Image Sharing with Steganography and Authentication - Visual Cryptography and Secret Image Sharing - page 446

FIGURE 16.27
The test images.
words, the size of the cover images used in the sharing algorithm should be no
larger than that of their secret images. However, the cover images produced
during previous research, which are based on a polynomial approach [9,15,28],
are much larger than their secret images. The cover-to-secret image size ratios
of the existing schemes and the proposed scheme are listed in Table 16.1 for
comparison. From Table 16.1, we can see the cover size/secret size of our
scheme is the smallest and the most satisfactory.
To evaluate the capacity to identify a region of the secret image that has
been tampered with, we compared the proposed scheme, Lin-Tsai's scheme,
Yang et al.'s scheme, and Chang et al.'s scheme using some manipulated stego-
images that satisfy the parity check policy (shown in Figure 16.30).
Both Figure 16.30 and Table 16.2 show the experimental results for the