CAS-004 Security Architecture Practice Question
A security architect is designing a cryptographic system for a government agency that must protect classified data for the next 30 years. The agency is concerned about the threat from quantum computers. Which NIST post-quantum cryptography algorithm is recommended for key encapsulation?
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
✓
CRYSTALS-Kyber
CRYSTALS-Kyber is a key encapsulation mechanism (KEM) selected by NIST for general encryption. CRYSTALS-Dilithium is a digital signature algorithm. RSA and ECDH are vulnerable to quantum attacks.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
ECDH with NIST P-384
Why it's wrong here
ECDH is based on elliptic curve cryptography, which is vulnerable to quantum attacks.
- ✓
CRYSTALS-Kyber
Why this is correct
CRYSTALS-Kyber is a NIST-selected PQC algorithm for key encapsulation, designed to resist quantum attacks.
- ✗
CRYSTALS-Dilithium
Why it's wrong here
CRYSTALS-Dilithium is a digital signature algorithm, not a key encapsulation mechanism.
- ✗
RSA-4096
Why it's wrong here
RSA is vulnerable to quantum attacks (Shor's algorithm) and not considered quantum-resistant.
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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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.