TDSi DIGIgarde PLUS - Threshold; Privilege Levels; Table 4 Suggested Threshold Settings

Introduction
DIGIgarde PLUS User Guide
Copyright © 2012 TDSi Last Change
Page 6 13 May, 2016
1.3.3
1.3.31.3.3
1.3.3 Threshold
ThresholdThreshold
Threshold
The quality of scanned fingerprints can be variable. This opens up the possibility of
two types of verification failure:
Valid users are rejected. This is called False Rejection. The False Rejection
Rate (FRR) is the probability that DIGIgarde PLUS will fail to identify an enrolled
user, or verify their legitimate identity.
An imposter is mistakenly accepted because of the similarity of their fingerprint
to that of a registered user. This is termed False Acceptance. The False
Acceptance Rate (FAR) is the probability that DIGIgarde PLUS will incorrectly
verify an individual or will fail to reject an impostor.
To minimize these effects, DIGIgarde PLUS uses a Threshold value to establish a
balance between False Acceptance and False Rejection. A high threshold value
reduces the chances of false acceptance but increase the probability of false
rejection. The default Threshold value is 35 for 1:N matching and 15 for 1:1
matching. Clearly, the chance of a false acceptance is much less when a user ID is
required since the DIGIgarde PLUS is only comparing the scanned fingerprint with
one template.
The threshold can be set for all users. Raising the threshold increases security,
while lowering it increases pass rate.
For a user whose fingerprint verification is difficult, you can either reduce the
threshold or adopt ID & Fingerprint verification (1:1 verification) – see page 45.
Table 4 Suggested Threshold Settings
FRR FAR 1:N 1:1
High Low 45 25
Middle Middle 35 15
Low High 25 10
1.3.4
1.3.41.3.4
1.3.4 User ID
User ID User ID
User ID n
nn
numbers
umbersumbers
umbers
During enrolment, DIGIgarde PLUS assigns a User ID Number to each user. This
ID can be used to call up the fingerprint template (1:1 verification) and/or password
each time that verification is requested.
A user can enter their ID number using the keypad or it can be called up from an
RF Card or Mifare Card.
1.3.5
1.3.51.3.5
1.3.5 Privil
PrivilPrivil
Privile
ee
ege
ge ge
ge l
ll
levels
evelsevels
evels
DIGIgarde PLUS recognizes four Privilege levels:
Users
People whose identity must be verified to gain access to a facility or to have
their attendance recorded.
Enrollers
DIGIgarde PLUS users who are authorized to enrol or delete users in the
system.
Managers
Additional powers except set advanced options and enrol manager or above
privilege users.