International Business Machines Corporation

Steven C Gundersen

Thomas K Worthington

Timothy Joseph Chainer

An improved signature verification method using dynamic signature characteristics in the frequency domain. Analysis of a signature in the frequency domain is employed when time domain analysis does not adequately distinguish between true signatures and forgeries. The preferred signature characteristics that are measured are two acceleration components of the pen, and the rate of change of axial pressure on the pen. More specifically, correlation functions operating on a sample and reference signature produce a correlation score. If the total correlation score is in a selected interval, then the above measured characteristics are analyzed in the frequency domain with the magnitude squared coherence function.

Signature verification algorithm

An improved method of signature verification. More specifically, this method maps the values of input measures obtained by comparing a sample signature with a reference signature to a universal scale and combines them to produce a measure of similarity.

Measure of distinguishability for signature verification

A signature verification system includes means for obtaining acceleration data and pressure data related to a given signature and means for comparing that data with reference data previously obtained from an identified signer. The correlations between segments of a reference pressure signal and a sample pressure signal are computed. This process involves successively measuring the correlation as the two segments are shifted with respect to each other. The amount of the shifts that produce the maximum correlations between the pressure signal segments is stored in memory. The corresponding segments of acceleration data are shifted with respect to one another by an amount which is .+-.1 time units of the stored shift values during subsequent correlations of the acceleration data. The overall performance of the signature verification system is improved both in terms of processing time and in error rate as compared to the independent shifting method and in error rate with a minor increase in computation time as compared to the pressure only shifting method.

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Carmel, NY, United States of America

Steven C Gundersen