DVA-C02 kms:Decrypt Practice Question
Exhibit
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": "kms:Decrypt",
"Resource": "arn:aws:kms:us-east-1:123456789012:key/abcd1234-a123-456a-a12b-a123b4cd56ef"
}
]
}A developer is trying to decrypt an S3 object using an AWS KMS key. The decryption fails with an 'AccessDenied' error. The IAM policy attached to the developer's user includes the statement in the exhibit. The KMS key policy includes the following statement:
{
"Sid": "Enable IAM User Permissions",
"Effect": "Allow",
"Principal": {
"AWS": "arn:aws:iam::123456789012:root"
},
"Action": "kms:*",
"Resource": "*"
}What is the most likely reason for the failure?
⚠ Common exam trap
Candidates often confuse the required KMS actions for decryption vs. encryption. `kms:GenerateDataKey` is needed to encrypt new objects, while `kms:Decrypt` is needed to decrypt. The key policy default allows root, so it is not the issue.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The developer's IAM policy does not include 'kms:Decrypt' permission.
To decrypt an S3 object encrypted with SSE-KMS, the principal needs kms:Decrypt permission on the KMS key. The key policy's default root statement enables IAM policies in the account, so the most likely cause of AccessDenied is that the developer's IAM policy lacks kms:Decrypt.
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 KMS key policy does not grant access to the developer's IAM user.
Why it's wrong here
This is incorrect because the key policy includes the default statement allowing the root account, which does grant access to IAM users via their IAM policies.
- ✗
The KMS key policy specifies 'kms:*' which is too broad and causes a conflict.
Why it's wrong here
This is incorrect. `kms:*` is a permissive wildcard and does not cause conflicts; it actually grants all actions.
- ✓
The developer's IAM policy does not include 'kms:Decrypt' permission.
Why this is correct
Ly identifies `kms:GenerateDataKey` as the missing permission. For decryption, `kms:Decrypt` is required, not `kms:GenerateDataKey`. However, it is the closest option because it points out a missing KMS action in the IAM policy.
- ✗
The developer's IAM policy uses 'Resource' with the full key ARN but the key policy requires a different format.
Why it's wrong here
This is incorrect. The resource format in IAM policies can be the full key ARN, and the key policy does not require a different format.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
Go deeper
Related to this question
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.