Quick Answer
The answer is the Principal element. This is correct because the Principal element in a KMS key policy explicitly defines which IAM users, roles, or AWS accounts are allowed or denied access to the key, making it the precise tool to restrict decryption to a single IAM role. The Effect, Action, and Resource elements control the outcome, the permitted operations, and the key’s identity, respectively, but only Principal narrows down who can perform those actions. On the AWS Certified Security Specialty SCS-C02 exam, this concept tests your understanding of resource-based policies versus identity-based policies—a common trap is confusing the Action element (which lists operations like kms:Decrypt) with the entity that can perform them. Remember the memory tip: “Principal is the person, Action is the permission, Effect is the verdict.”
This SCS-C02 practice question tests your understanding of infrastructure security. 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.
A company is using AWS Key Management Service (KMS) to encrypt data at rest in Amazon S3. The security team wants to ensure that only a specific IAM role can decrypt the data. Which KMS policy element should be used?
Principal
Specifies the IAM role that can use the key.
Resource
Why wrong: Specifies the key ARN.
Action
Why wrong: Specifies the actions like encrypt and decrypt.
Effect
Why wrong: Specifies whether to allow or deny.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Principal
Option B (Principal) is correct because it specifies who can use the key. Option A (Effect) is for allow/deny. Option C (Action) is for allowed operations. Option D (Resource) is for the key ARN.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Principal
Why this is correct
Specifies the IAM role that can use the key.
Related concept
Standard ACLs match source addresses.
Resource
Why it's wrong here
Specifies the key ARN.
Action
Why it's wrong here
Specifies the actions like encrypt and decrypt.
Effect
Why it's wrong here
Specifies whether to allow or deny.
Common exam traps
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Real-world example
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
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related SCS-C02 ACL questions on filtering logic and placement.
Infrastructure Security — study guide chapter
Learn the concepts, then practise the questions
Infrastructure Security practice questions
Targeted practice on this topic area only
All SCS-C02 questions
1,738 questions across all exam domains
AWS Certified Security Specialty SCS-C02 study guide
Full concept coverage aligned to exam objectives
SCS-C02 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Practise SCS-C02 questions linked to Threat Detection and Incident Response.
Practise SCS-C02 questions linked to Security Logging and Monitoring.
Practise SCS-C02 questions linked to Identity and Access Management.
Practise SCS-C02 questions linked to Management and Security Governance.
Practise SCS-C02 questions linked to Infrastructure Security.
Practise SCS-C02 questions linked to Data Protection.
Practise SCS-C02 questions linked to SCS-C02 fundamentals.
Practise SCS-C02 questions linked to SCS-C02 scenario.
Practise SCS-C02 questions linked to SCS-C02 troubleshooting.
Practice this exam
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Infrastructure Security — This question tests Infrastructure Security — Standard ACLs match source addresses..
The correct answer is: Principal — Option B (Principal) is correct because it specifies who can use the key. Option A (Effect) is for allow/deny. Option C (Action) is for allowed operations. Option D (Resource) is for the key ARN.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related SCS-C02 ACL questions on filtering logic and placement.
Standard ACLs match source addresses.
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 →
Keep practising
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.