Abstract:
A method and system for generating and printing an indicium, such as a postal indicium, on an object such as a mail piece. Other printed material, such as an address block, on the object is scanned, and the scanned image is processed to abstract characterizing information descriptive of the other printed material. Alternatively, the image to be processed can be obtained by filtering the original image wit a print/scan filter which simulates printing and scanning processes. The characterizing information can be text-based or image-based. Image-based characterizing information can be measurements of word lengths, counts of outliers in images of characters, or descriptions of the shape of the other printed material. The characterizing information is combined with other information, such as postal information and the combined information is then cryptographically authenticated with a digital signature or the like. An indicium representative of the authenticated information is then printed on the object. The object&#39;s relationship to the indicium can be verified by regenerating the characterizing information from the other printed material and comparing the regenerated characterizing information with characterizing information recovered from the indicium. Thus, copies of the indicium cannot easily be used, without detection, on other objects which do not include the other printed material

Description:
RELATED APPLICATIONS  
       [0001]     The present application relates to similar subject matter as, and shares elements of disclosure with, commonly assigned application entitled “Method And System For Generating Characterizing Information Descriptive Of Printed Material Such As Address Blocks And Generating Postal Indicia Or The Like Incorporating Such Characterizing Information” (Attorney Docket F-705), filed on even date herewith. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The subject invention relates to the problem of providing a robust, compact characterization of a block of printed text which will distinguish the block of text from other such blocks. More particularly, it relates to the problem of providing a characterization of a printed address block which can be incorporated into a digital postal indicium.  
         [0003]     Postage metering systems account for postage and other values such as parcel delivery service charges and tax stamps, and print indicia representative of such values as proof of payment. To protect against counterfeiting of indicia modern digital postage metering systems use encryption technology. The postage value and other information relating to an indicium are preferably digitally signed, or otherwise cryptographically authenticated, and the information and signature are incorporated into the digital postal indicium.  
         [0004]     Digital postal indicia using encryption technologies are extremely secure. In general, without knowledge of the proper encryption keys, it is essentially impossible to produce a counterfeit digital indicium. However, digital indicia are subject, as are all postal indicia, to “rubber-stamp” counterfeiting where a valid indicium is scanned and reproduced on multiple mail pieces. To prevent such “rubber-stamp” counterfeiting it is known to incorporate information from the address block of the mail piece into the postal indicium. Because space on an envelope is limited, a typically only a small portion of the information in the address block will be incorporated into the indicium.  
         [0005]     In  FIG. 1 , typical prior art mailing system  10  includes address printer controller  12 , address printer  14 , postage meter  16 , and indicia printer  20 . Address printer controller  12  receives address information from a data processing system (not shown), generates a bitmap, and controls address printer  12  to print address block A, representative of the address, on envelope E. Meter  16  receives postage information, and other information, from the data processing system. Meter  16  also receives characterizing information descriptive of block A from address printer controller  12 . The information received can be either text based or image based. Text based information is descriptive of the words or characters making up to the address, (e.g., ASCII code) while image based information is descriptive of the actual printed image in the address block. Meter  16  combines the characterizing information with the postage value and other information, typically digitally signs the combination, generates a bitmap representative of an indicium including the digitally signed combination, and controls indicia printer  20  to print indicium I on envelope E. When the mail piece is received by a postal service the address block can be scanned again, and the information regenerated from the scanned address block compared to information recovered from indicium  1 , thus tying indicium I to the particular mail piece. (Note that since the indicium is cryptographically linked to the address on the mail piece, printer  20  need not be a secure printer; but can be a general purpose printer which can be controlled by other devices for other uses.) Commonly assigned, provisional application “System And Method For Mail Destination Address Information Encoding Protection And Recovery In Postal Payment”, Ser. No. 60/386,868 (Attorney Docket F-520) discloses a system similar to that of the  FIG. 1  using text-based characterizations of the address block.  
         [0006]     While useful for its intended purpose the system of  FIG. 1  and similar systems suffer from the problem that errors caused by the printing and/or the scanning process can cause the system to misrecognize the printed address block and thus fail to recognize a valid indicium. Thus, it is an object of the subject invention to provide a robust and compact, image based method and system for cryptographically linking an indicium to other printed material. (By “robust and compact” herein is meant information which is small enough in quantity to be incorporated into postal indicia yet will identify a text block, and distinguish among text blocks, with sufficient reliability to deter “rubber stamp” counterfeiting; despite errors introduced by the printing and/or scanning processes.)  
       SUMMARY OF THE INVENTION  
       [0007]     The above object is achieved and the disadvantages of the prior art are overcome in accordance with the subject invention by a method and system for generating and printing an indicium on an object. Other information is printed on the object and the system is controlled in accordance with the method to: transform an image of the other printed material in a manner corresponding to the transfer function of printing and scanning of the material to generate characterizing information, the characterizing information being selected to fit within the indicium; cryptographically authenticate the characterizing information and other information; generate the indicium to be representative of the cryptographically authenticated information; and print the indicium on the object. The object&#39;s relationship to the indicium can be verified by regenerating the characterizing information from the other printed material and comparing the regenerated characterizing information with characterizing information recovered from the indicium, and copies of the indicium cannot easily be used without detection on other objects which do not include the other printed material. Methods for transforming the image include scanning the image to generate the characterizing information or by transforming a pristine image with a filter, said filter simulating the transfer function of printing and scanning processes. (By “pristine image” herein is meant an idealized or nominal digital image which is used to control the printer to print the other material, or similar image.)  
