Abstract:
Steganography is a means to hide the existence of information exchange. Using this technique the
sender embeds the secret information in some other media. This is done by replacing useless data
in ordinary computer files with some other invisible information. The hidden information could
be simple text, cipher text or even images. The media used as the embedding plane could be an
image, audio, video or a text files. Using steganography ensures that no one apart from the sender
and the receiver knows about the existence of the message.
In this thesis, a steganography method based on block differences is used. Each block consists of
three pixels. Two different differences are calculated for each block – between the first and the
second pixel and also between the second and the third pixel. The most recurring absolute block
difference in the whole image is used for embedding the secret message. To embed bit “1” or
“0”., the selected difference is either increased or left unchanged respectively. At the most a
single block can embed two bits “11” and only the middle pixel needs to be changed. Data
Compression is used to reduce the size of information so that the data hiding capacity of the
images could be increased.
The major advantage of using this technique is that the image quality is not degraded even if the
number of embedded characters is increased. The algorithm operates above 50 db in most of the
test cases. The average payload capacity is also considerably high
