Cryptography Reference
In-Depth Information
hide a secret image. Let T =T
1
,T
2
,,T
2
k
be the set of 2
k
sub-regions,
where T
i
is the i-th sub-region. The total number of sub-regions in the gray-
scale image is 2
k
which means we have 2
k
secret images in the gray-scale
image.
In the second step, the gray-scale image is represented by eight bit planes.
Let P =P
1
,P
2
,,P
8
be a set of eight bit planes of the image. Here
P
j
=T
1
,T
2
,,T
2
k
is the j-th plane, which consists of several sub-regions.
(a) encryption process
(b) decryption process
Fig. 4.5.
Diagram of the proposed scheme.
The third step is to generate shadows for each binary plane P
j
.Theshadow
generation process for P
j
is shown in Fig. 4.6. The scheme splits each bit of
the sub-region into several blocks by using Naor and Shamirs encryption
function.
The encryption function maps each bit of T
i
into a block of size 22from
C
0
or C
1
to different shadows. If the color of the input bit is white, then the
blocks are randomly chosen from C
0
. Otherwise, the color of the input bit is