         [0008]     In accordance with one aspect of the subject invention the indicium is a postal indicium and the object is a mail piece.  
         [0009]     In accordance with another aspect of the subject invention the other printed material is an address block and the characterizing information includes measurements of word lengths of words comprised in the address block.  
         [0010]     In accordance with another aspect of the subject invention the other printed material is an address block and the characterizing information includes a count of outliers in the address block.  
         [0011]     In accordance with another aspect of the subject invention the other printed material is an address block and the characterizing information includes information which is descriptive of the shape of the address block, or of lines, or of words comprised in the address block.  
         [0012]     Other objects and advantages of the present invention will be apparent to those skilled in the art from consideration of the detailed description set forth below and the attached drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:  
         [0014]      FIG. 1  shows a schematic block diagram of a prior art mailing system.  
         [0015]      FIG. 2  shows a schematic block diagram of a mailing system in accordance with one embodiment of the subject invention.  
         [0016]      FIG. 3  illustrates a method for abstracting characterizing information descriptive of an address block from an image of the address block in accordance with one embodiment of the subject invention.  
         [0017]      FIG. 4  illustrates a method for abstracting characterizing information descriptive of an address block from an image of the address block in accordance with another embodiment of the subject invention.  
         [0018]      FIG. 5  illustrates a method for abstracting characterizing information descriptive of an address block from an image of the address block in accordance with another embodiment of the subject invention.  
         [0019]      FIG. 6  shows a flow diagram of the operation of a secure postal indicia printing system, shown in  FIG. 2 .  
         [0020]      FIG. 7  shows a schematic block diagram of a mailing system in accordance with another embodiment of the subject invention.  
         [0021]      FIG. 8  illustrates a method for abstracting characterizing information descriptive of an address block from an image of the address block in accordance with one embodiment of the subject invention.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0022]     In  FIG. 2 , mailing system  22  includes address printer controller  12 , address printer  14 , Postage meter  16 , and indicia printer  20 , which are substantially similar to the corresponding prior art elements shown in  FIG. 1 . System  22  differs in that address printer controller  12  does not communicate with postal meter  16 , and that scanner  24  scans address block A and scanned data processor  26  generates the characterizing information provided to meter  16  from the scanned image. Together meter  16 , printer  20 , scanner  24 , and processor  26  form secure postal indicia printing system  30 . In one embodiment of the subject invention processor  26  performs an on optical character recognition function and the characterizing information is text based; however embodiments which use image based characterizing information are preferred. Preferably scanner  24  scans address A to generate a bitmap which is processed by processor  26  to generate the characterizing confirmation, as will be described below; however any convenient combination of scanning and processing techniques which provides a digital image and from which suitable characterizing information can be generated can be used. (Use of a separate processor  26  is preferred since it allows the subject invention to be used with an existing postage meter, however it will be apparent to those skilled in art that postage meter  16  can be programmed to implement the functions of processor  26 . Similarly, a single processor can be programmed to manage both control of scanner  24  and processing of the scanned image.) It is believed that more robust results are obtained when the regenerated characterizing information, generated from a scanned image of address block A is compared to characterizing information recovered from indicium I where the recovered information was also generated from a scanned image, rather than from a pristine bit map; and thus includes the inaccuracies and errors introduced into the image by the printing and scanning processes.  
         [0023]     In a preferred embodiment of the subject invention the characterizing information comprises measurements of the lengths of the individual words which make up address A, as shown in  FIG. 3 . Address block A is parsed to identify individual words by first identifying line spaces ls by determining the occurrence of large amounts of horizontal white space between blocks of printed text, and then identifying word spaces ws by determining the occurrence of large amounts of vertical white space between blocks of printed text (as shown with respect the first line of address A). Word lengths /1 through /9 are then determined for address A. Preferably word lengths are taken (measured in pixels) from the edges of word spaces ws (or the address edges) as shown, but can be taken in any convenient manner, such as along the midline of the words.  
         [0024]     As noted the amount of space available in the indicium is limited. Assuming that eight bytes, 64 bits can be allocated to incorporate the characterizing information, and allowing up to four bits for control codes, 60 bits are available to include the characterizing information. (The actual number of bits which can be allocated to express the characterizing information is determined by the size and shape of the postal indicium and the resolution with which the indicium can be printed and scanned.) Table 1 shows the relationship between the number of bits used to encode each word, the number of words which can be encoded, and the granularity (i.e. the number of lengths which can be distinguished) with which the word lengths can be measured.  
                                           TABLE 1                           Bits/Word   2   3   4   5   6   7   8       Number of   30   20   15   12   10   8   7       Encodable       Words       Granularity   4   8   16   32   64   128   256                  
 
