ssekmsKeyId

Specifies the KMS key ID (Key ID, Key ARN, or Key Alias) to use for object encryption. All GET and PUT requests for an object protected by KMS will fail if they're not made via SSL or using SigV4. For information about configuring any of the officially supported Amazon Web Services SDKs and Amazon Web Services CLI, see Specifying the Signature Version in Request Authentication in the Amazon S3 User Guide.

Directory buckets - To encrypt data using SSE-KMS, it's recommended to specify the x-amz-server-side-encryption header to aws:kms. Then, the x-amz-server-side-encryption-aws-kms-key-id header implicitly uses the bucket's default KMS customer managed key ID. If you want to explicitly set the x-amz-server-side-encryption-aws-kms-key-id header, it must match the bucket's default customer managed key (using key ID or ARN, not alias). Your SSE-KMS configuration can only support 1 customer managed key per directory bucket's lifetime. The Amazon Web Services managed key (aws/s3) isn't supported. Incorrect key specification results in an HTTP 400 Bad Request error.