do you mean the network key or the password to gain access to router settings
network key is on the bottom of the modem.. and if youre having trouble loggin on via iPhone, try pressing the shift before every letter press.. as you cant make it stay in Caps.
i had some issues with my BE box saying "cannot join" despite having the right password: the issue was the CAPS LOCK: be sure you respect the case and press the caps lock before each letter you type