Cryptography Reference
In-Depth Information
Fig. 8.9.
Gray scale representation.
Fig. 8.10.
LSB of Fig. 8.9 with Gray code.
intensity changes in the LSB plane for gray scale images. However, we can
detect unnatural patterns by looking the LSB plane. For example, Fig. 8.9
shows the stego-image with secret data embedded by BPCS with m =8
and α
TH
=46/112. The amount of the noisy region was about 31% of the
original image. All of the regions are substituted with noisy patterns and
the conjugation flags are embedded from the left upper block with raster
scanning without checking whether blocks are noise-like. Fig. 8.10 shows the
LSB plane of Fig. 8.9. We can easily see the unnatural pattern on upper
part by comparing the image with the gray scale representation (Fig. 8.9). In
general, the LSB plane for natural images looks like noisy patterns. Because we
know such the characteristic of the LSB plane, it is easy to detect unnatural
patterns from the stego-image, and it can be regarded as the signature of
BPCS.
