Question 10 of 968
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CAS-004 Practice Question: An architect is designing a multi-factor…
An architect is designing a multi-factor authentication (MFA) solution for remote access. Which of the following is the STRONGEST form of second factor?
⚠ Common exam trap
CompTIA often tests the misconception that SMS OTP or email OTP is 'strong enough' for remote access, but the trap here is that candidates overlook the fundamental security advantage of hardware-bound private keys over shared-secret OTPs, especially against phishing and relay attacks.
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
✓
FIDO2 WebAuthn hardware token
FIDO2 WebAuthn hardware tokens provide the strongest second factor because they use public-key cryptography to generate a unique key pair per service, with the private key stored securely on the token. This eliminates phishing, man-in-the-middle, and replay attacks, as the token signs a challenge from the relying party without ever sharing a shared secret over the network.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Email OTP
Why it's wrong here
Email accounts can be compromised and are less secure.
- ✓
FIDO2 WebAuthn hardware token
Why this is correct
FIDO2 uses public-key cryptography and is resistant to phishing.
- ✗
SMS one-time code
Why it's wrong here
SMS can be intercepted via SIM swapping or SS7 attacks.
- ✗
Knowledge-based questions
Why it's wrong here
Knowledge-based questions are easily guessed or obtained through social engineering.
Quick reference
Asymmetric Encryption Algorithm Comparison
| Algorithm | Key Exchange | Signatures | Equivalent Security Key | Notes |
|---|---|---|---|---|
| RSA-3072 | Yes | Yes | 128-bit | Widely deployed; slow for bulk data |
| ECDSA P-256 | No | Yes | 128-bit | Fast signatures; standard TLS certs |
| ECDH / ECDHE | Yes | No | 128-bit | Perfect forward secrecy in TLS 1.3 |
| DH / DHE | Yes | No | 128-bit (3072-bit key) | Replaced by ECDHE in modern TLS |
| Ed25519 | No | Yes | ~128-bit | SSH keys, modern PKI |
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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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