The correct answer is the bucket policy that denies s3:PutObject unless the request includes the header s3:x-amz-server-side-encryption with the value aws:kms. This works by combining a Deny effect with a condition that checks for the encryption header; if the header is missing or set to any value other than aws:kms, the upload is blocked. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your ability to enforce encryption at rest using customer-managed KMS keys while explicitly rejecting unencrypted uploads—a common trap is confusing SSE-S3 (which uses aws:3) with SSE-KMS (which uses aws:kms). Remember that the Null condition on the header catches requests without any encryption header, while the StringNotEquals condition rejects non-KMS encryption values. A helpful memory tip: "Deny the null, deny the wrong—only aws:kms makes the policy strong."
DOP-C02 Security and Compliance Practice Question
This DOP-C02 practice question tests your understanding of security and compliance. 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 stores sensitive customer data in an S3 bucket. The security team requires that all data be encrypted at rest using customer-managed KMS keys. Additionally, any attempt to upload an unencrypted object must be denied. Which S3 bucket policy should be used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Deny s3:PutObject unless the request includes s3:x-amz-server-side-encryption: aws:kms
Option B is correct because the condition 's3:x-amz-server-side-encryption':'aws:kms' ensures objects are encrypted with KMS, and the Deny statement with 'Null':'s3:x-amz-server-side-encryption':true blocks unencrypted uploads. Option A is wrong because it allows SSE-S3, not KMS. Option C is wrong because it does not deny unencrypted uploads. Option D is wrong because it allows any encryption.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Deny s3:PutObject unless the request includes s3:x-amz-server-side-encryption: true
Why it's wrong here
Allows any encryption, not specifically KMS.
✗
Allow s3:PutObject with condition s3:x-amz-server-side-encryption: AES256
Why it's wrong here
Allows SSE-S3, not KMS.
✗
Allow s3:PutObject with condition kms:EncryptionContext: department:finance
Deny s3:PutObject unless the request includes s3:x-amz-server-side-encryption: aws:kms
Why this is correct
Ensures KMS encryption and denies unencrypted uploads.
Related concept
Standard ACLs match source addresses.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DOP-C02 ACL questions on filtering logic and placement.
Security and Compliance — This question tests Security and Compliance — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Deny s3:PutObject unless the request includes s3:x-amz-server-side-encryption: aws:kms — Option B is correct because the condition 's3:x-amz-server-side-encryption':'aws:kms' ensures objects are encrypted with KMS, and the Deny statement with 'Null':'s3:x-amz-server-side-encryption':true blocks unencrypted uploads. Option A is wrong because it allows SSE-S3, not KMS. Option C is wrong because it does not deny unencrypted uploads. Option D is wrong because it allows any encryption.
What should I do if I get this DOP-C02 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DOP-C02 ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company has an S3 bucket with sensitive data. The security team requires that all data uploaded to the bucket be automatically encrypted at rest using server-side encryption with AWS KMS managed keys (SSE-KMS). How can this be enforced?
easy
A.Enable default encryption on the S3 bucket with SSE-KMS.
✓ B.Use an S3 bucket policy that denies PutObject requests without the x-amz-server-side-encryption header.
C.Enable AWS CloudTrail to monitor uploads and alert on unencrypted objects.
D.Create an IAM policy that requires all S3 operations to use SSE-KMS.
Why B: Option B is correct because S3 bucket policies can deny uploads that do not include the x-amz-server-side-encryption header. Option A is wrong because default encryption applies to objects without encryption headers, but doesn't enforce encryption. Option C is wrong because IAM policies can require encryption but bucket policies are more direct. Option D is wrong because CloudTrail logs actions but does not enforce encryption.
Last reviewed: Jun 20, 2026
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This DOP-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 DOP-C02 exam.
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