hardMultiple Choice
CISA Practice Question: Designing a public cloud-based application that…
A company is designing a public cloud-based application that processes highly sensitive personal data. Which of the following data protection strategies provides the STRONGEST assurance that data remains confidential even if the cloud provider's infrastructure is compromised?
⚠ Common exam trap
It's easy for candidates to confuse 'encryption at rest' (server-side) with 'end-to-end confidentiality' and assume that any encryption managed by the cloud provider is sufficient, failing to recognize that provider-managed keys are still accessible to the provider and thus vulnerable in a provider compromise scenario.
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 client-side encryption with customer managed keys
Client-side encryption with customer managed keys ensures that data is encrypted before it leaves the client environment, and the cloud provider never has access to the plaintext data or the encryption keys. Even if the cloud provider's infrastructure is fully compromised, the attacker cannot decrypt the data because the keys are never stored or processed by the provider. This provides the strongest assurance of confidentiality because the data remains encrypted end-to-end, independent of the provider's security controls.
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 server-side encryption with cloud provider managed keys
Why it's wrong here
Provider-managed keys leave the cloud provider holding both ciphertext and decryption capability, so infrastructure compromise yields plaintext. It is tempting because server-side encryption is effortless and satisfies baseline compliance, but it is the right choice only when the provider is fully trusted and regulatory custody requirements are absent.
- ✓
Implement client-side encryption with customer managed keys
Why this is correct
Client-side encryption ensures plaintext never reaches provider infrastructure, so a compromised hypervisor or storage layer yields only ciphertext. Customer-managed keys in an external key store keep decryption authority with the organisation, satisfying the stem's requirement for confidentiality despite full provider compromise. Provider-side controls cannot match this, since they operate on data the provider can already access.
- ✗
Enable encryption in transit using TLS 1.3
Why it's wrong here
TLS 1.3 protects data only while traversing the network; once decrypted at the provider's endpoint, plaintext is exposed to compromised infrastructure. It is tempting because transport encryption is mandatory for regulatory compliance and defends against interception, but it cannot address at-rest exposure within the provider's environment.
- ✗
Apply data masking at the application layer
Why it's wrong here
Masking at the application layer still leaves the underlying stored data readable, so compromise of the provider's infrastructure exposes the real values. Masking is tempting because it limits what application users see, but it protects presentation, not storage; only encryption with keys held outside the provider does that.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CISA practice question is part of Courseiva's free ISACA 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 CISA exam.