CAS-004 Security Engineering Practice Question
A security architect is designing a new authentication system for a cloud-based application that requires strong multi-factor authentication. The solution must be resistant to phishing attacks and not rely on shared secrets. Which of the following is the BEST choice?
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
FIDO2/WebAuthn is a passwordless authentication protocol that uses public key cryptography and is resistant to phishing because the private key never leaves the user's device.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
HOTP with a hardware token
Why it's wrong here
HOTP is event-based and can be vulnerable to phishing if the OTP is intercepted.
- ✓
FIDO2/WebAuthn
Why this is correct
FIDO2/WebAuthn provides phishing-resistant, passwordless authentication using public key cryptography.
- ✗
TOTP via a mobile authenticator app
Why it's wrong here
TOTP is vulnerable to phishing and man-in-the-middle attacks.
- ✗
SMS one-time passcodes
Why it's wrong here
SMS OTP is susceptible to SIM swapping and phishing.
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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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.