Question 38 of 510

Security Engineering →hardMultiple ChoiceObjective-mapped

Quick Answer

The correct choice is envelope encryption with a unique data encryption key per tenant, wrapped by a key encryption key stored in an HSM. This approach directly addresses the need for multi-tenant key rotation with minimal performance impact because the data encryption keys (DEKs) can be independently rotated by simply generating a new DEK and re-wrapping it with the same KEK, without re-encrypting the underlying data. On the CompTIA SecurityX CAS-004 exam, this scenario tests your understanding of cryptographic isolation and operational efficiency in cloud storage—a common trap is choosing a single master key for all tenants, which violates separation and creates a single point of failure. Remember the memory tip: “Wrap the DEK, not the data” to keep rotation fast and tenant keys isolated.

CAS-004 Security Engineering Practice Question

This CAS-004 practice question tests your understanding of security 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 security engineer is tasked with designing a cryptographic solution to protect data at rest in a multi-tenant cloud storage system. Each tenant's data must be encrypted with a unique key, and the system must support key rotation with minimal performance impact. Which of the following is the BEST approach?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.

Question 1hardmultiple choice

Full question →

A
Generate a unique key per tenant and encrypt each key with a master key, then store both in the same database column.
Why wrong: Storing encrypted keys in the same database as the data reduces security; an attacker who gains database access could try to compromise the keys.
B
Implement envelope encryption: generate a unique data encryption key (DEK) per tenant, encrypt each DEK with a key encryption key (KEK) stored in an HSM, and store the wrapped DEK alongside the data.
Envelope encryption allows per-tenant isolation, easy key rotation (by rewrapping DEKs with new KEKs), and minimal performance impact since data is not re-encrypted on rotation.
C
Use a single master key for all tenants and store the key in a hardware security module (HSM) with access controls.
Why wrong: A single master key means all tenants share the same encryption; a breach of the master key compromises all data, and rotation affects everyone.
D
Implement a periodic key rotation schedule that rotates all tenant keys every month manually.
Why wrong: Manual rotation is error-prone, not scalable, and does not address per-tenant key management; also performance impact can be high if re-encrypting all data.

Full breakdown with real-world context →

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

✓

Implement envelope encryption: generate a unique data encryption key (DEK) per tenant, encrypt each DEK with a key encryption key (KEK) stored in an HSM, and store the wrapped DEK alongside the data.

Option D is correct because envelope encryption with a unique data key per tenant allows independent rotation and minimizes performance impact by only wrapping new data keys. Option A is wrong because storing keys in the same database violates separation. Option B is wrong because a single master key for all tenants violates isolation; if compromised, all data is at risk. Option C is wrong because a monthly rotation of a single master key does not provide per-tenant isolation; also key synchronization can be complex.

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.

✗
Generate a unique key per tenant and encrypt each key with a master key, then store both in the same database column.
Why it's wrong here
Storing encrypted keys in the same database as the data reduces security; an attacker who gains database access could try to compromise the keys.
✓
Implement envelope encryption: generate a unique data encryption key (DEK) per tenant, encrypt each DEK with a key encryption key (KEK) stored in an HSM, and store the wrapped DEK alongside the data.
Why this is correct
Envelope encryption allows per-tenant isolation, easy key rotation (by rewrapping DEKs with new KEKs), and minimal performance impact since data is not re-encrypted on rotation.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use a single master key for all tenants and store the key in a hardware security module (HSM) with access controls.
Why it's wrong here
A single master key means all tenants share the same encryption; a breach of the master key compromises all data, and rotation affects everyone.
✗
Implement a periodic key rotation schedule that rotates all tenant keys every month manually.
Why it's wrong here
Manual rotation is error-prone, not scalable, and does not address per-tenant key management; also performance impact can be high if re-encrypting all data.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.

Detailed technical explanation

How to think about this question

This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.

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.
Use explanations to understand the rule behind the answer.

TExam Day Tips

Underline the problem statement mentally.
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 practitioner preparing for the CAS-004 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.

What to study next

Got this wrong? Here's your next step.

Identify which CAS-004 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.

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FAQ

Questions learners often ask

What does this CAS-004 question test?

Security Engineering — This question tests Security Engineering — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Implement envelope encryption: generate a unique data encryption key (DEK) per tenant, encrypt each DEK with a key encryption key (KEK) stored in an HSM, and store the wrapped DEK alongside the data. — Option D is correct because envelope encryption with a unique data key per tenant allows independent rotation and minimizes performance impact by only wrapping new data keys. Option A is wrong because storing keys in the same database violates separation. Option B is wrong because a single master key for all tenants violates isolation; if compromised, all data is at risk. Option C is wrong because a monthly rotation of a single master key does not provide per-tenant isolation; also key synchronization can be complex.

What should I do if I get this CAS-004 question wrong?

Are there clue words in this question I should notice?

Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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