Encrypted backup may be used for security.
In most ways, encrypted backup is used the same as ordinary backup. Also see Backup.
To have an encrypted backup, include the bootcode “protect” in the bootloader.
If you don't use persistent home and opt, when changing from ordinary backup to encrypted backup, your files may not be loaded. This may also happen when changing from encrypted backup to ordinary backup.
There are various ways to overcome this.
One option is to use persistent home and opt during the changeover.
Another option is to create a directory in /mnt/sda1 (or another partition), and copy all files you want to save to it, before adding the bootcode protect. After restarting the computer, copy them back.
Also see Backup.