Password requested when you recover the backup file in phone/pad, but you didn't set it up initially
Edition of ASUS Backup software : 18.104.22.168202 or higher one provide the option of " No need to set up password when you backup" .
However, when you conduct the factory reset, older edition of ASUS Backup software cannot restore those files without set-up password. As a result, you need to update the ASUS Backup to the latest edition by system update or to download it form Google Play.
Special technique : Try to enter 123