CAS-004 Security Engineering Practice Question
A security analyst is reviewing TLS 1.3 configuration for a web server. The analyst wants to ensure that the configuration provides forward secrecy and prevents the reuse of session keys. Which of the following is a characteristic of TLS 1.3 that supports these goals?
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
✓
Use of ephemeral Diffie-Hellman key exchange
TLS 1.3 mandates ephemeral Diffie-Hellman key exchange (ECDHE or DHE), which provides forward secrecy by generating unique session keys for each session.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
0-RTT session resumption
Why it's wrong here
0-RTT allows resumption but may reuse keys if not properly managed.
- ✗
Support for static RSA key exchange
Why it's wrong here
Static RSA does not provide forward secrecy.
- ✓
Use of ephemeral Diffie-Hellman key exchange
Why this is correct
Ephemeral Diffie-Hellman ensures that session keys are not derived from long-term keys, providing forward secrecy.
- ✗
Removal of CBC mode cipher suites
Why it's wrong here
While CBC is removed, this alone does not guarantee forward secrecy.
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.