The answer is envelope encryption, which combines a data encryption key (DEK) wrapped by a key encryption key (KEK) to protect cloud data at rest. This method is correct because it allows client-side encryption with key management, ensuring data is encrypted before it leaves the client device so the cloud provider never accesses plaintext or the keys—a critical control for untrusted environments. On the CISSP exam, this tests your understanding of cryptographic separation of duties and the Cloud Data at Rest Encryption Methods domain, often appearing in scenario-based questions where a company must retain sole control over encryption keys. A common trap is confusing envelope encryption with server-side options like SSE-S3, which still expose data to the provider. Memory tip: think of a “nested doll” where the DEK is the inner secret, and the KEK is the outer lock only you hold.
CISSP Security Architecture and Engineering Practice Question
This CISSP practice question tests your understanding of security architecture and engineering. 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 company needs to protect data at rest in a cloud storage system. Which THREE encryption methods are appropriate for this purpose?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Client-side encryption with key management
Client-side encryption with key management (B) ensures data is encrypted before it leaves the client device, so the cloud provider never has access to plaintext or the encryption keys. This is a fundamental control for protecting data at rest in untrusted environments, as it decouples key management from the storage provider.
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.
✗
Stream cipher without authentication (e.g., RC4)
Why it's wrong here
Stream ciphers without authentication are vulnerable to bit-flipping attacks.
✓
Client-side encryption with key management
Why this is correct
Client-side encryption ensures data is encrypted before reaching the cloud, and keys are controlled by the client.
Related concept
Read the scenario before looking for a memorised answer.
✗
MD5 hashing
Why it's wrong here
MD5 is a hash, not encryption; it does not protect confidentiality.
✓
AES-256 in GCM mode
Why this is correct
AES-256-GCM provides confidentiality and integrity.
Related concept
Read the scenario before looking for a memorised answer.
✓
Envelope encryption
Why this is correct
Envelope encryption uses a data encryption key (DEK) wrapped by a key encryption key (KEK) for efficient and secure key management.
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 may confuse hashing (MD5) with encryption, or assume that any cipher (like RC4) is acceptable for data at rest, ignoring the critical need for authentication and integrity in storage systems.
Detailed technical explanation
How to think about this question
Envelope encryption (E) combines a data encryption key (DEK) with a key encryption key (KEK), allowing the DEK to be stored alongside the ciphertext while the KEK is managed separately, often in a hardware security module (HSM) or key management service. AES-256 in GCM mode (D) provides both confidentiality and authenticated encryption via Galois/Counter Mode, which includes an integrity check (GMAC) that detects tampering. In practice, cloud providers like AWS S3 use envelope encryption with AES-256-GCM for server-side encryption, but client-side encryption gives the customer full control over keys.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CISSP question in full detail.
Security Architecture and Engineering — This question tests Security Architecture and Engineering — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Client-side encryption with key management — Client-side encryption with key management (B) ensures data is encrypted before it leaves the client device, so the cloud provider never has access to plaintext or the encryption keys. This is a fundamental control for protecting data at rest in untrusted environments, as it decouples key management from the storage provider.
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.
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Question Discussion
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