A computing device comprising: a touch screen user interface (114; 1129) configurable to display a plurality of input keys as a plurality of virtual objects and to change a color of a background of the user interface; a memory (106; 1132); a sensor (116; 1130) configured to monitor a user mannerism when a user inputs an entry on the user interface, wherein the user mannerism is a pupil color; and a processor coupled to the memory, user interface and the sensor, the processor configured to: generate a first configuration of the plurality of input keys on the touch screen user interface for input by the user of a first key of an authentication code, the first configuration having a first color of the background of the user interface; detect, using the touch screen user interface, a first key of the authentication code by a first user input; detect, using the sensor, a first color of a reflection color from the user's pupil during the first user input; after the first user input and the first color have been detected, change the configuration of the plurality of input keys on the touchscreen user interface to a second configuration for input of a second key of the authentication code, wherein the change in configuration comprises a change of location of the plurality of input keys on the touch screen, and a change in color of the background of the user inteface; detect, using the touch screen user interface, a second key of the authentication code by a second user input at the touch screen user interface; detect, using the sensor, a second color of the reflection color from the user's pupil during the second user input, the second color differing from the first color due to the change of configuration; and determine whether to enable access to the computing device based on the detected first key, detected second key and a stored authentication code and based on a comparison of the first color and the second color each to the color of the respective configuration. a touch screen user interface (114; 1129) configurable to display a plurality of input keys as a plurality of virtual objects and to change a color of a background of the user interface; a memory (106; 1132); a sensor (116; 1130) configured to monitor a user mannerism when a user inputs an entry on the user interface, wherein the user mannerism is a pupil color; and a processor coupled to the memory, user interface and the sensor, the processor configured to: generate a first configuration of the plurality of input keys on the touch screen user interface for input by the user of a first key of an authentication code, the first configuration having a first color of the background of the user interface; detect, using the touch screen user interface, a first key of the authentication code by a first user input; detect, using the sensor, a first color of a reflection color from the user's pupil during the first user input; after the first user input and the first color have been detected, change the configuration of the plurality of input keys on the touchscreen user interface to a second configuration for input of a second key of the authentication code, wherein the change in configuration comprises a change of location of the plurality of input keys on the touch screen, and a change in color of the background of the user inteface; detect, using the touch screen user interface, a second key of the authentication code by a second user input at the touch screen user interface; detect, using the sensor, a second color of the reflection color from the user's pupil during the second user input, the second color differing from the first color due to the change of configuration; and determine whether to enable access to the computing device based on the detected first key, detected second key and a stored authentication code and based on a comparison of the first color and the second color each to the color of the respective configuration. generate a first configuration of the plurality of input keys on the touch screen user interface for input by the user of a first key of an authentication code, the first configuration having a first color of the background of the user interface; detect, using the touch screen user interface, a first key of the authentication code by a first user input; detect, using the sensor, a first color of a reflection color from the user's pupil during the first user input; after the first user input and the first color have been detected, change the configuration of the plurality of input keys on the touchscreen user interface to a second configuration for input of a second key of the authentication code, wherein the change in configuration comprises a change of location of the plurality of input keys on the touch screen, and a change in color of the background of the user inteface; detect, using the touch screen user interface, a second key of the authentication code by a second user input at the touch screen user interface; detect, using the sensor, a second color of the reflection color from the user's pupil during the second user input, the second color differing from the first color due to the change of configuration; and determine whether to enable access to the computing device based on the detected first key, detected second key and a stored authentication code and based on a comparison of the first color and the second color each to the color of the respective configuration.