Information Technology Reference
In-Depth Information
12
Upper bound
LSB embedding
Ternary embedding
10
8
6
4
2
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Embedding rate
Figure 10.2
Theoretically achievable bound on embedding efficiency.
10.3 Conventional
±
1 Steganography
Traditional embedding schemes for implementing ±1 steganography are
introduced here to demonstrate the performance improvement offered by the
proposed scheme. The LSB embedding is a simple algorithm for ±1 steganog-
raphy, in which secret messages are conveyed in the LSB of the color values of
selected pixels. Then, ternary embedding is applied to improve embedding
efficiency. This section also presents performance analyses of conventional
embedding methods for comparison with the proposed scheme.
10.3.1 Least-Significant-Bits embedding
Suppose that a pixel's grayscale value
c
i
is represented as a binary vector
b
7
, …,
b
1
,
b
0
so that
7
∑
2
0
c
=
b
×
.
h
i
h
h
=
Secret messages are embedded only in the least significant bits (LSBs) of
this binary representation. To implement ±1 steganography, we assume that
each message bit
m
i
is embedded in the 1 LSB of each pixel so that
h
=+ ×
=
∑
2
1
sm
b
,
h
i
i
h
h
