Digital technique to analyze handwritten signatures

Methods for deriving information from handwritten signatures are discussed. The signatures are finite-duration signals and hence are treated as having a finite energy content. They are converted into equivalent discrete-time sequences obtained by sampling them fast enough so that the Nyquist criterion for retention of useful information content is satisfied. Each element of this sequence is a complex number representing a point sampled on the handwritten signature. It is proposed that a signature be characterized by its frequency-domain representation, i.e., the spectrum. The complex-valued time series obtained by sampling the signature is subjected to a discrete Fourier transform (DFT) to obtain coefficients that uniquely represent the discrete-time sequence from which they are derived. The DFT coefficients are also directly related to Fourier series coefficients of a periodic signal whose single period is the finite-duration handwritten-signature signal under consideration. Digital signal-processing techniques are applied to process the signature data