HANDWRITING AUTHENTICATION TECHNIQUE

• US 3,699,517 A
• Filed: 09/24/1970
• Issued: 10/17/1972
• Est. Priority Date: 09/24/1970
• Status: Expired due to Term

• Current Assignee: James W. Dyche
• Original Assignee: James W. Dyche
• Inventors: Dyche, James W.
• Primary Examiner(s): Robinson, Thomas A.
• Assistant Examiner(s): Cochran, William W.
• Application Number:
  US05/075,135
• Time in Patent Office: 754 Days
• Field of Search: 340/146.3
• US Class Current: 382/122
• CPC Class Codes: G06V 40/30 Writer recognition; Reading and verifying signatures
• CPC Class Codes: G07C 9/35 by means of a handwritten signature

Abstract

Apparatus and method for measuring and computing velocity and acceleration of a pen point and the pen-paper contacts during writing of a signature and comparing derived data with reference data obtained from several prior signatures to determine whether the real time and reference signatures were made by the same person. The variations x(t) and y(t) of pen point coordinates with time and pen-paper contact intervals are obtained from a graphic tablet. Differentiator circuit means derive x and y velocity and acceleration components which are converted from analog to digital form for processing in a digital moment computer. Contact interval and end of signature computers receive pen point contact signals and compute the total time duration of the signature as well as the time duration of each of the first five pen-paper contact intervals normalized to the duration of the entire signature. The outputs of the moment, contact interval, and end of signature computers are sixteen components of a real time signature vector. A reference signature vector comprised of the mean values of sixteen similar components is predetermined from a plurality of prior true signatures, the deviation of each of those mean component values from the corresponding component value in a real time signature is compared with a variation limit value for that component to determine a correlation, and an authentication decision is made based on a minimum number of such correlations.

Claims

1. Apparatus for authenticating a signature comprising transducer means having a writing surface with x and y Cartesian coordinate axes and a stylus engageable with said surface for impressing thereon a real time signature to be authenticated, means for energizing said transducer means, said transducer means having output terminals and being responsive to the engagement of the stylus with said surface for generating at said terminals real time signals corresponding to the number z(t) of contacts of said stylus with said surface and the variations x(t) and y(t) with time of the x and y coordinates of the stylus on said surface during the writing of the signature, means connected to said terminals for deriving signals corresponding to the velocity x(t), y(t) and acceleration x(t), y(t) components of said stylus during the writing of said signature, means responsive to said component signals and to said stylus contact signals for generating a vector representative of said real time signature, means for storing a corresponding reference signature vector derived from the variables z(t), x(t), y(t), x(t), and y(t) of a plurality Of prior signatures of the same person, and means for comparing said real time signature vector with said stored reference vector to authenticate said signature.

2. The apparatus according to claim 1 in which said signature vector generating means comprises means for computing moments of said velocity and acceleration components.

3. The apparatus according to claim 1 in which said signature vector generating means comprises means for computing cross-moments of said velocity and acceleration components.

4. The apparatus according to claim 1 in which said signature generating means comprises means for computing self-moments and cross-moments of said velocity and acceleration components.

5. The apparatus according to claim 2 in which said signature vector generating means also comprises means for determining the duration of the real time signature.

6. The apparatus according to claim 5 in which said signature vector generating means also comprises means for determining the ratio of time duration of each of a predetermined number of stylus-surface contact intervals to the duration of said real time signature.

7. In a system for authenticating a real time signature, written by a person with a stylus, means for measuring the rate of movement of said stylus during writing of the signature, means responsive to the output of said measuring means for computing real time self-moments and cross-moments of stylus movement rates, means for recording data corresponding to the average of such moments of stylus movement rates derived from a plurality of prior signatures written by a person, and means for comparing said real time moments with said recorded data and determining the authenticity of said real time signature.

8. The system according to claim 7 in which said measuring means comprises means for deriving velocity and acceleration components of said stylus movements, said computing means comprising a multiplier adapted to multiply said velocity and acceleration components to produce said moments thereof.

9. The system according to claim 8 with means for determining the time interval required for the writing of said real time signature, and means for dividing the output of said multiplier by the output of said time interval determining means whereby said moments are normalized to signature duration.

10. The system according to claim 7 in which said data recording means comprises a portable coded card, and reader means adapted to read the code on said card and produce a corresponding input to said comparing means.

