- A
{"Effect":"Deny","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"Null":{"s3:x-amz-server-side-encryption":"true"}}}
Why wrong: This denies unencrypted requests but does not enforce the specific KMS key.
- B
{"Effect":"Allow","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"StringEquals":{"s3:x-amz-server-side-encryption-aws-kms-key-id":"arn:aws:kms:us-east-1:123456789012:key/abc123"}}}
Why wrong: This allows requests with the specific key but does not deny unencrypted requests.
- C
{"Effect":"Deny","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"StringNotEquals":{"s3:x-amz-server-side-encryption":"aws:kms"},"Null":{"s3:x-amz-server-side-encryption-aws-kms-key-id":"true"}}}
This denies if encryption is not aws:kms or if the key ID is not provided, enforcing the required encryption.
- D
{"Effect":"Deny","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"StringNotEquals":{"s3:x-amz-server-side-encryption-aws-kms-key-id":"arn:aws:kms:us-east-1:123456789012:key/abc123"}}}
Why wrong: This denies only if the key does not match, but allows unencrypted requests because the condition is not checked when the header is missing.
Quick Answer
The correct answer is a bucket policy statement that uses a Deny effect with a condition checking both `s3:x-amz-server-side-encryption` equals `aws:kms` and the `s3:x-amz-server-side-encryption-aws-kms-key-id` is not null, effectively enforcing SSE-KMS with a specific customer-managed key. This works because the Deny statement explicitly blocks any PUT request that fails to meet both conditions—requiring the encryption header to be `aws:kms` and the KMS key ID to be present and match the intended key—while an Allow statement alone would be insufficient to override a request that omits encryption headers entirely. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of S3 bucket policy enforcement for encryption at rest, a common topic in data security questions. A frequent trap is forgetting that a Deny with `StringNotEquals` on the encryption type must be paired with a `Null` condition on the key ID, otherwise requests with a different KMS key could slip through. Memory tip: think "Deny if not KMS and no key ID" to remember both conditions are required.
DEA-C01 Data Security and Governance Practice Question
This DEA-C01 practice question tests your understanding of data security and governance. 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 data engineer needs to ensure that an Amazon S3 bucket used for sensitive data is encrypted at rest using a customer-managed AWS KMS key. The bucket policy must enforce encryption for all PUT requests. Which policy statement should be added to the bucket policy?
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
{"Effect":"Deny","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"StringNotEquals":{"s3:x-amz-server-side-encryption":"aws:kms"},"Null":{"s3:x-amz-server-side-encryption-aws-kms-key-id":"true"}}}
Option C is correct because it uses a Deny effect with a condition that blocks PUT requests unless the encryption header specifies 'aws:kms' (SSE-KMS) AND the KMS key ID matches the required customer-managed key. The combination of StringNotEquals on the encryption type and Null on the key ID ensures that any request not using the specified KMS key is denied, enforcing both encryption at rest and the use of the customer-managed key.
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.
- ✗
{"Effect":"Deny","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"Null":{"s3:x-amz-server-side-encryption":"true"}}}
Why it's wrong here
This denies unencrypted requests but does not enforce the specific KMS key.
- ✗
{"Effect":"Allow","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"StringEquals":{"s3:x-amz-server-side-encryption-aws-kms-key-id":"arn:aws:kms:us-east-1:123456789012:key/abc123"}}}
Why it's wrong here
This allows requests with the specific key but does not deny unencrypted requests.
- ✓
{"Effect":"Deny","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"StringNotEquals":{"s3:x-amz-server-side-encryption":"aws:kms"},"Null":{"s3:x-amz-server-side-encryption-aws-kms-key-id":"true"}}}
Why this is correct
This denies if encryption is not aws:kms or if the key ID is not provided, enforcing the required encryption.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
{"Effect":"Deny","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"StringNotEquals":{"s3:x-amz-server-side-encryption-aws-kms-key-id":"arn:aws:kms:us-east-1:123456789012:key/abc123"}}}
Why it's wrong here
This denies only if the key does not match, but allows unencrypted requests because the condition is not checked when the header is missing.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose a simple Deny on a missing encryption header (Option A) without realizing that it does not enforce the use of a specific KMS key, or they mistakenly use an Allow effect (Option B) which cannot block non-compliant requests due to the default Allow behavior of S3 bucket policies.
Detailed technical explanation
How to think about this question
The bucket policy uses the 's3:x-amz-server-side-encryption' condition key to check for the encryption type (e.g., 'aws:kms' for SSE-KMS) and 's3:x-amz-server-side-encryption-aws-kms-key-id' to verify the specific KMS key ARN. The Null condition checks if the key ID is absent, which combined with StringNotEquals on the encryption type ensures that only requests with the exact required KMS key are allowed. In practice, this policy is critical for compliance scenarios where data must be encrypted with a specific key managed by the organization, such as in healthcare or financial applications.
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.
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FAQ
Questions learners often ask
What does this DEA-C01 question test?
Data Security and Governance — This question tests Data Security and Governance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: {"Effect":"Deny","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"StringNotEquals":{"s3:x-amz-server-side-encryption":"aws:kms"},"Null":{"s3:x-amz-server-side-encryption-aws-kms-key-id":"true"}}} — Option C is correct because it uses a Deny effect with a condition that blocks PUT requests unless the encryption header specifies 'aws:kms' (SSE-KMS) AND the KMS key ID matches the required customer-managed key. The combination of StringNotEquals on the encryption type and Null on the key ID ensures that any request not using the specified KMS key is denied, enforcing both encryption at rest and the use of the customer-managed key.
What should I do if I get this DEA-C01 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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Last reviewed: Jun 11, 2026
This DEA-C01 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 DEA-C01 exam.
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