On-line pen input signature verifier PPI (pen-position/pen-pressure/pen-inclination)

An algorithm is proposed for pen-input online signature verification, incorporating pen-position, pen-pressure and pen-inclination trajectories. The algorithm considers the writer's signature as a trajectory of pen-position, pen-pressure and pen-inclination which evolves over time, so that it is dynamic and biometric. Since the algorithm uses pen-trajectory information, it naturally needs to incorporate stroke number (number of pen-ups/pen-downs) variations as well as shape variations. The proposed scheme first generates templates from several authentic signatures of individuals. In the verification phase, the scheme computes a distance between the template and an input trajectory. Care needs to be taken in computing the distance function because: (i) the length of a pen input trajectory may be different from that of a template even if the signature is genuine; (ii) the number of strokes of a pen input trajectory may be different from that of the template, i.e., the number of pen-ups/pen-downs obtained may differ from that of the template even for an authentic signature. If the computed distance does not exceed a threshold value, the input signature is predicted to be genuine, otherwise it is predicted to be forgery. Preliminary experimental results look encouraging.