CAS-004 Security Engineering Practice Question
A security architect is designing a new authentication system for a high-security environment. The system must support passwordless authentication while providing strong protection against phishing attacks. Which of the following protocols best meets these requirements?
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 uses public key cryptography and is designed to resist phishing; it supports passwordless authentication. TOTP/HOTP are time-based and can be phished. X.509 certificates are not inherently passwordless. Kerberos requires passwords or tickets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Kerberos with PKINIT
Why it's wrong here
Kerberos with PKINIT uses certificates but still requires a password or PIN for the private key.
- ✓
FIDO2/WebAuthn
Why this is correct
FIDO2/WebAuthn uses device-bound keys and is phishing-resistant, enabling passwordless authentication.
- ✗
TOTP/HOTP
Why it's wrong here
TOTP/HOTP require a shared secret and are susceptible to phishing if the token is intercepted.
- ✗
X.509 certificates with smart cards
Why it's wrong here
X.509 certificates provide strong authentication but are not passwordless; they require a PIN or biometric.
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
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