outputEncryptionKmsKeyId    
  The Amazon Resource Name (ARN) of a KMS key that you want to use to encrypt your transcription output.
KMS key ARNs have the format arn:partition:kms:region:account:key/key-id. For example: arn:aws:kms:us-west-2:111122223333:key/1234abcd-12ab-34cd-56ef-1234567890ab. For more information, see  KMS key ARNs.
If you do not specify an encryption key, your output is encrypted with the default Amazon S3 key (SSE-S3).
Note that the role making the request and the role specified in the DataAccessRoleArn request parameter (if present) must have permission to use the specified KMS key.