Polynomial-Based Image Sharing - Visual Cryptography and Secret Image Sharing - page 414

FIGURE 15.10
Partial area adjustments in the stego-images of "sailboat." (a) Lin-Tsai
scheme, (b) Yang et al.'s scheme, and (c) our scheme.

FIGURE 15.11
Replacement of "airplane" stego-image with "pepper." (a) original stego-
image of "Airplane", (b) replaced by "pepper" Lin-Tsai scheme, (c) replaced
by "pepper" in Yang et al.'s scheme, and (c) detected in our scheme.

Case I. Minor bit adjustments in the stego-images, with results compared in
Figure 15.9.

Case II. Partial area adjustment of a fake stego-image that can succeed the
fake scenarios in [4, 12], but this case is blocked in Wang et al.'s scheme, as
shown in Figure 15.10.

Case III. Replacement of a fake stego-image that was visually imperceptible
was detected in Wang et al.'s , shown in Figure 15.11. As observed in Figures
15.9{15.11, the three cases not detected by the schemes in [4, 12] were easily
made out when Wang et al.'s was applied. The probability of passing a fake
stego-image, in the scheme of Yang et al. [12], was ( 2 ) m 2

, where one bit

(4m) 2

4 = m 2 non-
overlapping blocks were set in the stego-image. On the other hand, in Wang
et al.'s, a block had an 8-pixel format, such that the probability of this block
succeeding was ( 2 ) 8 while the probability of a fake stego-image succeeding in

parity-check and hash were applied in a block (4-pixel) and