Exam AWS Certified Solutions Architect - Associate SAA-C03 topic 1 question 696 discussion

A key policy is a resource policy for an AWS KMS key. Key policies are the primary way to control access to KMS keys. Every KMS key must have exactly one key policy. The statements in the key policy determine who has permission to use the KMS key and how they can use it.

ACM certificates are for securing communication (e.g., HTTPS/SSL), not for encrypting data at rest in S3. A and D are out. Between B and C, they both create a separate key for each customer, and both work. So which is more cumbersome, managing S3 policies or managing KMS key policies? Of course the latter one. In B, S3 bucket policy centralizes access rules for all keys, while in C, policies are distributed across individual keys. That's why I decide to choose B.

C looks correct

Actually I think neither B or C is correctly worded. If talking about key policy, should be "Modify the key's policy to grant the IAM user permissions for the kms:GenerateDataKey and kms:Decrypt actions at minimum." If talking about bucket policy, should be "Deny GetObjects of particular customer without condition kms key equals 1234abcd...."

Encryption at rest --> KMS Each customer must be able to access only their data --> KMS Key Policies

B. Here's why this option is the best fit: Server-Side Encryption: Encrypting data server-side with KMS ensures encryption happens transparently within AWS, eliminating the need for complex client-side management and potential security risks associated with user-managed keys. Customer-Specific Keys: Utilizing separate KMS keys for each customer provides granular access control and encryption isolation. Each customer can only decrypt their data using their specific KMS key. S3 Bucket Policy: By denying decryption permissions for all principals except the dedicated customer IAM role in the S3 bucket policy, unauthorized access, even from company employees, is prevented. This aligns with the requirement of customer-specific data access.

Option C From Chapt Option A is incorrect because using ACM certificates is typically for establishing secure communication over HTTPS and doesn't directly relate to encrypting data at rest in S3. Option B is incorrect because while it suggests using AWS KMS keys for encryption, it mentions using S3 bucket policies for access control, which would not be appropriate for controlling decryption permissions. Option D is incorrect because it suggests using ACM certificates for client-side encryption, which is not typically used for encrypting data at rest in S3, and the approach described would not effectively control access to the encrypted data.

Correct answer should be C