This DVA-C02 practice question tests your understanding of security. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company uses AWS KMS to encrypt data in Amazon S3. They have a Customer Master Key (CMK) with key rotation enabled. The S3 bucket has default encryption using SSE-KMS with this CMK. An application writes objects to the bucket. Which statement about the encryption is correct?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The CMK is used to generate a data key that encrypts the object, and the encrypted data key is stored with the object.
Option A is correct because AWS KMS uses envelope encryption: when an object is written to S3 with SSE-KMS, KMS generates a unique data key from the CMK, encrypts the object with that data key, and then stores the encrypted data key alongside the object in S3. The CMK itself never directly encrypts the object data; it only encrypts the data key. This ensures that the CMK can be rotated without affecting the encrypted objects, as the encrypted data key remains decryptable by the new key material if the key ID is the same.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 CMK is used to generate a data key that encrypts the object, and the encrypted data key is stored with the object.
Why this is correct
This is the correct description of envelope encryption with KMS.
Related concept
Read the scenario before looking for a memorised answer.
✗
The CMK directly encrypts the object data.
Why it's wrong here
KMS uses envelope encryption: the CMK encrypts a data key, and that data key encrypts the object.
✗
When the CMK is rotated, all existing objects in the bucket are automatically re-encrypted with the new key.
Why it's wrong here
Key rotation does not re-encrypt existing objects; they remain encrypted with the old data key.
✗
Each object is encrypted with a unique data key that is stored alongside the object.
Why it's wrong here
The encrypted data key is stored in the object metadata, but the data key is not the CMK.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the role of the CMK and the data key, mistakenly thinking the CMK directly encrypts the object (Option B), or they assume key rotation triggers re-encryption of existing data (Option C), when in fact envelope encryption decouples the key rotation from the stored ciphertext.
Detailed technical explanation
How to think about this question
Under the hood, when SSE-KMS is used, S3 calls the KMS GenerateDataKey API to get a plaintext data key and an encrypted copy of that data key (ciphertext blob). The plaintext data key is used to encrypt the object with AES-256 in the S3 server, then discarded; only the encrypted data key is stored as part of the object metadata. When the object is retrieved, S3 calls KMS Decrypt with the encrypted data key to get the plaintext data key back, then decrypts the object. This design means that even if the CMK is rotated (creating new backing key material), the old backing key is retained for decryption of existing encrypted data keys, so objects are never re-encrypted automatically.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Security — This question tests Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The CMK is used to generate a data key that encrypts the object, and the encrypted data key is stored with the object. — Option A is correct because AWS KMS uses envelope encryption: when an object is written to S3 with SSE-KMS, KMS generates a unique data key from the CMK, encrypts the object with that data key, and then stores the encrypted data key alongside the object in S3. The CMK itself never directly encrypts the object data; it only encrypts the data key. This ensures that the CMK can be rotated without affecting the encrypted objects, as the encrypted data key remains decryptable by the new key material if the key ID is the same.
What should I do if I get this DVA-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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