The correct answer is that the user can decrypt KMS keys only when the request originates from S3 in us-east-1. This is because the IAM policy uses the `kms:ViaService` condition key set to `s3.us-east-1.amazonaws.com`, which restricts the `kms:Decrypt` permission exclusively to requests made through the S3 service in that region, not through direct API calls or other AWS services. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of service-specific condition keys for KMS, a common trap being that the policy does not require an S3 VPC endpoint—it only checks the service origin, not the network path. A strong memory tip is to think of `kms:ViaService` as a “service gatekeeper”: it only lets KMS decryption happen when the request is routed through the specified service, like S3, blocking all other access paths.
SCS-C02 Management and Security Governance Practice Question
This SCS-C02 practice question tests your understanding of management and security governance. 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. 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Decrypt KMS keys when the request originates from S3 in us-east-1.
Option B is correct because the policy allows decrypting KMS keys only when the request comes through S3. Option A is wrong because it requires S3 endpoint. Option C is wrong because the policy is limited to S3. Option D is wrong because there is no resource restriction.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Decrypt KMS keys only for resources in us-east-1.
Why it's wrong here
Resource is '*' and condition only restricts service, not region explicitly.
✓
Decrypt KMS keys when the request originates from S3 in us-east-1.
Why this is correct
Condition specifies S3 service.
Related concept
Static NAT maps one inside address to one outside address.
✗
Decrypt any KMS key from any service.
Why it's wrong here
Condition restricts to S3.
✗
Decrypt only S3 objects.
Why it's wrong here
Action is kms:Decrypt, not s3:GetObject.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related SCS-C02 NAT questions on configuration and troubleshooting.
Management and Security Governance — This question tests Management and Security Governance — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Decrypt KMS keys when the request originates from S3 in us-east-1. — Option B is correct because the policy allows decrypting KMS keys only when the request comes through S3. Option A is wrong because it requires S3 endpoint. Option C is wrong because the policy is limited to S3. Option D is wrong because there is no resource restriction.
What should I do if I get this SCS-C02 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related SCS-C02 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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