CAS-004 Security Architecture Practice Question
To protect against quantum computing attacks, a security architect is planning to transition to post-quantum cryptography. Which algorithm has been selected by NIST for general encryption (key encapsulation) in the PQC standard?
⚠ Common exam trap
The trap is confusing NIST's PQC selections — candidates must remember Kyber is the KEM for encryption, while Dilithium, Falcon, and SPHINCS+ are signature algorithms.
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
NIST selected CRYSTALS-Kyber as the primary standard for general encryption and key encapsulation (FIPS 203) in its post-quantum cryptography program. Kyber is a lattice-based KEM designed for efficient key establishment, making it the correct choice for general encryption.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Falcon
Why it's wrong here
Falcon is a NIST-selected digital signature scheme, so it provides authentication and integrity rather than the key encapsulation mechanism general encryption needs. It is tempting because it is a legitimate post-quantum standard, and it would be correct if the scenario required signing rather than encrypting data.
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CRYSTALS-Dilithium
Why it's wrong here
CRYSTALS-Dilithium is a NIST post-quantum signature algorithm, not key encapsulation, so it cannot provide the general encryption the scenario requires. It is tempting because it is a genuine NIST PQC selection, but it belongs in digital-signature and authentication use cases, whereas CRYSTALS-Kyber was chosen for key encapsulation.
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CRYSTALS-Kyber
Why this is correct
CRYSTALS-Kyber is the NIST-selected key encapsulation mechanism, standardised as ML-KEM (FIPS 203), designed for general encryption against quantum attacks. It satisfies the stem's requirement for a post-quantum key encapsulation algorithm, unlike CRYSTALS-Dilithium or Falcon, which NIST selected for digital signatures rather than encryption.
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SPHINCS+
Why it's wrong here
SPHINCS+ is a stateless hash-based signature scheme selected by NIST for digital signatures, not for key encapsulation. It is the correct choice when long-term signature security against quantum attack is required, whereas general encryption needs ML-KEM (CRYSTALS-Kyber).
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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.