Image analysis – Applications – Personnel identification
Reexamination Certificate
1998-12-18
2001-10-23
Au, Amelia M. (Department: 2723)
Image analysis
Applications
Personnel identification
C382S122000, C382S189000, C382S218000, C713S176000, C380S030000
Reexamination Certificate
active
06307955
ABSTRACT:
BACKGROUND
The present invention relates to document authentication, and more particularly to the utilization of handwritten signatures in connection with electronically stored, transmitted, and retrieved data and documents.
Handwritten pen-on-paper signatures have been the basis of contracts in commerce for hundreds of years, for a variety of reasons, including:
1. The signature and documents are one in the same, being forever bound together by the ink being on the paper;
2. The identity of the signer can be verified after the fact by a trained forensic document examiner who is skilled in the art and science of signature character analysis, and who can testify, be qualified, and be cross-examined in a court of law; and
3. The signer can keep a copy or duplicate original of the contract to deter fraud.
In the continuing development of electronic document storage and retrieval, a recognized need is inclusion of legally effective signatures for creating legally binding electronic records. Early systems addressing this need utilized a simple image of a signature (such as a bit map) being affixed to a document as a picture of a signature. This approach had the disadvantage that the bit map image of the signature is difficult to verify as being directly from the hand of the signer, in that little if any dynamic data is present. Also, an image of a signature can easily be scanned from an existing document or record and improperly inserted into a document as a forgery.
Later systems included computer algorithms for verifying a signature prior to the user being able to sign an electronic document. Problems with this method include the need to enrol the signer into an electronic verification unit of the system prior to use, the potential for errors in the verification algorithm, and the inability to demonstrate the accuracy of verification of a signature to a layperson or in a court of law. Further, the signatures are typically not transportable to systems having different algorithms without loss of data precision.
U.S. Pat. No. 5,544,255 to Smithies et al. Discloses a computer-based system for capturing and verifying a handwritten signature of an electronically stored document by capturing the signature and storing a set of statistical measurements in a signature envelope that can contain a checksum of the document. The measurements can include shape, number of pen strokes, total line length, average stroke length, number of acceleration and deceleration maxima events, the overall time taken to complete the signature, and the pen down time. The system can also contain a database of known signature measurement templates to be compared with a submitted signature to produce a similarity score. The system if Smithies at al. is not entirely satisfactory; for example:
1. The signature envelopes cannot be verified by a forensic document examiner using traditional methods;
2. The signature envelopes are not readily transportable to future systems, being based on arbitrary measurement statistics of the handwritten signatures; and
3. The signature envelopes are ineffective to the extent that they omit information originally contained in the handwritten signature itself.
Thus there is a need for an electronic document signature system that is effective, reliable, easily verifiable, resistant to forgery, and easy to use, and that otherwise overcomes the disadvantages of the prior art.
SUMMARY
The present invention meets this need by providing a system for the electronic capture of signatures, the binding of the signature to a document or data, and means for compression and storage of the signatures. The invention further provides means for authentication after the fact of the signature by a trained forensic document examiner. Thus the system combines the effectiveness of time-proven pen-on-paper methods of commerce with the efficiency of automatic computer operations. The system also allows for the signer to keep a receipt of both the document and the signature as a duplicate original representation.
In one aspect of the invention, the system includes a graphic tablet for signaling position coordinates of a stylus during manual movement thereof relative to a writing surface; a clock circuit for periodically initiating position measurements by the graphic tablet at predetermined fixed time intervals; a first computer processor electrically interfaced with the tablet, the processor being programmed for receiving a multiplicity of the coordinates during the manual movement of the stylus, and storing respective sets of the coordinates in sequential order as an electronic signature while preserving a time relation between coordinates, the electronic signature forming a time history of the stylus movement; and means for verifying the fixed time intervals of the measurements. The system can further include means for comparing the electronic signature with a reference signature, such as by including reference memory for storing an electronic counterpart of the reference signature, and a cross-correlator for evaluating a degree of correspondence between respective time histories of the electronic signature and the electronic counterpart of the reference signature. The reference memory can be electronically interfaced with the first computer processor. Also, or in the alternative, the means for comparing can be implemented as a parallel display of the electronic and reference signatures, each having a cursor positioned along and perpendicular to a line segment thereof and being movable along the signature ion response to operator input.
The electronic signature can have associated therewith a date and time of the handwritten signature. The electronic signature can have further associated therewith an annotation including at least one of a geographic location, a physical address, and an identification string. The first computer processor can be a digital processor, the electronic signature being a digital signature.
The graphic tablet can include the clock circuit. Preferably the time intervals are not greater than 20 milliseconds. More preferably, the time intervals are between 2 milliseconds and 3 milliseconds. The means for verifying the time intervals can include the computer being programmed for determining a ratio of a total elapsed time of the measurements and a total number of the measurements, and comparing the ratio with the predetermined interval. Alternatively, the clock circuit has a certified unalterable time interval, the tablet being implemented for transmitting an encoded certification stamp with the coordinate data, and the computer can be programmed for decoding the certification stamp to verify use of the certified time interval.
The computer can be further programmed for encrypting the time history to a fixed key of arbitrary length, the stored electronic signature being in encrypted form. Preferably the computer is programmed for generating the key as a cryptographic hash function or message digest of the document. Hereafter, the term “cryptographic hash function” is used interchangeably with “message digest” notwithstanding technical differences therebetween.
In another aspect of the invention, a method for electronically signing a document includes the steps of:
(a) progressively capturing a handwritten signature as an ordered sequence of data corresponding to successive coordinates and corresponding timing of stylus movement producing the signature;
(b) storing the data as an electronic signature; and
(c) electronically binding the electronic signature to a stored counterpart of the document.
The step of binding can include the further steps of:
(a) creating an encryption key by generating a cryptographic hash function of the stored counterpart of the document; and
(b) encrypting the electronic signature to the encryption key.
The method can include the further steps of identifying stored instances of the encryption key and erasing each such instance.
In a further aspect of the invention, a method for electronically signing a document includes the steps of:
(a) capturing a handwrit
Stevens David R.
Zank Anthony E.
Au Amelia M.
Dastouri Mehrdad
Sheldon & Mak
Topaz Systems, Inc.
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