- A
Support for RC4 encryption
Why wrong: RC4 is removed in TLS 1.3 due to weaknesses.
- B
Support for DES and 3DES
Why wrong: DES and 3DES are removed in TLS 1.3.
- C
Mandatory forward secrecy
TLS 1.3 enforces forward secrecy by using ephemeral Diffie-Hellman.
- D
Use of static RSA key exchange
Why wrong: Static RSA is removed; TLS 1.3 requires ephemeral key exchange.
Question 431 of 1,000
CISSP Communication and Network Security Practice Question
This CISSP practice question tests your understanding of communication and network security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which of the following is a key feature of TLS 1.3 that enhances security compared to earlier versions?
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
✓
Mandatory forward secrecy
TLS 1.3 mandates forward secrecy by requiring ephemeral Diffie-Hellman (DHE or ECDHE) key exchange for all sessions, eliminating static RSA and static DH key exchanges. This ensures that even if the server's long-term private key is compromised, past session keys cannot be derived, protecting historical traffic. Earlier TLS versions allowed static key exchanges, making them vulnerable to retrospective decryption.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Support for RC4 encryption
Why it's wrong here
RC4 is removed in TLS 1.3 due to weaknesses.
- ✗
Support for DES and 3DES
Why it's wrong here
DES and 3DES are removed in TLS 1.3.
- ✓
Mandatory forward secrecy
Why this is correct
TLS 1.3 enforces forward secrecy by using ephemeral Diffie-Hellman.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use of static RSA key exchange
Why it's wrong here
Static RSA is removed; TLS 1.3 requires ephemeral key exchange.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'forward secrecy' with 'encryption strength' or 'cipher support,' and may incorrectly think that simply using a strong cipher like AES provides forward secrecy, when in fact it is the key exchange mechanism (ephemeral vs. static) that determines whether past sessions remain secure after key compromise.
Detailed technical explanation
How to think about this question
Forward secrecy in TLS 1.3 is achieved by using ephemeral Diffie-Hellman key exchange (ECDHE or DHE) where each session generates a unique, temporary key pair that is discarded after the session ends. The server's long-term certificate is only used for authentication (signing the ephemeral public key), not for key agreement. In practice, this means an attacker who records encrypted traffic and later steals the server's private key cannot decrypt past sessions—a critical protection against mass surveillance and data breaches.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
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 |
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this CISSP question test?
Communication and Network Security — This question tests Communication and Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Mandatory forward secrecy — TLS 1.3 mandates forward secrecy by requiring ephemeral Diffie-Hellman (DHE or ECDHE) key exchange for all sessions, eliminating static RSA and static DH key exchanges. This ensures that even if the server's long-term private key is compromised, past session keys cannot be derived, protecting historical traffic. Earlier TLS versions allowed static key exchanges, making them vulnerable to retrospective decryption.
What should I do if I get this CISSP question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jul 4, 2026
This CISSP practice question is part of Courseiva's free ISC2 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 CISSP exam.
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