- A
"Condition": {"StringEquals": {"kms:ViaService": "s3.us-east-1.amazonaws.com"}}
Correct. This condition restricts the KMS key to be used only via the S3 service, ensuring that decryption requests must come through S3.
- B
"Condition": {"StringEquals": {"kms:KeySpec": "SYMMETRIC_DEFAULT"}}
Why wrong: Incorrect. kms:KeySpec is not a valid condition key in S3 bucket policies; it is used in KMS key policies or IAM policies for KMS API calls.
- C
"Condition": {"StringEquals": {"kms:ViaService": "s3.us-east-1.amazonaws.com"}}
Why wrong: Incorrect. This condition is identical to A, so it does not provide a distinct constraint. Selecting both A and C would not satisfy the requirement for three distinct conditions.
- D
"Condition": {"StringEquals": {"kms:GranteePrincipal": "arn:aws:iam::123456789012:role/Admin"}}
Why wrong: Incorrect. kms:GranteePrincipal is used in KMS grants, not in S3 bucket policies.
- E
"Condition": {"StringEquals": {"kms:EncryptionContext": {"aws:s3:arn": "arn:aws:s3:::my-bucket"}}}
Correct. This condition uses kms:EncryptionContext to match the specific S3 bucket ARN, ensuring that decryption is allowed only for that bucket.
How to Enforce KMS Key Permissions for S3 Object Decryption Using Bucket Policy
This SCS-C02 practice question tests your understanding of identity and access management. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. A key principle to apply: kms:ViaService. 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 objects in an S3 bucket. The security team wants to ensure that only users with the appropriate KMS key permissions can decrypt objects. Which THREE conditions should be included in the S3 bucket policy to enforce this? (Choose THREE.)
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
"Condition": {"StringEquals": {"kms:ViaService": "s3.us-east-1.amazonaws.com"}}
Options A and E are the only distinct conditions that can be used in an S3 bucket policy to enforce that only users with appropriate KMS key permissions can decrypt objects. kms:ViaService restricts the use of the KMS key to requests coming via the S3 service, and kms:EncryptionContext restricts decryption to requests that include the specific S3 bucket ARN. Option C is identical to A and thus does not provide an additional constraint, making it redundant. Options B and D are not valid condition keys for S3 bucket policies.
Key principle: kms:ViaService
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
"Condition": {"StringEquals": {"kms:ViaService": "s3.us-east-1.amazonaws.com"}}
Why this is correct
Correct. This condition restricts the KMS key to be used only via the S3 service, ensuring that decryption requests must come through S3.
Related concept
kms:ViaService
- ✗
"Condition": {"StringEquals": {"kms:KeySpec": "SYMMETRIC_DEFAULT"}}
Why it's wrong here
Incorrect. kms:KeySpec is not a valid condition key in S3 bucket policies; it is used in KMS key policies or IAM policies for KMS API calls.
- ✗
"Condition": {"StringEquals": {"kms:ViaService": "s3.us-east-1.amazonaws.com"}}
Why it's wrong here
Incorrect. This condition is identical to A, so it does not provide a distinct constraint. Selecting both A and C would not satisfy the requirement for three distinct conditions.
- ✗
"Condition": {"StringEquals": {"kms:GranteePrincipal": "arn:aws:iam::123456789012:role/Admin"}}
Why it's wrong here
Incorrect. kms:GranteePrincipal is used in KMS grants, not in S3 bucket policies.
- ✓
"Condition": {"StringEquals": {"kms:EncryptionContext": {"aws:s3:arn": "arn:aws:s3:::my-bucket"}}}
Why this is correct
Correct. This condition uses kms:EncryptionContext to match the specific S3 bucket ARN, ensuring that decryption is allowed only for that bucket.
Related concept
kms:ViaService
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
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
- kms:ViaService
- kms:EncryptionContext
- S3 bucket policy conditions for KMS
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
kms:ViaService
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 kms:ViaService, then practise related SCS-C02 questions on the same topic to reinforce the concept.
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Identity and Access Management — study guide chapter
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FAQ
Questions learners often ask
What does this SCS-C02 question test?
Identity and Access Management — This question tests Identity and Access Management — kms:ViaService.
What is the correct answer to this question?
The correct answer is: "Condition": {"StringEquals": {"kms:ViaService": "s3.us-east-1.amazonaws.com"}} — Options A and E are the only distinct conditions that can be used in an S3 bucket policy to enforce that only users with appropriate KMS key permissions can decrypt objects. kms:ViaService restricts the use of the KMS key to requests coming via the S3 service, and kms:EncryptionContext restricts decryption to requests that include the specific S3 bucket ARN. Option C is identical to A and thus does not provide an additional constraint, making it redundant. Options B and D are not valid condition keys for S3 bucket policies.
What should I do if I get this SCS-C02 question wrong?
Review kms:ViaService, then practise related SCS-C02 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
kms:ViaService
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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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