Indicates whether Amazon Simple Storage Service (Amazon S3) server-side encryption with Amazon S3 managed keys (SSE_S3), server-side encryption with KMS keys (SSE_KMS), or client-side encryption with KMS customer managed keys (CSE_KMS) is used.
For SSE_KMS and CSE_KMS, this is the KMS key Amazon Resource Name (ARN) or ID.
SSE_KMS
CSE_KMS