DEA-C01 Data Security and Governance Practice Question
A data engineer needs to share an S3 bucket with another AWS account. They want to ensure that the objects in the bucket remain encrypted with SSE-KMS using a customer managed key. What additional step is required for cross-account access?
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
✓
Modify the KMS key policy to grant the target account kms:Decrypt permission
When using SSE-KMS with a customer managed key, cross-account access requires the KMS key policy to grant the target account's IAM role or user the necessary KMS permissions (kms:Decrypt, and optionally kms:GenerateDataKey). The S3 bucket policy must also grant s3:GetObject, and the target account's IAM policy must allow kms:Decrypt. However, the key policy is the additional step specific to KMS that is not covered by S3 policies alone. Without it, the target account cannot use the key. Option A is correct because modifying the key policy is essential. Option B is insufficient because the target account's IAM policy cannot override the key policy. Option C is unnecessary and breaks encryption. Option D provides S3 access but not KMS access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Modify the KMS key policy to grant the target account kms:Decrypt permission
Why this is correct
The KMS key policy must allow the target account to use the key for decryption.
- ✗
Add an IAM policy in the target account to allow kms:Decrypt
Why it's wrong here
The target account's IAM policy is insufficient; the key policy must also allow it.
- ✗
Disable SSE-KMS encryption on the bucket
Why it's wrong here
Disabling encryption would reduce security and is not required.
- ✗
Add a bucket policy that grants the target account s3:GetObject
Why it's wrong here
Bucket policy is needed, but it does not grant KMS decrypt permissions.
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
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DEA-C01 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 DEA-C01 exam.