- A
ECB
Why wrong: ECB encrypts each block independently and is susceptible to pattern attacks; it should be avoided.
- B
GCM
GCM combines CTR mode with authentication tags, providing both confidentiality and integrity.
- C
CBC
Why wrong: CBC provides confidentiality but not integrity; it is not authenticated encryption.
- D
CTR
Why wrong: CTR is a stream cipher mode that provides confidentiality but no integrity.
Question 46 of 1,000
SSCP Cryptography Practice Question
This SSCP practice question tests your understanding of cryptography. 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.
An organization is migrating from 3DES to AES-256 for encrypting data at rest. Which mode of AES is recommended for authenticated encryption?
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
✓
GCM
GCM (Galois/Counter Mode) is the correct choice because it provides both confidentiality and authenticity in a single, efficient mode. For data at rest, authenticated encryption ensures that encrypted data cannot be tampered with undetected, which is critical for integrity. AES-256-GCM is widely recommended and standardized (NIST SP 800-38D) for this purpose.
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.
- ✗
ECB
Why it's wrong here
ECB encrypts each block independently and is susceptible to pattern attacks; it should be avoided.
- ✓
GCM
Why this is correct
GCM combines CTR mode with authentication tags, providing both confidentiality and integrity.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
CBC
Why it's wrong here
CBC provides confidentiality but not integrity; it is not authenticated encryption.
- ✗
CTR
Why it's wrong here
CTR is a stream cipher mode that provides confidentiality but no integrity.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that any mode providing confidentiality (like CBC or CTR) is sufficient for secure encryption, but the trap here is that authenticated encryption specifically requires a mode that also guarantees integrity, which only GCM (or CCM) provides among the listed options.
Detailed technical explanation
How to think about this question
GCM combines CTR mode for encryption with a universal hash function (GHASH) for authentication, producing an authentication tag that verifies both the ciphertext and associated data. Under the hood, GCM uses a 96-bit nonce (recommended) and a 128-bit block cipher, with the tag length typically 128 bits for maximum security. In real-world scenarios, such as encrypting database backups or disk volumes, using GCM prevents undetected tampering, which is vital for compliance with standards like FIPS 140-2.
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
Symmetric Encryption Algorithm Comparison
| Algorithm | Key Size | Block Size | Status | Notes |
|---|---|---|---|---|
| AES-128 | 128-bit | 128-bit | Current standard | NIST approved; WPA3, TLS |
| AES-256 | 256-bit | 128-bit | Current standard | Preferred for sensitive / govt data |
| 3DES | 112-bit effective | 64-bit | Deprecated (2023) | Replaced by AES |
| DES | 56-bit | 64-bit | Broken | Cracked in < 24 h; never deploy |
| ChaCha20 | 256-bit | Stream cipher | Current | TLS 1.3, WireGuard |
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 SSCP question test?
Cryptography — This question tests Cryptography — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: GCM — GCM (Galois/Counter Mode) is the correct choice because it provides both confidentiality and authenticity in a single, efficient mode. For data at rest, authenticated encryption ensures that encrypted data cannot be tampered with undetected, which is critical for integrity. AES-256-GCM is widely recommended and standardized (NIST SP 800-38D) for this purpose.
What should I do if I get this SSCP 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 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.
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