Signature matching

A method for matching a reference signature designated R with a questioned signature designated Q to determine whether the signatures are written by a specified person, said method comprising the following steps:

• a) writing a reference signature on a digitizer or touch-sensitive pad;
• b) digitizing in space and time the reference signature, to give a series of time-related spatial data signals representative of the reference signature beginning with the start of the writing of the reference signature;
• c) writing a questioned signature on a touch sensitive pad;
• d) digitizing in space and time the questioned signature, to give a series of time-related spatial data signals representative of the questioned signature beginning with the start of the writing of the questioned signature;
• e) creating a mapping between points measured at corresponding times in the two signatures to be compared, by matching the measured points that have a maximum correlation between similar areas centered on the measured points on the signatures and simultaneously have a minimum function representative of a curvature of any distortions between similar areas centered on the measured points on the signatures;
• f) quantifying features, including correlation between the areas centered on the measured points in the signatures, the curvature of any distortions, degree of one-to-one mapping between mapped points, and time distortion between the signatures;
• g) minimizing a function which maximizes local correlation, minimizes the curvature of spatial distortion, encourages a one-to-one mapping of points on the respective signatures and minimizes the time distortion;
• and
• h) comparing the quantified features with an accepted criterion of probability that both signatures were written by the specified person and providing an indication of the acceptance or rejection of the signature.