Identification based on handwriting samples

An individual, who is to be subsequently identified, first signs his signature, hereinafter called a template signature, with a special pen, attached to circuits, which produce digital sample signals from which a set of parameters of his signature are derived. This set of template signature parameters is stored in a memory along with sets of parameters derived from template signatures of other individuals. Subsequently, when an individual signs his name with a special pen, the circuits will produce a set of parameters, corresponding to those produced for a template signature. Parameters are selected which can provide strong distinction between signatures. The selected parameters are then used to derive from memory only those sets of template parameters which include the selected parameters which have values falling within a predetermined acceptable range of values. These sets of template parameters are then compared by parameter methods (or, by correlation methods, if the raw signals are available) with the specimen set of parameters to determine the best comparison and thereby provide signature and individual identification.

BACKGROUND OF THE INVENTION 
It is known to verify the signature of a person by comparing that signature 
with a previously produced and stored template signature of that person. 
This is usually done by providing the person, whose signature is to be 
verified, the address in memory wherein the template data set, 
representing the template signature, is stored. The address may be 
memorized and entered via a keyboard into a computer system including the 
memory, or it may be stored on a card which is read. The template data 
set, which is read out, is then compared in some manner with a specimen 
data set derived from the person's signature for verification. 
It would be exceedingly useful if some way could be found whereby the 
signature of a person or even more broadly, a specimen of the handwriting 
of a person, not necessarily his name, could be used not only to verify 
such handwriting but also to identify that person. Hereafter, the word 
signature should be taken to mean a specimen of handwriting constituting a 
predetermined set of words, or a word, or a symbol, and may also include a 
person'5 name. 
OBJECTS AND SUMMARY OF THE INVENTION 
An object of this invention is to provide a method and means of identifying 
a person from his signature. 
Still another object of this invention is the provision of a method and 
means of using predetermined parameters derived from a specimen signature, 
for deriving sets of template parameters including the predetermined 
parameters, from a memory storing a plurality of sets of template 
parameters derived from template signatures. 
Yet another object of this invention is the provision of a novel and useful 
method and means for achieving both signature verification and individual 
identification using the person's signature. 
The foregoing and other objects of the invention may be achieved by storing 
in a memory distinctive data sets, such as parameters sets, each set 
derived from a template signature, which uniquely identifies that 
signature. When a specimen signature is written, parameters which provide 
a strong distinction between signatures are selected. An acceptable range 
of the values of these parameters is established. The contents of the 
memory are then read out and the range of values for the selected specimen 
parameters are compared with similar parameters in the template parameter 
sets. Those template parameter sets containing parameter values which fall 
within the range are then compared with the specimen parameter set. The 
best comparison provides an identification of the individual who provided 
the specimen signature. 
In an application for patent, Ser. No. 629,290, entitled Identification By 
Handwriting Verification, by Hewitt Crane et al., which is assigned to a 
common assignee, there is shown and described a system for deriving and 
comparing the parameters of template and specimen signatures. 
By way of example, one parameter that may be used may be the number of 
times a person lifts his pen from the paper in writing his signature. This 
is called "pen ups". A second parameter may be signature duration. Others 
may be number of zero crossings, etc. 
The novel features of the invention are set forth with particularity in the 
appended claims. The invention will best be understood from the following 
description when read in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 is a block schematic diagram illustrative of how the P, X and Y 
force signals may be generated in writing with a pen for both template and 
specimen signatures, and how for example, signature duration as one 
parameter, may be measured and how the pen-ups, as a second parameter, are 
detected and counted. A pen, of the type suitable for use with this 
invention together with the necessary associated circuitry which will 
generate the X, Y and P signals are described and claimed in U.S. Pat. No. 
3,915,015. A pen 10, and signal generating circuit 12, which is associated 
therewith, produce X, Y and P signals, which are respectively 
representative of the direction forces and pressure. These are analog 
signals which are respectively applied to three sampler circuits, 
respectively 14, 16 and 18. These sampler circuits, are periodically 
enabled to sample the signals applied to their inputs in response to 
pulses received from a free-running oscillator, as will be subsequently 
described. The sample signals, which constitute the outputs of the 
respective sampler circuits 14, 16 and 18 are respectively applied to 
analog to digital converting circuits 20, 22 and 24 (A/D) to provide 
digitized samples. The outputs of the three A/D circuits are transferred 
to "other parameter generating circuits" 25 wich convert the force signals 
into other parameter values. This may be done for example in the manner 
shown and described in a patent application by Crane et al. filed Nov. 6, 
1975, bearing Ser. No. 629,290 and entitled "Identification by Handwriting 
Verification", and assigned to a common assignee. 
