The correct answer is: Apply a bucket policy that requires HTTPS using aws:SecureTransport, and enable default encryption with AWS KMS-managed keys (SSE-KMS), assigning key control to the compliance team.

This configuration ensures data is encrypted both in transit and at rest, satisfying PHI regulatory requirements. The aws:SecureTransport condition in the S3 bucket policy enforces HTTPS-only access, which guarantees in-transit encryption. Meanwhile, enabling server-side encryption with KMS keys (SSE-KMS) allows for centralized key management and fine-grained access controls. By granting the compliance team administrative privileges on the KMS key, the organization can meet the requirement that key control remains internal.

The suggestion to enable default encryption using S3-managed keys (SSE-S3), and use a CloudFront distribution with ACM for HTTPS delivery does not satisfy the requirement that the compliance team manage the encryption key. SSE-S3 uses AWS-managed keys that customers cannot directly control, making it non-compliant in regulated scenarios requiring customer-managed keys.

The option to use AWS Certificate Manager to create a public SSL certificate and link it to S3 is flawed because ACM cannot be directly attached to S3 for enforcing HTTPS access without a CloudFront distribution. Moreover, the use of SSE-KMS is acceptable, but the mention of ACM is misleading and does not contribute to S3s encryption-at-rest policies.

The choice to enable HTTPS-only access with SecureTransport and rely on Amazon Macie for classifying and protecting the PHI misunderstands Macie's role. Macie is a tool for discovering and classifying sensitive data, not for encrypting it. It cannot enforce encryption policies or serve as a substitute for KMS key management.

This question is significant because it evaluates your ability to align AWS security services with strict compliance and encryption requirements. These are common in industries like healthcare, finance, and government. The question tests your understanding of both encryption mechanisms and access control via IAM and KMS.

To answer similar questions, look for cues around regulatory control of encryption keysthis often signals a requirement for KMS (not SSE-S3). Also, watch for in-transit encryption requirements, which are almost always addressed by enforcing HTTPS through the aws:SecureTransport condition. Avoid being misled by services like Macie or ACM that dont directly solve encryption-at-rest problems.

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