Signature capture/verification systems and methods

• US 5,892,824 A
• Filed: 01/12/1996
• Issued: 04/06/1999
• Est. Priority Date: 01/12/1996
• Status: Expired due to Term

• Current Assignee: Checkmate Electronics, Inc. (International Verifact, Inc.)
• Original Assignee: International Verifact, Inc.
• Inventors: Beatson, Rodney, Riley, Marc J., Kelty, Mark A.
• Primary Examiner(s): CANGIALOSI, SALVATORE A
• Application Number:
  US08/585,591
• Time in Patent Office: 1,180 Days
• Field of Search: 380/23-25, 340/825.34, 382/119
• US Class Current: 713/186
• CPC Class Codes: G06Q 20/3829 involving key management
• 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

A signature device for capture or capture and verification includes a variety of advantageous features including, for example, an ability to work in conjunction with an IC card; an improved angle correction technique; an improved technique for adapting to biometric signature changes; and many other new improvements.

Claims

1. A signature capture and verification device for coupling to a portable IC card carried by a cardholder, the portable IC card including at least one electronic storage element, the signature capture and verification device comprising:

a housing defining a writing surface thereon;

a detecting circuit disposed within the housing for detecting position coordinates of a writing stylus during signing of a signature without requiring continual contact between the writing stylus and the writing surface;

a processor connected to the detecting circuit, the processor providing automatic signature verification based on the detected position coordinates and at least one signature template stored in the electronic storage element; and

a coupling mechanism integrated with the housing, said coupling mechanism for connecting the processor to the electronic storage element, the coupling mechanism allowing the processor to read and write to the electronic storage element,

wherein said processor collects signature signing data during at least some times when the stylus is not in contact with the writing surface.

2. A device as in claim 1 wherein the processor performs the functions of:

(a) receiving signature template information stored within the IC card electronic storage element;

(b) comparing at least one aspect of the received detected position coordinates with the received signature template information; and

(c) generating a verification indication based on the comparison.

3. A device as in claim 1 wherein the writing surface defines an x, y coordinate system, and the processor performs the function of angle correcting the detected position coordinates based upon a line of linear regression minimizing the sum of squares of vertical or horizontal distance between the position coordinates and the line of regression, said angle correcting allowing digital signature capture for a range of different signature orientations at arbitrary angles relative to the x, y coordinate system of said writing surface.

4. A device as in claim 1 wherein the writing surface defines an x, y coordinate system, and the processor performs the function of angle correcting the detected position coordinates by minimizing the sum of squares of perpendicular distances between the position coordinates and a line of regression, said angle correcting allowing digital signature capture for a range of different signature orientations at arbitrary angles relative to the x, y coordinate system of said writing surface.

5. A device as in claim 1 further including means coupled to the processor for wirelessly communicating data to a host.

6. A device as in claim 1 wherein the detecting circuit includes a digitizer located beneath and spaced apart from the writing surface, and circuitry coupled to the digitizer for locating the position of the stylus device moving on the surface or on a record member located on the surface.

7. A device as in claim 1 further including means for locating the record member on the writing surface such that the plane of a record member coincides with that of the x,y plane of the detecting circuit during the writing of the signature.

8. A device as in claim 1 further including means for enabling a record member to be inserted easily into position onto the writing surface from the top or from the side and to avoid the member moving on the surface when the signature is written with the stylus device.

9. A device as in claim 1 wherein the stylus device is coupled electrically by a cable to the detecting circuit.

10. A device as in claim 9 wherein the stylus device delivers ink to a writing medium.

11. A device as in claim 9 wherein the stylus device comprises a non-ink cartridge to write "invisibly" directly on the writing surface.

12. A device as in claim 1 wherein the coupling mechanism includes an integrated IC (smart) card connector controlled by the processor such that data including an electronic signature image may be read from and/or written to an intelligent or memory based IC card.

13. A device as in claim 1 further including means for two-way communication with a host device so that a signature captured electronically may be compared with that stored on the IC card or at the host device and may be communicated to the host together with the result of the signature comparison for display, storage, onward transmission or hard copy reproduction.

14. A device as in claim 1 wherein the processor performs the function of comparing a submitted signature against a signature verification template supplied from the host or from the IC card based upon the extraction of a number of mathematically defined features.

15. A device as in claim 1 wherein the processor performs the function of authenticating a verification template against tampering by means of writing a template authentication code into the signature verification template at creation and update and by checking the authentication code when the template is communicated thereto.