The pressure signal provided by the generating circuit 12, is also applied 
to a threshold circuit 26. The threshold circuit measures the amplitude of 
the P signal against a pre-established reference potential, provided from 
a reference potential source 28. If the pressure signal exceeds the 
reference potential signal, the threshold circuit 26 applies an output to 
a threshold pulse generator 30, which produces a single pulse in response 
thereto. The pulse generator output sets a flip flop 32 and is also 
applied to a gate 34, which receives enabling input from the set output of 
the flip flop 32. The output of the gate 34 is applied to a pen-up counter 
36. 
As will be subsequently described, flip flop 32 remains set until the end 
of the signature. Each time the pen 10 is lifted from the paper and, 
within a perdetermined interval, the pen is again applied to the paper, 
pulse generator 30 will provide an additional pulse. Thus, by counting the 
number of pulse outputs from pulse generator 30 during a signature, one 
can determine how many times the pen was lifted during the signature. 
Accordingly, the pen-up counter 36 at the end of the signature will 
contain a total count equal to the number of pen-ups that occur during the 
signature. This is one parameter. 
The set output of flip flop 32 also enables a gate 38. The output of a 
free-running oscillator 39, can then be applied by the gate 38 to a sample 
counter 40, and also to the sampling circuits 14, 16, and 18, whereby they 
can sample the respective X, Y and P input signals. 
The P output of the X, Y and P generating circuit 12 is also applied to an 
inverter 42, the output from which is applied to two And gates, 
respectively 44 and 46. Gate 44 is enabled when flip flop 32 is 
transferred to its set condition. Accordingly, when this occurs the output 
of the inverter 42, in response to a P signal, is applied to a pulse 
generator 47. The pulse generator 47 generates a pulse which is applied to 
a time delay circuit 48. Should an enabling output from the inverter 42 
still be present at the end of the delay, provided by time delay circuit 
48, And gate 46 provides an output which can be considered as an "end of 
signature" output. This is used to reset the flip flop 32. The time delay 
48 establishes an interval between its input and output sufficiently long 
so that pen-ups required for going from one word or one character to 
another or for crossing i's or dotting t's will transpire before that 
interval. Only when the pen has been lifted for a sufficient time to 
indicate that the signature has been terminated is an output received from 
the time delay circuit 48. 
It should be noted that the inverter 42 will provide an output each time 
the pen is lifted from the paper whereby gates 44 and 46 will have a 
signal applied thereto. In the presence of an output from And gate 46, 
flip flop 32 is reset whereby And gates 34 and 38 are no longer enabled. 
The outputs of the sample counter 40 is applied to a set of gates 50, which 
are enabled to transfer the total count of the sample counter, in response 
to an output from And gate 46, to a sample counter register 52, shown in 
FIG. 2. The sample count indicates the time required for writing the 
signature. This may be considered as another parameter. The total count of 
the pen-up counter 36 is also applied to a set of gates 54, to enable them 
to transfer the total count to a pen-up register 56, shown in FIG. 2. 
Referring now to FIG. 2, the output of the And gate 46 and the end of the 
signature signal are applied to an Or gate 58. The output of the Or gate 
is applied to a state counter 60, enabling it to go from a zero to its one 
count state. The one count state of the state counter is applied to an And 
gate 62. The enabling input to the And gate 62 is the output of an 
inverter 64, which, in the absence of an input, enables the And gate 62, 
to apply pulses from a clock pulse source 66, to an address counter 68. 
The inverter 64 is connected to receive the last or nth count of the 
counter 68, so that when that count is reached, which occurs when the last 
storage location in a memory 70 has been read out, the inverter receives a 
signal, whereby no more clock pulses can pass through And gate 62 and the 
address counter 68 no longer addresses the memory 70. 
The memory 70 stores parameter information or a set of parameters for a 
plurality of template signatures. This parameter data is the output of the 
circuits such as "other" parameter generating circuits 25, pen-ups from 
the pen-up counter 36, as well as sample counts from sample counter 40. 
This data is stored at a plurality of locations in memory 70 which can be 
addressed by address counter 68. 
Either part of the same memory, or a supplemental memory 72, may be used 
for storing, at locations corresponding to those in memory 70, data which 
when read out is displayed by a display device 74. This display is in 
human readable form and enables identification of the template parameters 
sets selected for comparison with the specimen parameter set, from which, 
as will be shown, identification of the person who provided the specimen 
signature can be made. 
The memory 70, in response to being addressed by the address counter 68, 
transfers the parameter set at the addressed location into a register 76. 
So much of the register as contains the parameters, which are to be 
compared with the specimen parameters are applied to comparator circuits 
78 and 79, to be respectively compared with the pen-up parameter which is 
in the pen up register 56 and the sample count parameter in the sample 
count register 52. 