         [0025]     It is believed that using four or fewer bits per word would not be useful in postal applications. Thus, in a preferred embodiment, the number of bits used can be selected to encode all words in the address and two control bits will be sufficient to indicate selection of five to eight bits per word to encode the length of the word. In other embodiments, a fixed number of words in the address, for example the first eight, can be scanned at a fixed number of bits per word; eight in this case, since control bits would not be needed to specify the number of bits per word.  
       EXAMPLE  
       [0026]     An address such as shown in  FIGS. 3-5  may, depending on the print font selected, etc., produce the following results using six bits per word:  
                                                                       Word#   1   2   3   4   5   6   7   8   9       Length(pixels)   173   45   150   60   154   103   168   68   189                  
 
 Preferably the absolute lengths are then normalized to the range 1-63, i.e. 2 0 −(2 6 −1), so that the smallest value (45) is mapped to 1 and the largest (189) is mapped to 63 by the relationship: 
 
Normalized length=(63−1)/(189−45)*(length in pixels)−18.375≈0.43*(length in pixels)−18.375, yielding: 
 
                                                                       Word#   1   2   3   4   5   6   7   8   9       Length(normalized)   56   1   46   7   48   26   54   11   63                  
 
         [0027]     The normalized lengths are then encoded into a bit stream, where code 01 indicates six bits per word:  
                           01-111001-000001-101110-000111-110000-011010-1101010-001011-111111-000000                    |    |      |       |        |       |      |       |       |       |               Code Word 1    Word2     Word3    ..............                         Null word          
 
 This bit stream is then incorporated into the indicium to provide a robust and compact characterization of address block A; and, when the indicium is then digitally signed in a conventional manner, will cryptographically link the indicium to the address and associated mail piece. (Note that only bits are included in the actual bit streams of this and other embodiments and other typographic markings are included only for clarity.) 
 