16. A device as in claim 1 wherein the processor performs the function of conditionally updating a verification template so that the template molds itself to the author if the signature changes gradually over time.

17. A device as in claim 1 wherein the processor performs the function of enrolling new authors through checking for compatibility of a minimum of three initial signatures.

18. A device as in claim 1 wherein the device further includes a communications port, and the processor performs the function of automatically detecting the host communications protocol and adapting the communications port accordingly.

19. A device as in claim 1 including means for operating wirelessly allowing portability from one location to another.

20. A device as in claim 1 wherein the processor includes means for determining the angle of submission of the signature and correcting for said angle before signature comparison to provide digital signature capture for a range of different signature orientations at arbitrary angles relative to the x, y coordinate system of said writing surface.

21. A device as in claim 1 wherein the processor includes means for calculating the angle of submission which minimizes the sum of squared errors perpendicular to the line of regression through iterative solution of a cubic to allow digital signature capture for a range of different signature orientations at arbitrary angles relative to the x, y coordinate system of said writing surface.

22. A device as in claim 1 wherein the processor includes a data compressor that compresses a captured signature by iteratively reducing the number of points defining the signature until said digital signature is compressed down to a predetermined target size.

23. A device as in claim 1 wherein the processor includes means for encrypting the captured signature using a transaction based number communicated to the device from the host prior to communicating the signature back to the host.

24. A device as in claim 1 wherein the processor includes means for decrypting the signature when supplied with the encrypted signature and the original transaction based number from an attached host.

25. A device as in claim 1 further including a PIN pad allowing PIN based cardholder authentication to take place supporting DUKPT (derived unique key per transaction) and Master Session key management.

26. A device as in claim 1 further including an integrated LCD display coupled to the processor allowing the electronically captured signature to be displayed on said LCD.

27. A device as in claim 1 wherein the processor includes means for authenticating the validity of an IC card by utilizing public key encryption, using the IC card'"'"'s public key to decrypt a message encrypted by the private key from the card.

28. A device as in claim 1 further including means for storing customization parameters characterizing the operation of signature capture, signature verification, signature compression and signature encryption.

29. A signature capture device as in claim 1 wherein the detecting circuit is at least one of (a) electrically and (b) electromagnetically coupled to the writing stylus.

30. A device as in claim 1 wherein said indicia includes signature image representing data stored in the IC card electronic storage element, and said device includes an electronic display connected to at least the processor, the electronic display rendering an image of the cardholder'"'"'s signature based on the signature image representing data stored in the IC card electronic storage element.

31. A device as in claim 30 wherein the display also renders an image of the cardholder'"'"'s signature based on the detected position coordinates.

32. A device as in claim 1 wherein the processor compresses the detected position coordinates.

33. In a signature verification system of the type including a housing having a writing surface and an integrated portable IC card coupler, a method of verifying a signature comprising:

(a) accessing at least one digital electronic storage element within or coupled to said housing;

(b) reading at least one signature template stored in digital form in the electronic storage element;

(c) acquiring a signature on the writing surface using a writing stylus;

(d) during step (c), detecting position coordinates of said writing stylus relative to the writing surface, including collecting signature signing data during at least some times when the stylus is not in contact with the writing surface;

(e) automatically verifying said signature made by step (c) based on the detected position coordinates and said signature template read from said electronic storage element;

(f) reading digital data representing a visual signature image stored in the electronic storage element in digital form in addition to said template; and

(g) rendering, for purposes of visual comparison, an image of the cardholder'"'"'s signature based on said visual signature image representing digital data.

34. A method as in claim 33 further including transforming said detected signature position coordinates relative to a determined line of regression to allow digital signature capture for a range of different signature orientations at arbitrary angles relative to the x, y coordinate system of said writing surface.

35. A method as in claim 33 further including applying an angle correction technique to said detected position coordinates based on solving a cubic expression to provide digital signature capture for a range of different signature orientations at arbitrary angles relative to the x, y coordinate system of said writing surface.

36. A method as in claim 35 further including determining a regression line defined by m=tanα

such that the sum of square e=Σ

(AiBi)² is minimized, where Ai is a detected position coordinate and Bi is a point defined by projecting the detected position coordinate perpendicular onto a line of regression constructed based at least in part on the detected position coordinates.

37. A method as in claim 33 further including compressing the detected position coordinates by iteratively reducing the number of points defining the signature until said digital signature is compressed down to a predetermined target size.

38. A method as in claim 33 further including displaying a signature image base on the detected position coordinates.