Question 120 of 968
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CAS-004 Practice Question: Needs to implement a solution that provides both…
A security engineer needs to implement a solution that provides both confidentiality and integrity for data at rest. Which cryptographic method BEST meets these requirements?
⚠ Common exam trap
Candidates often confuse integrity-only tools like SHA-256 or key exchange protocols like Diffie-Hellman with solutions that provide both confidentiality and integrity, overlooking that GCM is an authenticated encryption mode specifically designed for this dual purpose.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
AES-256-GCM
AES-256-GCM is correct because it provides both confidentiality (via AES encryption) and integrity (via Galois/Counter Mode authentication tag). GCM is an authenticated encryption mode that ensures data at rest remains both secret and tamper-proof, meeting the dual requirement directly.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
AES-256-GCM
Why this is correct
AES-256-GCM provides both encryption and authentication, satisfying confidentiality and integrity requirements.
- ✗
SHA-256
Why it's wrong here
SHA-256 is a cryptographic hash function that provides integrity but not confidentiality.
- ✗
Diffie-Hellman
Why it's wrong here
Diffie-Hellman is a key exchange protocol, not used for data at rest.
- ✗
RSA-2048
Why it's wrong here
RSA is asymmetric encryption; it does not provide data integrity natively.
Quick reference
Symmetric Encryption Algorithm Comparison
| Algorithm | Key Size | Block Size | Status | Notes |
|---|---|---|---|---|
| AES-128 | 128-bit | 128-bit | Current standard | NIST approved; WPA3, TLS |
| AES-256 | 256-bit | 128-bit | Current standard | Preferred for sensitive / govt data |
| 3DES | 112-bit effective | 64-bit | Deprecated (2023) | Replaced by AES |
| DES | 56-bit | 64-bit | Broken | Cracked in < 24 h; never deploy |
| ChaCha20 | 256-bit | Stream cipher | Current | TLS 1.3, WireGuard |
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Last reviewed: Jul 4, 2026
This CAS-005 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CAS-005 exam.
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