The comparators 78 and 79 do not look for identical comparisons between its 
two inputs, but rather look for previously determined ranges. This is to 
take care of the situation that a person does not necessarily sign each 
signature identically. 
An And gate 80 is enabled to produce an output only when both comparators 
78 and 79 produce outputs. The same address which is applied by address 
counter 68 to the memory 70, is also applied to And gates 81. Whenever the 
And gate 80 produces an output indicative that the parameters in register 
76 are within the predetermined ranges, it enables And gates 81 to apply 
the address in the address counter 68 to the memory 72. This address 
locates the data which can be visually displayed by display 74 or printed 
out in the same order as received. This display provides the information 
either identifying or enabling the identification of the person whose 
template parameter sets have been selected by the comparators for 
parameter comparison. 
The output of the And gate 80 is also applied through an Or gate 83 to 
advance a counter 82. This counter sequentially applies its counts to a 
plurality of And gates respectively 84, 86 and 84+m. Another required 
enabling input to these And gates is the set output of a flip flop 95. As 
each of these And gates is enabled in sequence, it can apply shift pulses 
from a shift pulse source 90, to the respective shift registers, 
respectively 94, 96, 94+m. The output of Or gate 83 is also used to set 
the flip flop 95. The set output of this flip flop also enables two And 
gates 100 and 102. When enabled, And gate 100 applies shift pulses to the 
register 76 whereby its contents may be transferred out into one of the 
register 94, 96, 94+m. 
And gate 102 enables shift pulses from source 90 to be applied to a counter 
104. This counter has a count capacity equal to the storage capacity of 
any one of the registers 76 and/or 94, 96, 94+m. It counts the number of 
shift pulses which are applied to the register transferring or receiving 
the parameter data. When the counter 104 reaches its last or p count this 
output is used to reset flip flop 95, whereby shift pulses are no longer 
applied to any of the registers 94, 96, 94+m or to register 76. 
As previously described, the last output, n, of the address counter 68 
discontinues further addressing of the memories 70 and 72, and also 
advances the state counter 60 to its second count. The nth or last output 
of the address counter 68, also resets counter 82. 
Each count from the second to the nth count, of the state counter 60 is 
applied through Or gate 83 to set flip flop 95 and also to advance the 
count of counter 82. The set output of flip flop 95 together with the one 
count output from counter 82 enable And gate 84 to apply the shift pulses 
applied to its input from shift pulse source 90 to register 94 to shift 
its contents out and into a comparison system 110. The comparison system 
can be any known system for comparing the parameter signals of a template 
signature with those of a specimen signature. The specimen signature 
parameters are applied to a parameter comparison system 110 from the 
parameter generating circuits 25, shown in FIG. 1 as well as from sample 
count register 52 and pen up register 56. 
Counter 104 again is enabled to count the shift pulses applied to register 
94 by the set output of flip flop 95. Counter 104 will reset the flip flop 
95 when it reaches its p count, which occurs when the full content of the 
register 94 has been transferred out to the parameter comparison system 
110. The system 110 is enabled to commence the operation of comparing 
parameters in response to an output from And gate 112. This And gate 
applies an enabling input to the system 110 in response to the counts 2 
through n from the state counter 60 together with a p count from counter 
104. 
The parameter comparison system may be of the type described and shown in 
the previously mentioned application Ser. No. 629,290. 
Each time the system 110 completes a comparison, it provides an output 
signal indicative of this to the Or gate 58 to advance the state counter 
60 to its next count state. This will cause a transfer into the comparison 
system of the contents of the next one of the registers 94, 96, 94+n. This 
continues until the contents of each register has been successively 
transferred out and compared with the specimen parameter set. The results 
of each successive comparison are applied through the successive And gates 
114, 116, 114+n which are successively enabled by 2, 3-n counts of counter 
60 to the respective displays 124, 126, 124+n. The highest or best 
comparison result which is displayed, may be specifically identified by 
comparing that display with the ones shown in the display 74. Thus, if for 
example, the second signature which has been selected by the comparator 
produces the best comparison result this best result will be displayed in 
the second display 126. The display 74 will have the person identifying 
data displayed in the same order as they are shown in the displays 124, 
126 and 124+n. Thereby the identification of the indiviudal who has signed 
the specimen signature is produced and confirmed. 
