- A
Use a resource-based policy on the KMS key that grants access to the user.
Correct. A resource-based policy (key policy) on the KMS key can directly grant the user permission to decrypt.
- B
Create a KMS grant that allows the user to decrypt the key.
Why wrong: Incorrect. KMS grants are typically used for cross-account or temporary access, not as a primary method for granting same-account user permissions.
- C
Attach an IAM policy to the user that allows kms:Decrypt, and ensure the key policy allows the user's account.
Correct. Attaching an IAM policy to the user that allows kms:Decrypt works if the key policy permits the user's account to use IAM policies.
- D
Add a statement in the S3 bucket policy that allows kms:Decrypt for the user.
Why wrong: Incorrect. S3 bucket policies cannot grant kms:Decrypt; they only specify which KMS keys can be used for S3 operations.
- E
Add a statement in the key policy that allows the IAM role to perform kms:Decrypt.
Why wrong: Incorrect. While a key policy can grant decrypt to an IAM role, this does not directly grant the user permission. The role must be assumed by the user, and the question asks about granting the user directly.
Grant KMS Decrypt Permissions to Users and Roles — IAM and Key Policies | AWS Developer Associate Explained
This DVA-C02 practice question tests your understanding of security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: key Policy. 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 developer is designing a system that uses AWS KMS to encrypt data. Which of the following are valid ways to grant a user permission to decrypt data using a KMS key? (Select TWO.)
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
Use a resource-based policy on the KMS key that grants access to the user.
Options A and C are correct. A resource-based policy (key policy) on a KMS key can directly grant decrypt permission to a user (A). Additionally, you can attach an IAM policy to the user granting kms:Decrypt, provided the key policy allows access from the user's account (C). Option B is incorrect because KMS grants are intended for cross-account or temporary access, not as a primary method for granting user permissions within the same account. Option D is incorrect because S3 bucket policies cannot grant kms:Decrypt. Option E is incorrect because it grants permission to an IAM role, not directly to a user, and the question asks about granting a user permission.
Key principle: Key Policy
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Use a resource-based policy on the KMS key that grants access to the user.
Why this is correct
Correct. A resource-based policy (key policy) on the KMS key can directly grant the user permission to decrypt.
Related concept
Key Policy
- ✗
Create a KMS grant that allows the user to decrypt the key.
Why it's wrong here
Incorrect. KMS grants are typically used for cross-account or temporary access, not as a primary method for granting same-account user permissions.
- ✓
Attach an IAM policy to the user that allows kms:Decrypt, and ensure the key policy allows the user's account.
Why this is correct
Correct. Attaching an IAM policy to the user that allows kms:Decrypt works if the key policy permits the user's account to use IAM policies.
Related concept
Key Policy
- ✗
Add a statement in the S3 bucket policy that allows kms:Decrypt for the user.
Why it's wrong here
Incorrect. S3 bucket policies cannot grant kms:Decrypt; they only specify which KMS keys can be used for S3 operations.
- ✗
Add a statement in the key policy that allows the IAM role to perform kms:Decrypt.
Why it's wrong here
Incorrect. While a key policy can grant decrypt to an IAM role, this does not directly grant the user permission. The role must be assumed by the user, and the question asks about granting the user directly.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Be aware that both key policies (resource-based) and IAM policies (with key policy allowing the account) are valid ways to grant decrypt permission to a user. A common trap is to overlook the key policy as a direct grant or to confuse it with IAM policies.
Detailed technical explanation
How to think about this question
Treat this as a scenario question. Identify the problem, the constraint, and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- Key Policy
- IAM Policy
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
Key Policy
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.
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 |
What to study next
Got this wrong? Here's your next step.
Review key Policy, then practise related DVA-C02 questions on the same topic to reinforce the concept.
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FAQ
Questions learners often ask
What does this DVA-C02 question test?
Security — This question tests Security — Key Policy.
What is the correct answer to this question?
The correct answer is: Use a resource-based policy on the KMS key that grants access to the user. — Options A and C are correct. A resource-based policy (key policy) on a KMS key can directly grant decrypt permission to a user (A). Additionally, you can attach an IAM policy to the user granting kms:Decrypt, provided the key policy allows access from the user's account (C). Option B is incorrect because KMS grants are intended for cross-account or temporary access, not as a primary method for granting user permissions within the same account. Option D is incorrect because S3 bucket policies cannot grant kms:Decrypt. Option E is incorrect because it grants permission to an IAM role, not directly to a user, and the question asks about granting a user permission.
What should I do if I get this DVA-C02 question wrong?
Review key Policy, then practise related DVA-C02 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Key Policy
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 →
Same concept, more angles
2 more ways this is tested on DVA-C02
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. A Lambda function needs to decrypt data encrypted with a customer managed KMS key. Which two permissions are commonly required?
medium- ✓ A.kms:Decrypt on the key
- B.iam:CreateUser on the account
- C.s3:PutBucketAcl on every bucket
- ✓ D.Permission for the Lambda execution role to use the KMS key
Why A: Option A is correct because the Lambda function must have permission to call the kms:Decrypt action on the specific customer managed KMS key to decrypt the data. This permission is granted via a key policy or a grant on the KMS key itself, allowing the Lambda execution role to use the key for decryption operations.
Variation 2. A developer is using AWS Lambda to process sensitive data. The Lambda function needs to access a DynamoDB table that is encrypted with a customer-managed CMK. The developer is using the default Lambda execution role. What must be done to allow Lambda to decrypt the DynamoDB table?
hard- A.Add a policy to the Lambda execution role allowing dynamodb:GetItem.
- ✓ B.Add a policy to the KMS key that allows the Lambda execution role to perform kms:Decrypt.
- C.Configure a VPC endpoint for DynamoDB.
- D.Modify the Lambda function to call KMS Decrypt API.
Why B: Option B is correct because the DynamoDB table is encrypted with a customer-managed CMK. The Lambda execution role must be granted permission to use that key. This is done by adding a statement to the KMS key's key policy that allows the Lambda execution role to perform kms:Decrypt. DynamoDB will then perform the decryption on behalf of Lambda. Option A is incorrect because dynamodb:GetItem alone does not grant KMS decrypt permissions. Option C is incorrect because a VPC endpoint is not related to KMS permissions. Option D is incorrect because Lambda does not need to directly call the KMS Decrypt API; the key policy handles the authorization.
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Last reviewed: Jun 20, 2026
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