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Method for signature verification

  • US 5,111,512 A
  • Filed: 05/14/1991
  • Issued: 05/05/1992
  • Est. Priority Date: 05/14/1991
  • Status: Expired due to Term
First Claim
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1. A method for controlling access to a system, the method comprising an initializing step wherein at least one authorized signature is recorded and a recognition step wherein an entrant signature is compared to the authorized signature, wherein:

  • the initializing step comprises the steps of;

    a) digitally recording a multiplicity of authorized sample signature received from digitizing means;

    b) calculating a speed function corresponding to each sample signature, performing pairwise comparisons of the speed functions by applying dynamic time warping (to be referred to as "DTW"), and selecting that signature, to be referred to as a "representative signature," which is most typical according to the DTW calculations;

    c) segmenting the representative signature into individual word features, to be referred to as "letters", based on relatively small local values of the speed function;

    d) segmenting each of the remaining sample signatures into letters by mapping thereupon the segmentation of the representative signature by DTW, such that there is a correspondence between the letters of each pair of segmented sample signatures; and

    e) constructing a reference signature by averaging each set of corresponding letters from the sample signatures; and

    the recognition step comprises the steps of;

    f) digitally recording an entrant signature received from digitizing means;

    g) calculating a speed function for the entrant signature, and segmenting the entrant signature into letters by mapping thereupon the segmentation of the representative signature by DTW such that there is a correspondence between the letters of the entrant signature and the letters of the reference signature;

    h) calculating a dynamic mismatch between the entrant signature and the representative signature by DTW;

    i) calculating a shape mismatch, totalled over all the relevant letters, between the entrant signature and the reference signature;

    j) comparing the dynamic and shape mismatch values to a predetermined acceptance criterion; and

    k) if the acceptance criterion is satisfied, activating an electric circuit such that access to the system is made available.

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