Google PCA Designing for Security and Compliance Practice Question
A company wants to encrypt data at rest in Cloud Storage using a key that they generate and manage themselves, not stored in Google Cloud. Which encryption type should they use?
⚠ Common exam trap
PCA often tests the distinction between CMEK (key stored in Cloud KMS) and CSEK (key supplied per request, never stored by Google) — candidates frequently pick CMEK thinking 'customer-managed' means 'not stored in Google Cloud.'
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
✓
CSEK
Customer-Supplied Encryption Keys (CSEK) allow you to provide your own AES-256 key with each Cloud Storage request; Google Cloud uses the key to encrypt/decrypt data but does not store the key. This matches the requirement of a self-generated, self-managed key not stored in Google Cloud. CMEK, by contrast, stores the key in Cloud KMS.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Default encryption
Why it's wrong here
Default encryption uses Google-managed keys that the customer neither generates nor controls, so it fails the external-key requirement outright. It is tempting because it is automatic and free, and would be correct where no customer key control is needed and Google-managed protection satisfies policy.
- ✗
Cloud HSM
Why it's wrong here
Cloud HSM is a Google Cloud key-hosting service, so keys remain inside Google Cloud rather than being generated and managed by the customer externally. It is tempting because HSM-backed keys offer strong hardware protection and FIPS 140-2 Level 3 assurance, and would be correct when the customer accepts Google-hosted hardware key storage.
- ✓
CSEK
Why this is correct
Customer-supplied encryption keys (CSEKs) let you generate and manage the key material yourself; Google Cloud never stores it, satisfying the requirement that the key not reside in Google Cloud. The key is supplied per request and used transiently, unlike CMEK, where key material lives in Cloud KMS.
- ✗
CMEK with Cloud KMS
Why it's wrong here
CMEK with Cloud KMS stores and manages the key material inside Google Cloud's KMS, contradicting the requirement that keys be generated and held externally. It is tempting because CMEK gives customer control over rotation and IAM, and would be correct when the customer wants key control but accepts Google-hosted key storage.
Quick reference
Symmetric Encryption Algorithm Comparison
| Algorithm | Key Size | Block Size | Status | Notes |
|---|---|---|---|---|
| AES-128 | 128-bit | 128-bit | Current standard | NIST approved; WPA3, TLS |
| AES-256 | 256-bit | 128-bit | Current standard | Preferred for sensitive / govt data |
| 3DES | 112-bit effective | 64-bit | Deprecated (2023) | Replaced by AES |
| DES | 56-bit | 64-bit | Broken | Cracked in < 24 h; never deploy |
| ChaCha20 | 256-bit | Stream cipher | Current | TLS 1.3, WireGuard |
Go deeper
Related to this question
Learn chapter
Cloud Storage: Objects and Buckets
Key term
KMS
KMS (Key Management Service) is a Microsoft technology that automates volume licensing activation for Windows and Office products within an organization's network.
Key term
Cloud KMS
Cloud KMS (Key Management Service) is a cloud-based service that lets you create, manage, and use encryption keys to protect your data at rest and in transit.
About these practice questions
This PCA question is part of Courseiva's 807-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Google Cloud exam blueprint
This PCA practice question is part of Courseiva's free Google Cloud 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 PCA exam.