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CAS-004 Practice Question: A security architect is evaluating cloud security…
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?
⚠ Common exam trap
Watch out — 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.
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.
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.
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.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CAS-005 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-005 exam.