         [0028]     In another embodiment of the subject invention the characterizing information comprises-measurements of the number of “outliers” in each word (or each line) which make up address A, as shown in  FIG. 4 . (By “outliers” herein is meant ascenders or descenders and portions capitals of which project beyond thresholds, which are preferably determined by the upper and lower bounds of lower case letters without ascenders or descenders, such as “a”, “c”, “e”, etc.) Address A is parsed to identify individual words, if necessary, by first identifying line spaces Is by determining the occurrence of large amounts of horizontal white space between blocks of printed text, and then identifying word spaces ws by determining the occurrence of large amounts of vertical white space between blocks of printed text (as shown with respect the first line of address A). Otherwise only the lines need be identified.  
         [0029]     Again assuming six bits are allocated per word, the number of upwards (+) and downwards (−) outliers per word can be encoded as “xxx/yyy” where x and y are binary digits and xxx is the number of (+) outliers and yyy is the number of (−) outliers. Whether outliers are recorded per word or per line can be a predetermined design feature, or pre-set for particular applications or can be program controlled, for example, normally an address block would be characterized by the number of outliers per word, but long addresses could be characterized per line.  
       EXAMPLE  
       [0030]     Again taking eight bytes as the space allocated for the address block characterizing information, as shown in  FIG. 4  with respect to the first address line, (+) outliers  32 , in word  1 ;  34 , in word  2 ; and  36 , in word  3  are identified as exceeding threshold  40 , and outlier  42 , in word  1 , is identified as exceeding threshold  44 . Since for address block A all of the outliers can be encoded in less than 60 bits, the resulting bit stream is:  
                           1-001/001-001/000-100/000-010/000-011/000-001/000-010/000-010/000-101/000-111                   |    |       |        |       |        |       |       |        |        |  |               code word1    word2      word3    word4     word5    word6     word7       word8    word9  end          
 
         [0031]     where code 1 indicates per word characterization and 111 is an end code. (The 111 end code of course implies that no more than six (+) outliers can be recognized in any word, i.e., 110 means 6 or more.) If less space for characterizing information were available in the indicium, the program could recognize that there was insufficient room on a per word basis and the characterizing information could be encoded as “xxxx/yyyy” on a per line basis. The resulting bit stream would be:  
                                       0-1010/0001-1010/0000-1001/0000-1111                           |     |         |         |       |                       code  line1        line2       line3    end          
 
 requiring only 29 bits. (Or allowing a seven line address to be characterized in eight bytes.) This bit stream is then incorporated into the indicium as described above. 
 
         [0032]     In another embodiment of the subject invention, the characterizing information comprises a description of the shape of the address block. The shape is determined by using a conventional “best fit” scanning algorithm which encloses address block A with “best fit” closed curve  50 , as shown in  FIG. 5 . (It should be understood that various algorithms for generating a best fit curve will generate different curves. These differences do not affect the subject invention so long as the same algorithm is used to generate the curve whose description is incorporated into the indicium and to recover the curve from the address block when the indicium is validated.) Preferably, curve  50  is constrained. That is the manner in which a curve can be generated is limited so that the resulting curve is simplified and can be described with limited information. In  FIG. 5 , curve  50  is formed from linked straight line segments, such as segment  51 , which are limited to eight “directions”, up (U), down (D), left (L), right I, up-right (UR), up-left (UL), down-right (DR), and down-left (DL); viewed as being generated starting in the upper left corner of address block A and traveling clockwise around address block A. Preferably, the curve  50  also accounts for spaces between characters, words and lines, treating these spaces as equivalent to printed space, so that curve  50  does not become too convoluted and require extensive descriptive information. It is within the skill of a person skilled in the art to provide an algorithm which will generate robust and compact characterizing information, as described above.  
         [0033]     The characterizing information, i.e., the description of curve  50 , can be encoded in a number of ways. For example, each line segment can be described as a direction and length, preferably in pixels. Lengths can be normalized as described above with respect to  FIG. 3 . Alternatively, end points of line segments, such as end points  52  and  54  of segment  51 , expressed in Cartesian co-ordinates or any convenient co-ordinate system, which is preferably scaled and referenced to address block A to reduce the amount of descriptive information needed, can be used to describe curve  50 . The description, of course, is ultimately sent to meter  16  as a bit stream.  
         [0034]     These methods of encoding have the advantage that they do not require an end code. Processor  26  needs only to detect closure of curve  50 . However, these methods can require relatively large amounts of data if curve  50  is complex. Another method of describing curve  50  is to encode only the directions, without lengths, of each successive line segment.  
       EXAMPLE  
       [0035]     Encoding line segment directions as: 
 
