An electronic mobile device that includes a controller including at least one processor, for controlling operation of the mobile device, a display coupled to the controller, and a navigational input mechanism coupled to the controller and responsive to user manipulation thereof. The controller, in one input mode, moves a selection marker on a user interface screen on the display in response to user manipulation of the navigational input mechanism, and in a second input mode, authenticates a user of the device in dependence on a sequence of input events resulting from user manipulation of the navigational input mechanism matching a predetermined passcode sequence.