Cryptography Reference
In-Depth Information
0.06
after embedding
before embedding
0.05
0.04
0.03
0.02
0.01
0
0
0.2
0.4
0.6
0.8
1
complexity
Fig. 8.5.
Complexity histogram of 4th bitplane (α
TH
=0.41).
0.08
after embedding
before embedding
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0
0
0.2
0.4
0.6
0.8
1
complexity
Fig. 8.6.
Complexity histogram of 6th bitplane (α
TH
=0.41).
We embedded pseudo random data into the gray scale image called Peppers
(512512, 8 bit/pixel) using BPCS with α
TH
=0.41. Local regions on all
bit-planes having more than the threshold in complexity were substituted
with pseudo random data. Figs. 8.5 and 8.6 show complexity histograms of
the 4th and 6th bit-planes using BPCS with α
TH
=0.41. We can see an
unusual shape in the form of a valley near the threshold. The distribution of
the substituted pattern (complexities greater than the threshold) is a normal
distribution. In the middle bit-planes, noise-like patterns and non noise-like
patterns are mixed. In embedding in these planes, patterns that are above
the threshold change to the normal distribution and a discontinuity in the
complexity measure histogram around the threshold becomes noticeable.
8.3.2 Histogram Preserving Embedding
In BPCS, binary patterns for the replacement of noisy blocks are generated
from only secret data. In the proposed method, on the other hand, binary
patterns are generated both from secret data and the bits used to adjust the
complexity.
