1. In a portable computer system having an display, a digitizer, and a computer memory, a method of performing authentication comprising: accessing spatial stroke data and pressure data captured by a digitizer of the portable computer system and representing a user-drawn signature wherein respective pressure data is associated with respective spatial stroke data, wherein a display screen of the portable computer system comprises the digitizer; storing the spatial stroke data and pressure data into the computer memory; building a set of first vectors from the spatial stroke data and the pressure data; comparing the first vectors of spatial stroke data and pressure data of the user-drawn signature to stored second vectors based on the spatial stroke data and pressure data of a reference signature for a match; generating an authentication signal upon a match of the first vectors and the second vectors; and provided the authentication signal is generated, allowing a user access to the portable computer system, otherwise prohibiting the user from accessing a portion of the portable computer system.