Cryptography Reference
In-Depth Information
If both k
c
and k
s
are the the target complexity, we choose one of them
randomly. If k
c
and k
s
do not satisfy the above conditions, then the value
of e is changed by
1
2m(m−1)
,
e←e +
(8.11)
and the above conditions are re-checked. The target complexity is denoted
by C
t
in the following.
The complexity of P
i
is adjusted by the following steps using the target
complexity and h
EMB
and h
ORG
.InPAConP
i
, there are pixels having the
property that the complexity of P
i
becomes larger by reversing its value. We
denote the set of pixels having the property as B
+
. There are also pixels
having the property that the complexity of P
i
becomes smaller by reversing
its value. We denote the set of pixels having the property as B
−
.
b-1) Go to the step b-2 if P
i
satisfies the following condition,
α(P
i
) <c.
(8.12)
Go to the step b-3 if P
i
satisfies the following condition,
α(P
i
) >c.
(8.13)
Go to the step b-4 if the above conditions are not satisfied, this means
α(P
i
)=C
t
.
b-2) Choose a pixel from B
+
, reverse the its value and remove it from B
+
.
Choose a pixel randomly if there are pixels having the same property. This
step is repeated until α(P
i
) is equal to C
t
or greater, or B
+
is empty. In
order for P
i
to satisfy noisy pattern, the pixel value of the last pixel that
has been reversed is reversed if the following condition is satisfied,
α(P
i
) > 0.5+δ.
(8.14)
Go to b-4 if this step is finished.
b-3) Choose a pixel from B
−
, reverse the its value and remove it from B
−
.
Choose a pixel randomly if there are pixels having the same property. This
step is repeated until α(P
i
) is equal to C
t
or smaller, or B
−
is empty. In
oder for P
i
to satisfy noisy pattern, the pixel value of the last pixel that
has been reversed is reversed if the following condition is satisfied,
α(P
i
) < 0.5−δ.
(8.15)
Go to b-4 if this step is finished.
b-4) h
EMB
(c) is changed by the following equation,
h
EMB
(α(P
i
))←h
EMB
(α(P
i
)) + 1.
(8.16)
