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.
An organization is deploying a new cloud-based application that processes personally identifiable information (PII). The security team must ensure data at rest is encrypted. Which THREE of the following controls should be implemented to protect the data? (Select THREE.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Implement a key management system (KMS) with automatic key rotation.
Option B is correct because a key management system (KMS) with automatic key rotation ensures that encryption keys are securely stored, rotated, and managed, which is essential for protecting data at rest. Without proper key management, encryption can be rendered ineffective if keys are compromised or stale. This control directly supports the confidentiality of PII stored in the cloud.
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.
✗
Use tokenization for all PII fields in the database.
Why it's wrong here
Tokenization is a data masking technique, not encryption at rest.
✓
Implement a key management system (KMS) with automatic key rotation.
Why this is correct
Proper key management and rotation are critical to maintaining encryption security.
Related concept
Read the scenario before looking for a memorised answer.
✓
Enable transparent data encryption (TDE) on the database.
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between encryption for data at rest (e.g., TDE, AES-256, KMS) and encryption for data in transit (e.g., TLS), so candidates mistakenly select TLS as a data-at-rest control.
Detailed technical explanation
How to think about this question
Transparent data encryption (TDE) performs real-time I/O encryption and decryption of data and log files at the storage layer, using a database encryption key (DEK) stored in the database boot record, which is protected by a certificate or asymmetric key managed by the KMS. AES-256 is a symmetric block cipher that encrypts data in 128-bit blocks with a 256-bit key, providing strong cryptographic protection for stored data. In a cloud environment, KMS integration with automatic rotation (e.g., every 90 days) reduces the risk of key exposure and meets compliance requirements like PCI DSS or GDPR.
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 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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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 a key management system (KMS) with automatic key rotation. — Option B is correct because a key management system (KMS) with automatic key rotation ensures that encryption keys are securely stored, rotated, and managed, which is essential for protecting data at rest. Without proper key management, encryption can be rendered ineffective if keys are compromised or stale. This control directly supports the confidentiality of PII stored in the cloud.
What should I do if I get this CAS-004 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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