It's common to encrypt backups before storing them somewhere to prevent unauthorized access.
To do so you can configure this package to use client-side symmetric zip file password encryption before storing the archive somewhere.
By default you only have to define the BACKUP_ARCHIVE_PASSWORD environment variable in your .env file.
If you want to customize this you can configure the backup.backup.password and backup.backup.encryption keys in your config/backup.php file.
The whole encryption is done with an event listener.
The \Spatie\Backup\Listeners\EncryptBackupArchive listener is attached to the \Spatie\Backup\Events\BackupZipWasCreated event.
The listener is added to the event when both required config keys are not null.
You are free to add this listener your own or override it.
It's important to try this workflow and also to decrypt a backup archive.
So you know that it works and you have a working backup restore solution.
Warning: the default MacOS app to (un)archive ZIPs seems unable to open/extract encrypted ZIP files.
You should use an app like The Unarchiver or BetterZip.