The answer is that the caller must be allowed to use the KMS key for decrypt operations. This is required because when an S3 object is encrypted with SSE-KMS, S3 must call AWS KMS to decrypt the object before returning it to the requester, so a bucket policy granting GetObject alone is insufficient. The KMS key policy must explicitly grant the cross-account caller kms:Decrypt permission, and the caller’s IAM policy must also allow that action on the specific key—without this dual authorization, S3 returns AccessDenied even when the bucket policy permits the read. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding of the layered permission model where S3 and KMS policies must align for cross-account access, and a common trap is assuming the bucket policy is enough. Remember the memory tip: “Bucket says yes, but KMS holds the key—both must unlock the door.”
DVA-C02 Security Practice Question
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.
An S3 bucket policy allows GetObject from another account, but objects encrypted with SSE-KMS still return AccessDenied. Which additional authorization is required?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The caller must be allowed to use the KMS key for decrypt operations
When an S3 object is encrypted with SSE-KMS, the S3 bucket policy granting GetObject access is not sufficient because S3 must also decrypt the object before returning it. The AWS KMS key policy must grant the caller kms:Decrypt permission, and the caller's IAM policy must also allow kms:Decrypt on the specific KMS key. Without this additional KMS authorization, S3 returns AccessDenied even if the bucket policy allows GetObject.
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 caller must be allowed to use the KMS key for decrypt operations
Why this is correct
Correct for the stated requirement.
Related concept
Read the scenario before looking for a memorised answer.
✗
The caller must own the destination VPC
Why it's wrong here
This does not meet the stated requirement as directly as the correct option.
✗
The bucket must enable static website hosting
Why it's wrong here
This does not meet the stated requirement as directly as the correct option.
✗
The object key must end with .kms
Why it's wrong here
This does not meet the stated requirement as directly as the correct option.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume a bucket policy granting s3:GetObject is sufficient for all objects, forgetting that SSE-KMS adds a separate authorization layer via KMS key policies that must explicitly allow the decrypt operation.
Detailed technical explanation
How to think about this question
Under the hood, when S3 receives a GetObject request for an SSE-KMS encrypted object, it calls KMS to decrypt the object's data key using the Decrypt API. The KMS key policy must explicitly grant the cross-account principal kms:Decrypt permission, and the principal must have an IAM policy allowing kms:Decrypt on that key. A common real-world scenario is granting cross-account access to encrypted logs: the bucket policy allows GetObject, but the KMS key policy must also list the consuming account's root or IAM role as a key user.
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 caller must be allowed to use the KMS key for decrypt operations — When an S3 object is encrypted with SSE-KMS, the S3 bucket policy granting GetObject access is not sufficient because S3 must also decrypt the object before returning it. The AWS KMS key policy must grant the caller kms:Decrypt permission, and the caller's IAM policy must also allow kms:Decrypt on the specific KMS key. Without this additional KMS authorization, S3 returns AccessDenied even if the bucket policy allows GetObject.
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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