DVA-C02 Security Practice Question
A developer is using AWS KMS to encrypt data in an S3 bucket. The developer wants to ensure that the S3 bucket uses server-side encryption with AWS KMS managed keys (SSE-KMS) by default. Which configuration should be applied?
⚠ Common exam trap
A common mix-up: candidates confuse enforcing encryption via a bucket policy (Option A) with setting a default encryption configuration, but the policy only denies non-compliant requests without establishing a default, whereas the default encryption setting automatically applies encryption to all objects regardless of request headers.
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
✓
Set the bucket's default encryption to SSE-KMS with a KMS key.
Setting the bucket's default encryption to SSE-KMS with a KMS key ensures that all objects uploaded to the S3 bucket are automatically encrypted using server-side encryption with AWS KMS managed keys (SSE-KMS). This configuration enforces encryption at rest without requiring the client to specify encryption headers in the request, meeting the requirement for default SSE-KMS encryption.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Add a bucket policy that denies PutObject without the 'x-amz-server-side-encryption' header set to 'aws:kms'.
Why it's wrong here
This bucket policy enforces that any PutObject request *must* include the 'x-amz-server-side-encryption' header set to 'aws:kms'. While it prevents unencrypted uploads by denying them, it does not *automatically* encrypt objects with KMS if the header is omitted. Instead, such uploads would be denied, requiring the client to explicitly specify SSE-KMS, which doesn't fulfill the requirement for *default* encryption.
- ✗
Configure the bucket to use SSE-C with a customer-provided key.
Why it's wrong here
SSE-C (Server-Side Encryption with Customer-Provided Keys) requires the customer to provide their own encryption key as part of every upload and download request. This approach places the entire responsibility for key generation, storage, and management on the customer, completely bypassing AWS KMS. Therefore, it does not align with the question's premise of the developer using AWS KMS for encryption.
- ✗
Set the bucket's default encryption to SSE-S3.
Why it's wrong here
Setting the bucket's default encryption to SSE-S3 means that Amazon S3 manages the encryption keys entirely. These keys are unique for each object and are encrypted with a master key rotated regularly by AWS. However, SSE-S3 does not integrate with AWS Key Management Service (KMS), which is explicitly stated as the service the developer is using for encryption, making it an unsuitable choice.
- ✓
Set the bucket's default encryption to SSE-KMS with a KMS key.
Why this is correct
Configuring the S3 bucket's default encryption to SSE-KMS with a specified AWS KMS key ensures that all new objects uploaded to the bucket are automatically encrypted using that KMS key. This method directly leverages AWS KMS for key management, providing centralized control, auditability through CloudTrail, and integration with IAM policies, precisely meeting the requirement to use AWS KMS for data encryption.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
Go deeper
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DVA-C02 practice question is part of Courseiva's free Amazon Web Services 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 DVA-C02 exam.