In order to determine when the comparison system has completed the 
parameter comparison operation with all of the template signatures which 
have been read out of memory the output from the comparison system 
indicating the end of a comparison is also applied to a flip flop 130 to 
drive it successively from its set to its reset state. The set output of 
this flip flop is applied to a time delay circuit 132 and to an And gate 
134. The time delay circuit 132 output is also applied to the And gate 
134. The reset output of flip flop 130 is applied to an And gate 136 and 
to a time delay circuit 138. The output of this time delay circuit 138 is 
also applied to And gate 136. The outputs of And gates 134 and 136 are 
applied to an Or gate 140 whose output is the system reset signal. 
The delay established by each of the two time delay circuits is slightly 
longer than the time required for comparison system 110 to receive a set 
of template parameters and perform a comparison. Accordingly, assuming 
that an output from the comparison system 110 drives flip flop 130 to its 
set state, if the flip flop is not driven to its reset state by the time 
time delay 132 applies its output to And gate 134, the And gate will pass 
this output to Or gate 140 and the system will be reset. 
However, should an output from the comparison system 110 occur prior to the 
output of time delay 132 then no system reset will occur. Another output 
must be received from comparison system 110 to drive flip flop 130 back to 
its set state before an output occurs from time delay 138, otherwise a 
system reset will occur. 
In the manner described, the end of the comparison activity for all of the 
template parameter sets is detected. 
The system described may be used for correlation of template and specimen 
signature signals, if along with parameter signal storage, provision were 
made to store the analog signals which are generated in writing the 
template and specimen signatures so that when comparators 78 and 79 
indicate an acceptance the analog signals of the template signature read 
out at that time can be compared with the specimen analog signals. 
Alternative to storing analog signals digital signals which are samples of 
the analog signals may be stored and used for correlation purposes in a 
manner shown and described in an application Ser. No. 629,290. 
FIG. 3 illustrates a schematic block diagram of a suitable comparator 
arrangement for comparators 78 and 79. Using comparator 78 for 
illustrative purposes, the contents of pen-up register 56 are applied to 
an adder circuit 150, and to a subtractor circuit 152. The second input to 
adder circuit 150 is a digital number which when added to the number of 
pen-ups sets the upper limit of the range to be selected from the memory 
contents. By way of example, this is indicated as a +3 source 154. The 
second input to the subtractor 152 is a digital value such as that from 
the +3 source 154, which is subtracted from the number of pen-ups, to 
establish the lower limit of the range. The outputs from the respective 
adder and subtractor circuits are respectively transferred into buffer 
circuits 156, 158. 
Buffer circuit 156 applies its output to subtractor circuit 160. Subtracted 
therefrom are the pen-up contents of register 76. The digital number in 
buffer 158 is applied to subtractor circuit 162, to be subtracted from the 
number of pen-ups in register 76. Should the output of subtractor circuit 
160 be positive it indicates that the number of pen-ups in register 76 is 
less than the top of the range, then a positive output is obtained from 
subtractor 160. Should the number of pen-ups in the register 76 be greater 
than the number of pen-ups indicated by the output of buffer 158, then the 
output of subtractor circuit 162 is positive. Accordingly, positive 
outputs from both subtractor circuits respectively 160, 162, are 
indicative of the fact that the number of pen-ups indicated by the 
contents of register 76 fall within the predetermined range of pen-ups. 
The two positive outputs from subtractor circuits 160 and 162 are applied 
to an And gate 164 whereby it can produce an output indicative of the fact 
that the parameters which have been read out of the memory 70 into the 
registers 76 should be transferred into one of the registers 94, 96 or 94+ 
n. 
While the foregoing description has used the "pen-ups" and duration 
parameters for determining which of the stored template parameters should 
be used for the comparing process with a specimen, it will be appreciated 
that this is by way of example, and it should not be held to be a 
limitation upon the invention. Other parameters may be selected and 
several may be used for further reducing the number of template parameter 
sets used for final comparison. Those parameters which are selected should 
be those which provide "strong" separation characteristics between 
signatures. 
Other samples of variables, which can be used are the ratio of pen-up to 
pen-down time, the maximum X signal divided by the maximum Y signal, etc. 
Each one of these is used to define the center of an assignable detection 
range. 
If desired the template parameter sets may be arranged to be stored in a 
memory in a manner so that template parameter sets including predetermined 
ranges of the parameters used for selecting template parameter sets from 
memory are grouped to be called out by a single address. This address is 
generated from the specimen parameter value. This method of storage can 
save search time but increases the hardware required. 
Further, while the embodiment of the invention has been described using 
parameter sets of digital data, other parameters, which are known in the 
art and are used for uniquely identifying a signature may be used in the 
manner described herein without departing from the scope and spirit of the 
claims. 
There has accordingly been described and shown hereinabove a novel and 
useful arrangement for deriving from a memory template data sets each used 
for uniquely identifying a signature, using data derived from a specimen 
signature provided by an individual whereby that individual may be 
identified.