The upload fails because the encryption header does not match 'aws:kms'. This occurs because the bucket policy’s first statement explicitly denies PutObject when the `x-amz-server-side-encryption` header is not equal to `aws:kms`; since the application sends `AES256`, the `StringNotEquals` condition evaluates to true, triggering the deny. The second statement, which denies requests with a null encryption header, does not apply here because the header is present. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of how S3 bucket policies enforce specific SSE-KMS encryption on uploads, a common control for compliance. A frequent trap is assuming any encryption header will satisfy the policy, but the condition is strict—only `aws:kms` is allowed. Memory tip: think “KMS or bust”—if the header isn’t exactly `aws:kms`, the policy busts the upload.
SCS-C02 Data Protection Practice Question
This SCS-C02 practice question tests your understanding of data protection. 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 security engineer applies the above S3 bucket policy. An application tries to upload an object with the header "x-amz-server-side-encryption: AES256". What will happen?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The upload fails because the encryption header does not match 'aws:kms'.
Option D is correct. The first statement denies PutObject if the encryption header is not "aws:kms". Since the header is "AES256", it does not equal "aws:kms", so the condition StringNotEquals is true, resulting in a deny. The second statement denies if the header is null; here it is not null, so the second statement does not apply. Thus, the request is denied.
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.
✗
The upload succeeds because the policy allows SSE-S3.
Why it's wrong here
The policy denies non-KMS encryption.
✓
The upload fails because the encryption header does not match 'aws:kms'.
Why this is correct
The first statement denies non-KMS encryption headers.
Related concept
Standard ACLs match source addresses.
✗
The upload succeeds because the object is encrypted.
Why it's wrong here
The policy requires SSE-KMS, not SSE-S3.
✗
The upload fails because the header is missing.
Why it's wrong here
The header is present but not the required value.
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 SCS-C02 ACL questions on filtering logic and placement.
Data Protection — This question tests Data Protection — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The upload fails because the encryption header does not match 'aws:kms'. — Option D is correct. The first statement denies PutObject if the encryption header is not "aws:kms". Since the header is "AES256", it does not equal "aws:kms", so the condition StringNotEquals is true, resulting in a deny. The second statement denies if the header is null; here it is not null, so the second statement does not apply. Thus, the request is denied.
What should I do if I get this SCS-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 SCS-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
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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 security engineer created the above IAM policy for an S3 bucket. What does this policy accomplish?
medium
A.It allows uploading objects with any server-side encryption.
B.It denies uploading objects with SSE-S3 encryption.
✓ C.It denies uploading objects unless they are encrypted with AWS KMS.
D.It requires objects to be encrypted with a specific KMS key.
Why C: Option B is correct. The policy denies PutObject if server-side encryption is not AWS KMS (aws:kms). Option A is incorrect because it allows encryption with any SSE. Option C is incorrect because it denies SSE-S3. Option D is incorrect because the condition is on encryption, not on KMS key ID.
Last reviewed: Jun 20, 2026
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This SCS-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 SCS-C02 exam.
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