The correct answer is to modify the KMS key policy to allow the specific IAM roles to use the key and attach an IAM policy to those roles granting kms:Encrypt and kms:Decrypt. This two-step approach works because AWS KMS uses a key policy as the primary access control mechanism for a customer managed key; without an explicit allow in the key policy, no IAM policy can grant access to the key. For controlling KMS key access for RDS encryption, the key policy acts as a resource-based policy that defines who can manage or use the key, while an IAM policy on the role provides the user-based permissions. On the AWS Certified Security Specialty SCS-C02 exam, this question tests your understanding of the interplay between key policies and IAM policies, with a common trap being that IAM policies alone are insufficient if the key policy does not explicitly allow the principal. Remember the memory tip: “Key policy first, IAM policy second—without the key policy’s nod, the IAM policy is unheard.”
SCS-C02 Data Protection Practice Question
This SCS-C02 practice question tests your understanding of data protection. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 is using Amazon RDS for PostgreSQL with encryption at rest using AWS KMS. The security team wants to ensure that only a specific set of IAM roles can manage the KMS key used for encryption. Which TWO steps should the team take?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Attach an IAM policy to the IAM roles that grants kms:Encrypt and kms:Decrypt
Option B (Modify the KMS key policy to allow specific IAM roles to use the key) and Option C (Attach an IAM policy to the roles granting kms:Encrypt and kms:Decrypt) are correct. KMS key policies control who can use the key, and IAM policies grant permissions to roles. Option A is wrong because RDS does not use an S3 bucket policy. Option D is wrong because only the key policy can grant kms:Decrypt; IAM policies alone cannot if the key policy restricts. Option E is wrong because VPC endpoints are for network access, not permissions.
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.
✓
Attach an IAM policy to the IAM roles that grants kms:Encrypt and kms:Decrypt
Why this is correct
IAM policies can grant permissions if the key policy allows it.
Related concept
Read the scenario before looking for a memorised answer.
✓
Modify the KMS key policy to allow the specific IAM roles to use the key
Why this is correct
Key policies are the primary control for KMS key access.
Related concept
Read the scenario before looking for a memorised answer.
✗
Attach an IAM policy to the IAM roles that grants kms:Decrypt only
Why it's wrong here
The key policy must also allow; this alone is insufficient.
✗
Create an S3 bucket policy to restrict access to the KMS key
Why it's wrong here
S3 bucket policies do not control KMS key access.
✗
Use a VPC endpoint policy to restrict access to the KMS key
Why it's wrong here
VPC endpoint policies control access through endpoints, not IAM roles.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 SCS-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Data Protection — This question tests Data Protection — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Attach an IAM policy to the IAM roles that grants kms:Encrypt and kms:Decrypt — Option B (Modify the KMS key policy to allow specific IAM roles to use the key) and Option C (Attach an IAM policy to the roles granting kms:Encrypt and kms:Decrypt) are correct. KMS key policies control who can use the key, and IAM policies grant permissions to roles. Option A is wrong because RDS does not use an S3 bucket policy. Option D is wrong because only the key policy can grant kms:Decrypt; IAM policies alone cannot if the key policy restricts. Option E is wrong because VPC endpoints are for network access, not permissions.
What should I do if I get this SCS-C02 question wrong?
Identify which SCS-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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