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AssigneeInternational Business Machines Corporation
InventorsNoel M. Herbst, Chao N. Liu
Estimating the term…
Method and apparatus are disclosed for verifying a sample signature based on comparison of the dynamics of a reference and a sample signature. More particularly, second derivative values of pen displacements (i.e. acceleration) and continuous pressure pattern signals are periodically sampled for both a reference and sample signature and a comparison of these second derivative values and pressure patterns is made. To effect the comparisons the two groups (reference and sample) of both second derivative and pressure pattern signals are segmented and corresponding segments are individually correlated. Successive comparisons of the same segment pairs are performed utilizing successive shifting of the phases between the two segments being correlated to find regions of highest possible correlation. A running account of the maximum cross correlation values for all of the segment pairs of the two signatures are kept. Finally, these maximum values obtained for each segment pair comparison are combined and this resultant correlation value is utilized as a verification indicator.
A method for verifying a signature which comprises producing and storing a plurality of first signal sets, each set comprising a plurality of electrical signals, wherein at least one set represents acceleration forces and another set represents pressure forces, each transmitted by a known signer's hand to a writing instrument during the writing on a writing surface of at least one signature by a known person, producing and storing a plurality of second signal sets each comprising a plurality of electrical signals representative of said acceleration and pressure forces by a putative signer at a different time, segmenting said plurality of first and second signal sets for both the known and putative signatures to facilitate identifying regions of high probable correlation, individually correlating similar segment pairs in corresponding signal sets of said first and second sets representing acceleration components and pressure components respectively, combining the correlation results obtained for all of said regions in all of said sets and utilizing this combined correlation value to produce a resultant correlation level value.
A signature verification method for determining if a putative signer has the same signature as a known signer, said method comprising:
A signature verification system comprising means for periodically sampling and storing electrical signals representative of the acceleration component values imparted to a writing instrument on a writing surface during the writing of the signature, means ink for periodically sampling pressure data concurrently with the sampling of said acceleration component values imparted to said writing instrument on said writing surface, means for performing said sampling and storing operations for both a known and a putative signature, the data being stored as first and second signal sets respectively for said known and putative signatures, means for accessing said acceleration representative signal sets and for said known and putative signatures, for performing a cross-correlation analysis thereon, said last-named means including means for locating areas of high probable correlation, means for totalizing said correlation results for each of said areas of high probable correlation into a total correlation value for said acceleration data from said two signatures, means for modifying said total correlation value as a function of said sampled pressure data to produce a composite total correlation value for the two signatures which is a function of the acceleration and pressure data.
A signature verification system for use with an oriented writing instrument comprising means for periodically sampling and storing electrical signal sets representative of both the x and y acceleration component values and the pressure component values impartes to said oriented writing instrument on a writing surface during the writing of a known and a putative signature, said last named means including analog to digital conversion means wherein said signals are stored in digital format, separate signature comparison and correlation means (SCU) for processing each of said sets of acceleration component values and pressure component values, wherein each of said signature comparison and correlation means includes means for accessing the corresponding digital signal set for said known and putative signatures, means for performing a stepwise cross-correlation analysis thereon, said last named means including means for locating and computing correlation values for areas of high probable correlation, means for totalizing said high probable correlation values into a total correlation result for said two signal sets and means for combining the outputs of each of said signature comparison and correlation means into a final correlation value for the two signatures being compared which is a continuous function of x any y accelerations and pressure.
A signature verification system for use with an unoriented writing instrument comprising means for periodically sampling and storing electrical signal sets representative of two orthogonally disposed acceleration component values and the pressure component values imparted to said unoriented writing instrument on a writing surface during the writing of a known and a putative signature, said last named means including analog to digital conversion means wherein said signals are stored in digital format, a first signature comparison and correlation means (SCU) for processing said sets of pressure component values, wherein said signature comparison and correlation means includes means for accessing the corresponding digital signal set for each of said known and putative signatures, means for performing a stepwise cross-correlation anaylsis thereon, said last named means including means for locating and computing correlation values for areas of high probable correlation, means for totalizing said high probable correlation values into a total correlation result for said two signal sets, a complex signature comparison and correlation means (SCU) for processing each of said sets of acceleration component values including means for accessing the corresponding digital signal sets representative of the two orthogonally disposed acceleration components and treating them as two sets of complex signal sets for said known and putative signatures, means for performing a stepwise cross-correlation analysis thereon in complex format, said last named means including means for locating and computing correlation values for areas of high probable correlation by complex arithmetic, means for converting said complex correlation values into a resultant correlation vector and retaining only the magnitude thereof, means for totalizing said resultant high probable correlation vector magnitudes into a total correlation result for said two signal sets and means for combining the outputs of said two signature comparison and correlation means into a final correlation value for the two signatures being compared which is a continuous function of said orthogonal acceleration components and pressure.
A signature verification system for use with an unoriented writing instrument comprising means for periodically producing electrical signal sets representative of two orthogonally disposed acceleration component values and pressure component values imparted to said unoriented writing instrument on a writing surface during the writing of a known and a putative signature,
Dependencies are inferred from the claim text.