R=000, L=111, U=001, D=110, UR=010, DL=101, DR=011, UL=100; 
 
         [0036]     and starting at the upper left of address block A, curve  50  is described by the bit stream:  
                           000-011-000-010-011-000-001-000-110-000-001-000-110-111-110-000-110-111-110-111-001-111-001-110                    |   |    |   |   |    |   |   |   |    |   |   |    |   |   |   |    |   |   |    |   |   |   |    |               R   DR   R    UR  DR   R    U     R   D    R     U     R   D    L   D    R    D    L   D    L   U   L   D(end)          
 
 Thus curve  50  can be described in nine bytes, including an end code, which can be indicated by reversal (or repetition) of the immediately preceding segment direction. Again, this bit stream is incorporated into the indicium. 
 
         [0037]     In other embodiments, the shape of only a portion of address block, such as a word or line, are described, or only a limited number of line segments are described, which will reduce the amount of data generated. Where only a limited number of segments are described, they can be selected by processor  26  to represent more complex parts of the curve.  
         [0038]     Programming of a data processor to analyze scan data to perform imaging operations such as identifying lines and words, measuring the dimensions of letters and words or fitting a curve to an image in accordance with predetermined constraints are well known. Such operations are substantially routine in the character and general pattern recognition arts, for example. Techniques for carrying out such operations are also taught in:  Handbook of Pattern Recognition and Image Processing,  edited by T Young and K-S Fu, Academic Press, 1986. Thus, programming of scanner  24  and processor  26  to carry out the embodiments described above is well within the ability of those skilled in the art and need not be discussed further here for an understanding of the subject invention.  
         [0039]      FIG. 6  shows a flow diagram of the operation of indicia printing system  30 . At step  60 , scanner  24  scans address block A and sends a digital image, preferably a bit map to image processor  26 . At step  62  processor  26  abstracts characterizing information descriptive of address block A from the image.  
         [0040]     Preferably, the characterizing information is image-based and is generated in accordance with one of the embodiments described above. In other embodiments, processor  26  can perform an OCR function to abstract text based characterizing information. It is believed that by generating text-based characterizing information from a scanned image improved, i.e., more consistent, results will be obtained when the characterizing information is recovered from indicium I and compared with information regenerated from scanning address block A during the validation of indicium I.  
         [0041]     At step  66 , postage meter  16  inputs postal information such as the postage amount, date, etc., from a data processing system (not shown) or other source, and combines it with the characterizing information and digitally signs the combination. Then at step  70 , meter  16  generates indicium I representative of the combined information and digital signature, preferably as a combination of human-readable text and machine-readable binary code such as 2-dimensional bar code. At step  72 , meter  16  printer  20  to print indicium I on mail piece E in a conventional manner.  
         [0042]      FIG. 7  shows mailing system  74  in accordance with another embodiment of the subject invention. System  74  is substantially similar to prior art system  10 , differing in the substitution of printer controller  76 . Controller  76  controls printer  14  to print the address block in a conventional manner but then processes the image to simulate printing and scanning functions before generating the characterizing information.  
         [0043]      FIG. 8  shows a flow diagram of the operation of controller  76 . At step  80 , controller  76  inputs the address block information, and at step  82  generates and prints a digital image representative of the address block in a conventional manner. At step  84 , controller  76  processes the image with a print/scan filter (i.e. a programmed digital filtering algorithm) which simulates the expected transfer function of the printing process used to print the address block and scanning process used by the postal service to regenerate the characterizing information to generate a filtered image which approximates the image which would be produced by scanning the printed address block. (Design of such print/scan filters is well within the ability of those skilled in the art and need not be discussed further here for an understanding of the subject invention.) At step  86  controller  76  abstracts characterizing information from the filtered image in any convenient manner, such as those described above, and at step  90  sends the characterizing information to meter  16 . Use of print/scan filters is advantageous in that their use is transparent to postage meter  16 , and in that the filters can be modified to reflect changes in the printing or scanning processes.  
         [0044]     The embodiments described above and illustrated in the attached drawings have been given by way of example and illustration only. From the teachings of the present application those skilled in the art will readily recognize numerous other embodiments in accordance with the present invention. Accordingly, limitations on the present invention are to be found only in the claims set forth below.