If you have an existing EFS that’s unencrypted, you can encrypt it be creating a snapshot using AWS Backup, and then restoring the file system to a new EFS with encryption. If you choose to restore in a directory in the same file system, it will not be encrypted. It has to be a new EFS. In addition, you’ll be asked to select which encryption key to use. The default key will work, unless you have your own.
