hardMultiple Choice
CKS Practice Question: You have enabled etcd encryption at rest using an…
You have enabled etcd encryption at rest using an EncryptionConfiguration with aescbc provider. After applying the configuration, you create a new Secret. Which of the following is true regarding the encrypted Secret?
⚠ Common exam trap
Many candidates assume encryption is applied retroactively to all existing data, but Kubernetes only encrypts data at write time, so existing Secrets remain unencrypted until they are updated or re-created.
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
✓
Only the new Secret is encrypted; existing Secrets remain in plaintext.
When you apply an EncryptionConfiguration with aescbc provider, only newly created Secrets are encrypted at rest. Existing Secrets remain in plaintext because encryption is applied at write time; the API server does not retroactively re-encrypt data already stored in etcd. This is why option C is correct.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
All Secrets are encrypted because the EncryptionConfiguration applies to all resources.
Why it's wrong here
Although EncryptionConfiguration lists resource types like secrets and configmaps, it only governs data as it is written to etcd. The API server calls the configured encryption provider on the write path, but it never sweeps the etcd store to re-encrypt existing objects. Therefore, enabling the configuration does not instantly encrypt all Secrets; only new or updated resources receive encryption.
- ✗
All Secrets in the cluster, including existing ones, are immediately encrypted.
Why it's wrong here
Existing Secrets remain in plaintext until they are written again because etcd already holds their raw bytes. When the API server restarts with encryption enabled, it doesn't rewrite stored objects; it simply uses the new provider for subsequent put operations. To encrypt legacy data, administrators must perform a rolling update, for example by exporting each Secret and applying it back, forcing a rewrite.
- ✓
Only the new Secret is encrypted; existing Secrets remain in plaintext.
Why this is correct
A newly created Secret is passed through the encryption provider (here aescbc) before its bytes are stored in etcd, so only the new write is protected. Previously written Secrets are already at rest in plaintext and the API server does not proactively re-read and re-encrypt them. Without rotating, those old entries stay unencrypted until modified or deleted.
- ✗
The new Secret is stored in plaintext because aescbc is not a valid provider.
Why it's wrong here
aescbc is a legitimate, built-in provider that encrypts data with AES in CBC mode; it is commonly used for at-rest encryption. If the argument were true, the kube-apiserver would reject the EncryptionConfiguration or fail to start, so the Secret would never reach etcd. Since the configuration is loaded successfully, the new Secret is encrypted, not stored in plaintext.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CKS practice question is part of Courseiva's free CNCF 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 CKS exam.