protected static function loadKeyFile(string $filePath) : HiddenString
{
$fileData = \file_get_contents($filePath);
if ($fileData === false) {
throw new Alerts\CannotPerformOperation('Cannot load key from file: ' . $filePath);
}
$data = \Sodium\hex2bin($fileData);
\Sodium\memzero($fileData);
return new HiddenString(self::getKeyDataFromString($data));
}