- A
ECB
Why wrong: ECB is insecure and does not provide authentication.
- B
CBC
Why wrong: CBC provides encryption but not authentication.
- C
CTR
Why wrong: CTR provides encryption but not authentication.
- D
GCM
GCM provides authenticated encryption.
Question 657 of 1,000
SSCP Cryptography Practice Question
This SSCP practice question tests your understanding of cryptography. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
A security analyst is evaluating encryption modes for a new system that requires authenticated encryption to ensure both confidentiality and integrity of data in transit. Which AES mode should the analyst recommend?
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 authenticated encryption, combining the confidentiality of CTR mode with integrity verification via a Galois field authentication tag. This makes it ideal for securing data in transit, as it ensures both privacy and tamper detection in a single, efficient operation.
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 is insecure and does not provide authentication.
- ✗
CBC
Why it's wrong here
CBC provides encryption but not authentication.
- ✗
CTR
Why it's wrong here
CTR provides encryption but not authentication.
- ✓
GCM
Why this is correct
GCM provides authenticated encryption.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse confidentiality-only modes (like CBC or CTR) with authenticated encryption, overlooking that GCM is the only option listed that natively provides both encryption and integrity in a single mode.
Detailed technical explanation
How to think about this question
GCM operates by combining CTR mode for encryption with a universal hash function (GHASH) over the ciphertext and associated data to produce a 128-bit authentication tag. This tag is computed using multiplication in GF(2^128), enabling efficient hardware acceleration and parallel processing. In real-world scenarios, GCM is widely used in TLS 1.2/1.3 (e.g., TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) and IPsec, where the nonce (IV) must never be reused with the same key to avoid catastrophic security failures.
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 authenticated encryption, combining the confidentiality of CTR mode with integrity verification via a Galois field authentication tag. This makes it ideal for securing data in transit, as it ensures both privacy and tamper detection in a single, efficient operation.
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
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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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