PCSE Ensuring Data Protection Practice Question
A company uses Cloud KMS with automatic rotation enabled for a symmetric key. The rotation period is set to 90 days. After 90 days, a new key version is created. The compliance team asks: what happens to data encrypted with the old key version?
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 available for decryption of existing data.
When a key is rotated, a new version is created. Data encrypted with the old version can still be decrypted because the old version remains available for decryption. The key material is not destroyed unless manually deleted. Automatic rotation does not re-encrypt existing data.
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 remains available for decryption of existing data.
Why this is correct
Old key versions are retained and can decrypt data encrypted with them.
- ✗
The old key version is immediately disabled, and all data must be re-encrypted.
Why it's wrong here
Old versions remain enabled for decryption.
- ✗
Data encrypted with the old key is automatically re-encrypted with the new key.
Why it's wrong here
Automatic re-encryption is not performed.
- ✗
The old key version is deleted after the rotation period.
Why it's wrong here
Deletion is not automatic; it requires manual action.
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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JA
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.