- A
Use envelope encryption where a cloud KMS wraps a data key, and the data key is used to encrypt the data.
Why wrong: The master key would be in the cloud KMS, not under the company's exclusive control.
- B
Use server-side encryption with customer-provided keys (SSE-C).
Why wrong: The key is provided by the customer but still used by the cloud server; the cloud provider may have access to the key during encryption/decryption.
- C
Use server-side encryption with cloud provider-managed keys (SSE-S3).
Why wrong: The key is managed by the cloud provider, not the company's HSM.
- D
Use client-side encryption where the application encrypts data before sending it to the cloud.
The company controls the encryption key entirely on-premises; the cloud only stores ciphertext.
CAS-004 Security Architecture Practice Question
This CAS-004 practice question tests your understanding of security architecture. 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 architect is evaluating cloud security architectures. The company requires that all data at rest in a public cloud object storage bucket be encrypted with a key that is managed by the company's own hardware security module (HSM) on-premises. Which encryption approach should the architect 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
Use client-side encryption where the application encrypts data before sending it to the cloud.
Option D is correct because client-side encryption ensures the data is encrypted by the application before it is sent to the cloud, using a key managed by the company's own on-premises HSM. This approach guarantees that the cloud provider never has access to the encryption key or the plaintext data, meeting the requirement that all data at rest in the public cloud object storage bucket be encrypted with a key managed by the company's own HSM.
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 envelope encryption where a cloud KMS wraps a data key, and the data key is used to encrypt the data.
Why it's wrong here
The master key would be in the cloud KMS, not under the company's exclusive control.
- ✗
Use server-side encryption with customer-provided keys (SSE-C).
Why it's wrong here
The key is provided by the customer but still used by the cloud server; the cloud provider may have access to the key during encryption/decryption.
- ✗
Use server-side encryption with cloud provider-managed keys (SSE-S3).
Why it's wrong here
The key is managed by the cloud provider, not the company's HSM.
- ✓
Use client-side encryption where the application encrypts data before sending it to the cloud.
Why this is correct
The company controls the encryption key entirely on-premises; the cloud only stores ciphertext.
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 'customer-provided keys' (SSE-C) with true client-side key management, but SSE-C still exposes the key to the cloud provider during the encryption/decryption process, failing the requirement for the key to be managed solely by the company's own on-premises HSM.
Detailed technical explanation
How to think about this question
Client-side encryption typically uses a library like AWS SDK's AmazonS3EncryptionClient or Azure Storage Client Library, where the application generates a data key, encrypts it with a master key stored in the on-premises HSM (e.g., using PKCS#11 interface), and then uploads the encrypted data and the encrypted data key to the cloud. The cloud provider only stores the ciphertext and the encrypted data key, never having access to the plaintext key or data, which aligns with regulatory requirements like PCI-DSS or HIPAA where key material must remain under the organization's physical control.
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.
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FAQ
Questions learners often ask
What does this CAS-004 question test?
Security Architecture — This question tests Security Architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use client-side encryption where the application encrypts data before sending it to the cloud. — Option D is correct because client-side encryption ensures the data is encrypted by the application before it is sent to the cloud, using a key managed by the company's own on-premises HSM. This approach guarantees that the cloud provider never has access to the encryption key or the plaintext data, meeting the requirement that all data at rest in the public cloud object storage bucket be encrypted with a key managed by the company's own HSM.
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.
About these practice questions
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Last reviewed: Jun 11, 2026
This CAS-004 practice question is part of Courseiva's free CompTIA 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 CAS-004 exam.
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