Patent ID: 8723831

Claim:
A portable device comprising: a touch screen that includes a display screen and that generates touch screen data in response to a user's interaction with the touch screen; a processor for executing a security application for authenticating the user to the portable device, wherein the security application includes a plurality of security levels including a first security level and a second security level, the security application including: providing first display data to the touch screen for displaying a security prompt on the display screen; receiving the touch screen data from the touch screen in response to the user's interaction with the touch screen; processing the touch screen data to determine when an authentication shape is recognized as being indicated by the touch screen data, wherein, for the first security level, the authentication shape is recognized based on the at least one of: the size independent shape descriptor and the orientation independent shape descriptor, and wherein, for the second security level, the authentication shape is recognized based on at least one of: a size dependent shape descriptor and an orientation dependent shape descriptor; and authenticating the user to the portable device at the first security level when the authentication shape is recognized based on at least one of: the size independent shape descriptor and the orientation independent shape descriptor; authenticating the user to the portable device at the second security level when the authentication shape is recognized based on at least one of: the size dependent shape descriptor and the orientation dependent shape descriptor; wherein the user's interaction with the touch screen includes a line drawing corresponding to the authentication shape that includes at least one point of self intersection.