IA 5(2) Public Key Based Authentication

---
name: "IA-5(2)_public-key-based-authentication"
description: "For public key-based authentication: Enforce authorized access to the corresponding private key; and Map the authenticated identity to the account of "
category: "authentication"
version: "5.2.0"
author: "cyberstrike-official"
tags:
  - nist
  - sp800-53
  - rev5
  - ia-5-2
  - ia
  - enhancement
tech_stack:
  - aws
  - azure
  - active-directory
  - linux
  - windows
cwe_ids:
  - CWE-287
chains_with:
  - IA-3
  - SC-17
prerequisites:
  - IA-5
severity_boost:
  IA-3: "Chain with IA-3 for comprehensive security coverage"
  SC-17: "Chain with SC-17 for comprehensive security coverage"
---

# IA-5(2) Public Key-based Authentication

> **Enhancement of:** IA-5

## High-Level Description

**Family:** Identification and Authentication (IA)
**Framework:** NIST SP 800-53 Rev 5

Public key cryptography is a valid authentication mechanism for individuals, machines, and devices. For PKI solutions, status information for certification paths includes certificate revocation lists or certificate status protocol responses. For PIV cards, certificate validation involves the construction and verification of a certification path to the Common Policy Root trust anchor, which includes certificate policy processing. Implementing a local cache of revocation data to support path discovery and validation also supports system availability in situations where organizations are unable to access revocation information via the network.

## What to Check

- [ ] Verify IA-5(2) Public Key-based Authentication is documented in SSP
- [ ] Validate all 4 control requirements are implemented
- [ ] Confirm control is operating effectively
- [ ] Review evidence of continuous monitoring for IA-5(2)
- [ ] Verify enhancement builds upon base control IA-5

## How to Test

### Step 1: Review Documentation

Examine the System Security Plan (SSP) and related artifacts for IA-5(2) implementation details. Verify the organization has documented how this control is satisfied.

### Step 2: Validate Implementation

```
# For cloud environments, use cloud-audit-mcp tools
# For on-premises, review system configurations directly

# Example: Check if account management policies exist
grep -r "account.management\|access.control" /etc/security/ 2>/dev/null
```

### Step 3: Test Operating Effectiveness

Verify the control is actively functioning, not just documented. Check logs, configurations, and operational evidence.

## Tools

| Tool            | Purpose                        | Usage                      |
| --------------- | ------------------------------ | -------------------------- |
| cloud-audit-mcp | Check authentication settings  | `cloud_audit_iam_policies` |
| hackbrowser | Test authentication mechanisms | `hackbrowser`        |

## Remediation Guide

### Control Statement

For public key-based authentication:
Enforce authorized access to the corresponding private key; and
Map the authenticated identity to the account of the individual or group; and
When public key infrastructure (PKI) is used:
Validate certificates by constructing and verifying a certification path to an accepted trust anchor, including checking certificate status information; and
Implement a local cache of revocation data to support path discovery and validation.

### Implementation Guidance

Public key cryptography is a valid authentication mechanism for individuals, machines, and devices. For PKI solutions, status information for certification paths includes certificate revocation lists or certificate status protocol responses. For PIV cards, certificate validation involves the construction and verification of a certification path to the Common Policy Root trust anchor, which includes certificate policy processing. Implementing a local cache of revocation data to support path discovery and validation also supports system availability in situations where organizations are unable to access revocation information via the network.

## Risk Assessment

| Finding                                                 | Severity | Impact                                       |
| ------------------------------------------------------- | -------- | -------------------------------------------- |
| IA-5(2) Public Key-based Authentication not implemented | High     | Identification and Authentication            |
| IA-5(2) partially implemented                           | Medium   | Incomplete Identification and Authentication |

## CWE Categories

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

## References

- [NIST SP 800-53 Rev 5 - IA-5(2)](https://csrc.nist.gov/projects/cprt/catalog#/cprt/framework/version/SP_800_53_5_1_1/home?element=ia-5.2)
- [NIST SP 800-53A Rev 5 (Assessment Procedures)](https://csrc.nist.gov/pubs/sp/800/53/a/r5/final)
- [NIST SP 800-53 Rev 5 Full Catalog](https://csrc.nist.gov/pubs/sp/800/53/r5/upd1/final)

## Checklist

- [ ] Control documented in SSP
- [ ] Implementation evidence collected
- [ ] Operating effectiveness validated
- [ ] Continuous monitoring in place
- [ ] Related controls (IA-3, SC-17) reviewed