private function generateSalt()
    {
        $str = '';
        $length = 64;
        $chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!@#$%^&*(){}[]/|`,.?+-_=:;<> ';
        $count = strlen($chars);
        
        while ($length--) {
            $str .= $chars[mt_rand(0, $count - 1)];
        }
        
        return 'base64:' . base64_encode($str);
    }