11. A system for authenticating a test signature comprising transducer means having a writing surface with Cartesian x and y coordinate axes and a stylus engageable with said surface for impressing thereon a test signature to be authenticated, means for energizing said transducer means, said transducer means having output terminals and being responsive to the engagement of the stylus with said surface for generating at said terminals real time signals corresponding to the number z(t) of contacts of said stylus with said surface and the variations x(t) and y(t) with time of the x and y coordinates of the stylus on said surface during the writing of the signature, means connected to said terminals for deriving signals corresponding to the velocity x(t), y(t) and acceleration x(t), y(t) components of said stylus during the writing of said signature, means for converting said velocity and acceleration components to digital form, means for sequentially multiplying each of said digitized components by the other throughout writing of the signature to produce products corresponding to the moments, respectively, of said components, means for cumulatively summing the output of said multiplying means, a clock adapted to produce timing pulses, a couNter responsive to said pulses from said clock and to the duration of the contact of said stylus with said surface during the writing of the signature for generating an output corresponding to the time duration of said signature, divider means connected to the outputs of said cumulative summing means and of said counter for dividing the former by the latter whereby to normalize said moments to the time duration of the signature, memory means preconditioned by a plurality of reference signatures of the same person to produce outputs corresponding to recorded mean values of the normalized moments of said plurality of signatures and to recorded variances greater than the average variations, respectively, between the mean and actual values of each of said normalized moments for said plurality of signatures, subtractor means responsive to the outputs of said divider means and said memory means for producing an output representative of the differences between real time and recorded values of said moments, respectively, comparator means responsive to the outputs of said subtractor means and to the variances in said memory means for determining the number of said differences that exceed said variances, and indicator means responsive to the output of said comparator means for indicating the validity of said real time signature.

12. The system according to claim 11 which includes adder means responsive to the several outputs of said comparator means for summing said numbers and means for comparing the output of said adder means with a preset threshold value to condition said indicator means.

13. The system according to claim 12 with an AND gate connected to the output of said last named comparator means, means for comparing the numbers z(t) of said contacts in said test signature and in a reference signature and producing an output when the former equals the latter, and means responsive to the output of said last named means for enabling said gate.

14. In automatic apparatus, the method of determining whether a newly written signature and a previously recorded signature were made by the same person consisting of the steps of measuring movements of the writing instrument during writing of the signature and deriving therefrom velocity and acceleration of the instrument, calculating self-moments and cross-moments of said velocity and acceleration characteristics, comparing said moments with corresponding moments derived from the previously recorded signature, and generating a signature validation decision based on the degree with which said compared moments match.

15. The method according to claim 14 including the steps of measuring the durations of instrument-writing surface contact intervals and the total signature interval, dividing the durations of a plurality of said contact intervals by the duration of said total signature interval to normalize the former, comparing said normalized contact intervals with corresponding normalized intervals derived from said previously recorded signature, and additionally conditioning said signature validation decision on the degree with which said compared normalized intervals match.

16. The method according to claim 15 including the steps of counting the number of instrument-writing surface contacts in the newly written signature, comparing said number of contacts with a constant equal to the number of said contacts in said previously recorded signature and, further conditioning said signature validation decision on the equality of said constant and said number of contacts in the newly written signature.

17. The method of determining whether a test signature and a plurality of previously written reference signatures were made by the same person consisting of the steps of continuously measuring movements of the pen relative to the writing surface during writing of the test signature and deriving measurements with respect to time of peN-writing surface contacts z(t) and orthogonal coordinates x(t) and y(t) of the pen point, timing the duration u1 of the entire test signature, timing the durations u2 of a plurality of pen-surface contact intervals with respect to the signature duration u1, differentiating orthogonal pen movements x(t) and y(t) and deriving analog velocity x(t), y(t) and acceleration x(t), y(t) variables thereof, converting said analog velocity and acceleration variables to digital form, multiplying the digitized velocity and acceleration variables by each other and deriving a plurality of moments u7 therefrom, calculating the mean values m1, m2 and m7 or corresponding variables u1, u2 and u7, respectively, of said plurality of reference signatures, subtracting the values of said test signature characteristics u1, u2 and u7 from said mean values m1, m2 and m7, respectively, and comparing the differences with respective predetermined variance limits to establish the number of said test signature characteristics which match said mean values, respectively, and indicating signature validation when said number of matches exceed a preset threshold.

18. The method according to claim 17 with the steps of counting the number of pen-surface contacts occurring during writing of the test signature, comparing said number of contacts with a constant equaling the number of such contacts in said reference signatures, conditioning the generation of said validation decision on the requirement that said test signature contacts equal said constant.

19. The method according to claim 18 including the steps of comparing the time duration of the test signature with a constant having a value exceeding the time duration of said reference signature by a predetermined margin, and indicating invalidation of the test signature if the time duration thereof exceeds said last named constant.