PCSE Ensuring Data Protection Practice Question
An engineer needs to configure automatic key rotation for a symmetric encryption key in Cloud KMS. They have set the rotation period to 90 days. What happens to the old key material after rotation?
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
✓
The old key version remains enabled and can still be used for decryption.
When a key is rotated, a new key version is created and becomes the primary. The old version is retained and remains available for decrypting data encrypted with it. Key material is not automatically deleted; it can be disabled or scheduled for destruction separately.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The old key version is disabled and can be re-enabled if needed.
Why it's wrong here
Key versions are not automatically disabled; they remain enabled unless manually disabled.
- ✗
The old key material is immediately deleted.
Why it's wrong here
Key material is not immediately deleted; it is retained for decryption purposes.
- ✓
The old key version remains enabled and can still be used for decryption.
Why this is correct
Old key versions remain enabled and can be used to decrypt data encrypted with them.
- ✗
The old key material is moved to a pending destruction state for 24 hours.
Why it's wrong here
Pending destruction only occurs when a key version is manually scheduled for destruction, not during rotation.
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 |
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PCSE 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 PCSE exam.