The answer is to add the user’s ARN to the KMS key policy with the kms:Decrypt permission. This is required because KMS evaluates both IAM policies and key policies, but an IAM policy alone cannot grant access unless the key policy explicitly allows it—KMS key policies act as a resource-based gate that must authorize the IAM entity before any IAM permissions are considered. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding of the critical distinction between identity-based and resource-based policies, often appearing as a trap where candidates assume an IAM policy with kms:Decrypt is sufficient. The common mistake is forgetting that KMS defaults to denying access unless the key policy includes the user or account root. Remember the mnemonic: “Key policy first, IAM policy last”—the key policy must open the door before IAM permissions can walk through.
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.
Network Topology
Refer to the exhibit. A developer runs the AWS CLI command to decrypt a file using a KMS key alias 'my-key' and receives the error shown. The developer has an IAM policy that allows 'kms:Decrypt' on 'arn:aws:kms:us-east-1:123456789012:key/abcd1234-...'. Which additional step is required to resolve this error?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add the user's ARN to the KMS key policy with 'kms:Decrypt' permission.
The error occurs because the KMS key policy does not grant the user permission to decrypt using the key. Even though the user has an IAM policy allowing 'kms:Decrypt' on the key, KMS requires that the key policy explicitly allow IAM user permissions (or grant the user direct access) for IAM policies to take effect. By adding the user's ARN to the key policy with 'kms:Decrypt', the key policy grants the necessary access, resolving the error.
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.
✓
Add the user's ARN to the KMS key policy with 'kms:Decrypt' permission.
Why this is correct
The key policy must explicitly grant the user permission to decrypt.
Related concept
Read the scenario before looking for a memorised answer.
✗
Attach a policy to the user that allows 'kms:DescribeKey' on the key.
Why it's wrong here
Decrypt permission is already granted; the missing piece is the key policy.
✗
Use the key ID instead of the alias in the command.
Why it's wrong here
The alias is correctly used; the issue is permissions.
✗
Enable IAM user permissions in the KMS key policy.
Why it's wrong here
That option allows IAM policies to be evaluated, but if it's already enabled, the issue is that the user is not listed.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume IAM policies alone are sufficient for KMS operations, but KMS requires the key policy to explicitly grant access to the user or enable IAM user permissions and then grant the action.
Detailed technical explanation
How to think about this question
KMS uses a dual authorization model: the key policy controls access to the key, and IAM policies can grant additional permissions only if the key policy allows it (via a 'Principal' element or by enabling IAM user permissions). The key policy must explicitly include the user or role as a principal with 'kms:Decrypt' action, or set 'Effect': 'Allow' with a 'Principal' that matches the user's ARN. In real-world scenarios, this often catches developers who assume IAM policies alone suffice, leading to 'AccessDeniedException' errors.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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: Add the user's ARN to the KMS key policy with 'kms:Decrypt' permission. — The error occurs because the KMS key policy does not grant the user permission to decrypt using the key. Even though the user has an IAM policy allowing 'kms:Decrypt' on the key, KMS requires that the key policy explicitly allow IAM user permissions (or grant the user direct access) for IAM policies to take effect. By adding the user's ARN to the key policy with 'kms:Decrypt', the key policy grants the necessary access, resolving the error.
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.
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. Refer to the exhibit. A developer runs the AWS CLI command to decrypt a file using a KMS key. The command fails with an AccessDeniedException. What is the most likely cause?
medium
✓ A.The IAM user 'DevUser' does not have the kms:Decrypt permission on the KMS key.
B.The ciphertext blob is not base64-encoded.
C.The KMS key is disabled.
D.The KMS key ID is incorrect.
Why A: The AccessDeniedException indicates that the IAM user 'DevUser' lacks the required kms:Decrypt permission on the specified KMS key. KMS key policies and IAM policies work together to control access; without an explicit allow for kms:Decrypt on that key, the API call is denied regardless of other permissions.
Variation 2. A developer runs the AWS CLI command to decrypt a file using a KMS key. What is the most likely cause of the error?
medium
A.The encrypted file is corrupted.
B.The CLI cannot read the file.
✓ C.The IAM user lacks kms:Decrypt permission on the key.
D.The KMS key ID is incorrect.
Why C: The IAM user DevUser does not have kms:Decrypt permission on the specified KMS key.
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This DVA-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 DVA-C02 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.