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(7)
,
(8)
….
,
(9)
Fig. 2.
Sine transformation
3.4
Improve the Performance of Sine Transformation
Easy to see that, the minor transformation (7), (8), (9) in section 3.3 can increase error
rate of the system. We have to suppose another way to satisfy the disordered feature
of fuzzy vault. The new transformation is:
sin (x
i
+ y
i
) = c
i
(c
i
is chosen randomly between [-1, 1])
(10)
In addition, the sine function can map two points with large distance to new two
closed points. One example is shown in Fig. 3.
To avoid this phenomenon, the value of
is obtained by:
sin
, where
sin
2Π
,
(11)
It means that, we eliminate another solution:
sin
2Π
,
. Note that y
i
can be a negative number. The value of
lies between
2Π,2Π
. This new transformation is illustrated in Fig. 4. The output value y
i
will be
used as an input to fuzzy vault scheme presenting in next sections.
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