Abstract

A signature verification system consisting of a durable pressure sensitive data input stylus, signal processing, and computer algorithms for enrollment of signatures and verification. The stylus contains two transducers placed so that axial force and lateral force are measured simultaneously. Combining the two signals at digitized sample points yields a ratio of pressures indicative of the angle of the stylus to the writing surface at that moment, controlling for variations in actual force. The ratio, called a relative angle, is calculated for the entire signal train of a signature and for various simple divisions, or segments. Segments are equal divisions of the signal train by various divisions. While the relative angle of the whole signature may vary unpredictably between signings, the unique variations around the average relative angle form unique signature discriminates. Variations are measured by comparing relative angle measurements of segments, one to another, in all mathematical combinations. The combinations are called measurement points and each measurement point has a value based on the comparison. Some measurement point values, out of many sampled by computer, are uniquely consistent for particular signers. These unique measurement points and their limited ranges of variation are determined during enrollment and become the signature discriminates. These signature discriminate measurement points and values electronically distinguish an enrolled signer. Verification is simplified by comparing only chosen reference measurements to determine if the incoming values fall within the acceptable range of values. An easily adjustable score determines rejection or acceptance of a signature to be verified.