SSCP Cryptography Practice Question
An organization wants to implement a key exchange mechanism that provides forward secrecy. Which of the following should be used?
⚠ Common exam trap
SSCP often tests the misconception that any Diffie-Hellman provides forward secrecy — candidates must distinguish ephemeral DH (fresh keys per session) from static DH (reused keys), and recognize that RSA key exchange lacks forward secrecy entirely.
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
✓
Ephemeral Diffie-Hellman
Ephemeral Diffie-Hellman (DHE or ECDHE) generates a fresh key pair for each session, so even if the long-term private key is compromised later, past session keys cannot be derived. This property is forward secrecy. It is the standard mechanism used in TLS 1.3 and modern cipher suites (e.g., ECDHE-RSA-AES256-GCM-SHA384).
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Pre-shared key
Why it's wrong here
A pre-shared key is a fixed secret reused across sessions, so its compromise exposes all past and future traffic, providing no forward secrecy. It is tempting because PSKs are simple to deploy, and would be correct in constrained environments where certificate infrastructure is unavailable.
- ✓
Ephemeral Diffie-Hellman
Why this is correct
Ephemeral Diffie-Hellman generates a fresh, temporary key pair for each session, so compromising a long-term private key cannot decrypt previously captured traffic. This property is forward secrecy, exactly the mechanism the organisation requires, whereas static Diffie-Hellman or RSA key transport reuse persistent keys and lack it.
- ✗
RSA key exchange
Why it's wrong here
RSA key exchange encrypts the session key with the server's long-term certificate, so anyone later obtaining that private key can decrypt all recorded sessions; it provides no forward secrecy. It is tempting because RSA remains valid for authentication and signatures, and would suit scenarios where forward secrecy is not required.
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Static Diffie-Hellman
Why it's wrong here
Static Diffie-Hellman derives keys from long-term private values, so compromise of those values decrypts all recorded sessions, defeating forward secrecy. It is tempting because Diffie-Hellman is a genuine key exchange, and would be correct where forward secrecy is not required.
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 |
About these practice questions
Courseiva writes every SSCP question from scratch — 971 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official ISC2 exam blueprint
This SSCP 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 SSCP exam.