SAA-C03 Design Secure Architectures Practice Question

A healthcare company stores patient records in an Amazon S3 bucket. Compliance requires that every object be encrypted at rest with a key that the company fully controls, including the ability to rotate and immediately revoke access. The security team also needs a record of every time the key is used to decrypt an object. Which encryption configuration should the company implement?

⚠ Common exam trap

The trap here is assuming that any S3 encryption option provides an auditable key usage trail and customer-controlled revocation, when only customer managed KMS keys deliver both.

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 SSE-KMS with a customer managed key in AWS KMS.

The requirement is customer-controlled encryption with the ability to rotate and revoke keys and to audit every decryption. A customer managed key in AWS KMS provides editable key policies, scheduled or on-demand rotation, the ability to disable the key to cut off access, and CloudTrail logging of cryptographic operations. Other S3 encryption options either lack customer key control or lack a per-use audit trail.

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 SSE-C where the customer provides the encryption key on each request.
Why it's wrong here
SSE-C lets the customer supply the key, but AWS does not store it, so the company must manage durability and rotation entirely outside AWS. There is no KMS key policy to revoke access and no CloudTrail entry for each key use, so the per-use audit trail requirement cannot be met with this approach.
✓
Use SSE-KMS with a customer managed key in AWS KMS.
Why this is correct
A customer managed key in AWS KMS gives the company full control over rotation, key policy, and disabling the key to revoke access. Every Encrypt and Decrypt call is logged to AWS CloudTrail, satisfying the audit requirement. This matches all stated compliance needs for controls and visibility over the encryption key.
✗
Use SSE-S3 with the default AWS managed key for the bucket.
Why it's wrong here
SSE-S3 uses an AWS owned key that the customer cannot rotate, disable, or audit directly. It provides encryption at rest but gives no customer control over the key lifecycle and no per-use key usage trail in AWS CloudTrail. This fails both the full-control and the key-usage-auditing requirement, so it is not suitable for the compliance scenario.
✗
Use client-side encryption with an AWS managed key before uploading objects.
Why it's wrong here
Client-side encryption can give control, but using an AWS managed key means the customer still cannot rotate or revoke the key or see its usage events. AWS managed keys are shared across accounts and their policies are not editable, so they do not satisfy the requirement for customer-controlled revocation and key usage logging.

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

Go deeper

SAA-C03 Design Secure Architectures Practice Question

Why each option matters

Option-by-option breakdown

AWS S3 Storage Class Comparison

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