This DVA-C02 practice question tests your understanding of security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 wants to encrypt data at rest in Amazon S3 using server-side encryption with KMS (SSE-KMS). They want to ensure that only certain IAM roles can decrypt objects. What must be configured?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
KMS key policy to allow the IAM roles to decrypt
Option C is correct because SSE-KMS uses a customer master key (CMK) to encrypt and decrypt S3 objects. The KMS key policy is the primary access control mechanism for a CMK; it must explicitly grant the IAM roles the kms:Decrypt permission. Without this policy statement, even if the IAM roles have a policy allowing kms:Decrypt, they will be denied access because KMS key policies can override IAM permissions when the key policy does not grant access to the account's IAM principals.
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.
✗
IAM role policy to allow kms:Decrypt
Why it's wrong here
IAM policy alone is not enough if the key policy denies all principals.
✗
S3 bucket policy to allow decrypt
Why it's wrong here
S3 bucket policy cannot grant KMS decrypt permissions.
✓
KMS key policy to allow the IAM roles to decrypt
Why this is correct
KMS key policy must grant kms:Decrypt to the specific IAM roles.
Related concept
Read the scenario before looking for a memorised answer.
✗
KMS key policy to allow s3.amazonaws.com to decrypt
Why it's wrong here
S3 service does not need decrypt; the caller does.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume an IAM role policy granting kms:Decrypt is sufficient, forgetting that KMS key policies act as an independent access control layer that can explicitly deny or allow access, and without the key policy granting the role, the IAM policy is ineffective.
Detailed technical explanation
How to think about this question
KMS key policies are resource-based policies that define who can use the CMK. When using SSE-KMS, S3 calls KMS on behalf of the requester, so the requester must have kms:Decrypt permission in the key policy. A common subtlety is that if the key policy uses a default policy (which grants access to the root account), IAM policies alone can control access; however, if the key policy is customized and does not include the IAM roles, those roles are denied even if their IAM policy allows kms:Decrypt. In real-world scenarios, organizations often combine a key policy that grants access to the account's root user with IAM policies to simplify management, but the question explicitly requires that only certain IAM roles can decrypt, necessitating a custom key policy.
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: KMS key policy to allow the IAM roles to decrypt — Option C is correct because SSE-KMS uses a customer master key (CMK) to encrypt and decrypt S3 objects. The KMS key policy is the primary access control mechanism for a CMK; it must explicitly grant the IAM roles the kms:Decrypt permission. Without this policy statement, even if the IAM roles have a policy allowing kms:Decrypt, they will be denied access because KMS key policies can override IAM permissions when the key policy does not grant access to the account's IAM principals.
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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