April 2, 2007 14:42 World Scientific Review Volume - 9in x 6in Main˙WorldSc˙IPR˙SAB
Issues Involving the Human Biometric Sensor Interface 357
The system in this study accepted all the signatures, and the failure to
enroll rate was 0.0%. In
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and
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they define the “failure to acquire” rate
as the “proportion of attempts for which the system is unable to capture
or locate an image of sufficient quality.” Typically, this is the case when
an individual is unable to present a biometric feature to the device due to
either an injury or to insufficient image quality. As such, this does not apply
to dynamic signature verification because the biometric feature (signature)
is presented by a stylus rather than direct interface with the biometric
sensor. Therefore, a paradox arises between a signature that is repeatedly
signed and acquired by the sensor yet provides an image different to a
normal paper based signature. One subject did have difficulty in providing
a signature that is similar to a pen and paper version; although the system
acquired the image, the signature was thrown out, as it was a statistical
outlier with over 15,000 segments as opposed to 2 to 19 segments exhibited
by other crew members. The failure to acquire rate in this study was
0.0%.
When examining area of the signature across two different digitizers,
the number of pen-up, pen-down sequences should not change significantly
when the signing space is restricted. However, in
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the uptime variable
was significantly different at an α =0.01 level. Durations of the signature,
i.e. the time for individual 0.01 mm groupings, were also significantly
different across these two devices. When the variables associated with the
graphical nature of the signature were examined, there was no significant
difference in the number of variables relating to the signing area of the
device. Area was not a factor in
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, as it was held constant on both
devices; and those variables measuring area, such as distance (p-value =
0.181), net area (p-value = 0.676), and rubber area (p-value = 0.344)
show that there is no statistically significant difference in the signing areas
of the two devices. When two other digitizers were chosen (one a PDA,
and the other a table based digitizer), there was a statistically significant
difference between the two devices for 61 variables, including uptime,
distance, and event variables. Even though the signing area between the
two devices was constant, and the variables related to area measurement
such as measuring:
Area,
Distance (p-value = 0.000),
Net area (p-value = 0.000), and
Rubber area (p-value = 0.000),