SCS-C02 Data Protection Practice Question
A company wants to ensure that data stored in Amazon S3 is encrypted at rest using keys managed by AWS. Which encryption option should they choose?
⚠ Common exam trap
Test-takers frequently confuse SSE-KMS as 'AWS-managed' because KMS can use AWS managed keys, but the question specifically requires keys managed solely by AWS without any customer involvement, which only SSE-S3 provides.
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
✓
Server-side encryption with S3 managed keys (SSE-S3).
SSE-S3 uses AES-256 encryption keys managed entirely by AWS, fulfilling the requirement for encryption at rest with AWS-managed keys. When you upload an object, S3 encrypts it before writing to disk and decrypts it when you access it, all without any customer action or key management overhead.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Client-side encryption.
Why it's wrong here
Client-side encryption is performed by the calling application before the object is transmitted to Amazon S3, so the company controls the keys and the encryption algorithm on its own infrastructure. AWS receives and stores only ciphertext and has no access to the cryptographic keys used to protect the data. This satisfies encryption at rest but would not meet a requirement for AWS to manage the keys, and it imposes additional key lifecycle and application code responsibilities on the company.
- ✗
Server-side encryption with AWS KMS (SSE-KMS).
Why it's wrong here
SSE-KMS encrypts objects at rest but uses an AWS KMS customer-managed key (CMK) whose policy, rotation, deletion, and access permissions are under the customer's administrative control. Unlike SSE-S3, where AWS owns the entire key hierarchy, SSE-KMS requires you to configure IAM/KMS key policies and manage the key lifecycle, and you are billed for each KMS API request used during S3 operations. Therefore, it does not represent the fully service-owned, AWS-managed key scenario.
- ✗
Server-side encryption with customer-provided keys (SSE-C).
Why it's wrong here
SSE-C requires you to include a raw encryption key with every S3 PUT/GET request; S3 uses that key to perform the server-side encryption and then discards the key after the operation. You are solely responsible for storing, rotating, and securely transmitting the keys, and for managing key versions or responding to potential compromise. Because AWS does not hold or continuously manage the keys, this cannot be the option where AWS manages the keys for you.
- ✓
Server-side encryption with S3 managed keys (SSE-S3).
Why this is correct
SSE-S3 uses a multi-layer envelope encryption scheme in which Amazon S3 creates a unique data key for each object and encrypts that data key with a S3-owned master key that AWS automatically rotates. The customer needs no key material, no KMS configuration, and no key lifecycle management, making this the straightforward option for delegating key management entirely to AWS. It is the only option listed that relies purely on AWS-managed keys with no customer-controlled key configuration.
Quick reference
Symmetric Encryption Algorithm Comparison
| Algorithm | Key Size | Block Size | Status | Notes |
|---|---|---|---|---|
| AES-128 | 128-bit | 128-bit | Current standard | NIST approved; WPA3, TLS |
| AES-256 | 256-bit | 128-bit | Current standard | Preferred for sensitive / govt data |
| 3DES | 112-bit effective | 64-bit | Deprecated (2023) | Replaced by AES |
| DES | 56-bit | 64-bit | Broken | Cracked in < 24 h; never deploy |
| ChaCha20 | 256-bit | Stream cipher | Current | TLS 1.3, WireGuard |
Go deeper
Related to this question
About these practice questions
This SCS-C02 question is part of Courseiva's 1,205-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.