Cryptography Reference
In-Depth Information
Fig. 8.22.
An example of Link-to-Web extraction.
Table 8.8.
Size of the text files for JPEG embedding.
File name
1.highJPG.txt 1.lowJPG.txt 2.highJPG.txt 2.lowJPG.txt
Original size (KB)
149
25
50
7
Compressed size (KB)
44
9
16
3
Embedding
We did not use any Access Key in the experiment. The result of the JPEG
embedding is listed in Table 8.9. The file size of each JPEG output decreased
a little. The embedding capacity was around 10% of each output JPG file
(stego image) size. The reason why the JPG file decreases after embedding
is as follows. The JPEG embedding operation increases the number of 0
elements of the quantized DCT coe
cients and then the run-length-based
data compression process in JPEG coding eventually decreases the file size.
The embedding ratio was calculated as the ratio of the compressed text size vs
the JPEG stego image size. The difference pattern between before and after
embedding is shown in Fig. 8.23 (A) and (B). The largest differences in JPG-
