Finding                                                                                    | Severity | Impact                                             |
| ------------------------------------------------------------------------------------------ | -------- | -------------------------------------------------- |
| Replay-Resistant Authentication (03.05.04) Replay-Resistant Authentication not implemented | High     | CUI Protection - Identification and Authentication |
| Replay-Resistant Authentication (03.05.04) partially implemented (POA&M)                   | Medium   | CMMC certification risk                            |

## CWE Categories

| CWE ID  | Title                   |
| ------- | ----------------------- |
| CWE-287 | Improper Authentication |

## References

- [NIST SP 800-171 Rev 3](https://csrc.nist.gov/pubs/sp/800/171/r3/final)
- [NIST SP 800-171A Rev 3 (Assessment)](https://csrc.nist.gov/pubs/sp/800/171/a/r3/final)
- [CMMC Model Overview](https://www.acq.osd.mil/cmmc/)
- [NIST OSCAL Content](https://github.com/usnistgov/oscal-content)

## Checklist

- [ ] SSP documents Replay-Resistant Authentication (03.05.04) implementation
- [ ] Evidence of operating effectiveness collected
- [ ] POA&M addresses any gaps
- [ ] CMMC assessment objective met
- [ ] Continuous monitoring active