- A
Use a customer managed KMS key with a key policy that grants kms:Decrypt only to the specific IAM role, and configure the S3 bucket policy to allow only that role to access the bucket.
Key policy controls who can decrypt, bucket policy controls access to the object.
- B
Enable automatic key rotation in KMS and assign the key to the IAM role.
Why wrong: Key rotation does not control access; it only changes the underlying cryptographic material.
- C
Configure an S3 bucket policy that denies all users except the specific IAM role.
Why wrong: Bucket policy controls access to the object, not decryption of the object if it is encrypted.
- D
Use S3 default encryption with an AWS managed key and trust the IAM role.
Why wrong: Default encryption with AWS managed key does not restrict decryption to a specific role.
Quick Answer
The correct answer is to use a customer managed KMS key with a key policy that grants kms:Decrypt only to the specific IAM role, and configure the S3 bucket policy to allow only that role to access the bucket. This is the most secure approach because KMS key policies operate independently from S3 bucket policies, creating a defense-in-depth barrier: the key policy directly restricts who can perform the cryptographic decrypt operation, while the bucket policy controls data-plane access to the S3 objects themselves. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of the separation between authorization layers—a common trap is assuming a bucket policy alone can prevent decryption, but without a restrictive key policy, any principal with the key’s decrypt permission can still decrypt the ciphertext. Remember the memory tip: “Key policy locks the lock, bucket policy locks the door”—the key policy is the only way to truly restrict the decrypt action itself.
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 uses AWS KMS to encrypt data at rest in Amazon S3. The security team wants to ensure that only users with a specific IAM role can decrypt objects. What is the MOST secure way to achieve this?
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 customer managed KMS key with a key policy that grants kms:Decrypt only to the specific IAM role, and configure the S3 bucket policy to allow only that role to access the bucket.
Option C is correct because using a KMS key with a key policy that grants decrypt only to the specific IAM role ensures that only that role can decrypt, while the bucket policy restricts who can access the bucket. Option A is wrong because the bucket policy alone cannot control decryption. Option B is wrong because S3 default encryption does not restrict decryption. Option D is wrong because KMS automatic key rotation does not control access.
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.
- ✓
Use a customer managed KMS key with a key policy that grants kms:Decrypt only to the specific IAM role, and configure the S3 bucket policy to allow only that role to access the bucket.
Why this is correct
Key policy controls who can decrypt, bucket policy controls access to the object.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Enable automatic key rotation in KMS and assign the key to the IAM role.
Why it's wrong here
Key rotation does not control access; it only changes the underlying cryptographic material.
- ✗
Configure an S3 bucket policy that denies all users except the specific IAM role.
Why it's wrong here
Bucket policy controls access to the object, not decryption of the object if it is encrypted.
- ✗
Use S3 default encryption with an AWS managed key and trust the IAM role.
Why it's wrong here
Default encryption with AWS managed key does not restrict decryption to a specific role.
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.
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Data Protection — study guide chapter
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Data Protection practice questions
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FAQ
Questions learners often ask
What does this SCS-C02 question test?
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: Use a customer managed KMS key with a key policy that grants kms:Decrypt only to the specific IAM role, and configure the S3 bucket policy to allow only that role to access the bucket. — Option C is correct because using a KMS key with a key policy that grants decrypt only to the specific IAM role ensures that only that role can decrypt, while the bucket policy restricts who can access the bucket. Option A is wrong because the bucket policy alone cannot control decryption. Option B is wrong because S3 default encryption does not restrict decryption. Option D is wrong because KMS automatic key rotation does not control access.
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.
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
1 more ways this is tested on SCS-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 company uses AWS KMS to encrypt data in Amazon S3. The security team needs to ensure that only a specific IAM role can decrypt objects in a particular S3 bucket. What is the most secure way to enforce this restriction?
medium- A.Apply an S3 bucket policy that denies all principals except the IAM role
- ✓ B.Set a KMS key policy that grants kms:Decrypt only to the IAM role
- C.Use S3 access logs to monitor unauthorized decryption attempts
- D.Attach an IAM policy to the role granting kms:Decrypt permission
Why B: Option D is correct because using a KMS key policy with a condition for the IAM role provides fine-grained access control. Option A is wrong because bucket policies alone do not control KMS decryption. Option B is wrong because IAM policies alone can be attached to many principals. Option C is wrong because S3 access logs do not enforce permissions.
Last reviewed: Jun 20, 2026
This SCS-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 SCS-C02 exam.
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