An Improved Regional Correlation Algorithm for Signature Verification Which Permits Small Speed Changes Between Handwriting Segments
by J. S. Lew
If two nearly coincident accelerometers on a pen axis measure orthogonal acceleration components perpendicular to this axis, then the regional correlation algorithm for signature verification divides these data into plausible segments, it compares each segment with a corresponding reference, and it combines the results into a global similarity index. The presently used intersegment distance permits certain natural data transformations: (1) translating a segment by small integer multiples of the sampling interval; (2) moving the pen with uniformly larger amplitude throughout a segment; and (3) rotating the pen about its axis between any two segments. We propose a new intersegment distance which permits further natural transformations: (4) translating a segment by a fraction of the sampling interval; and (5) writing at slightly different uniform speed within each segment. The new distance, like the old one, is the minimum of a certain function. We describe an algorithm which computes this minimum.