The Wifi password is different from the login password of a router. A wifi password is used to access the tplinkwifi.net network of a Tp-link router whereas the login password is used to access the web interface of a device. You cannot assign the same passphrase to both the Wifi and login password. While changing the wireless settings of a router, you can create a hidden network of your router by enabling the "Hide the SSID" tab.