F28HS2 Hardware Software Interface
This coursework involves building a simple steganography system in C. This system
will have a command-line interface (CLI) that allows its users to encode/hide a
message into an image, then reveal/decode the text from the image. Both encoding
and decoding will use secret keys. The application can be used by Alice and Bob who
shared a secret, say “2560867”. Alice can use the “encode” function to hide “Hello”
into an image using the secret “2560867”. Then, Alice can send the modified image
to Bob, who can use the “decode” function with the same key “2560867” to extract
the hidden message.
We hide text in images in this coursework by replacing the least significant bits in
some selected pixels of the image with bits from the characters we want to hide. The
pixels are chosen in a particular order that the receiver can reproduce. The text is
then retrieved by re-generating the pixel sequence, in the same original order, and
extracting message bits from them.
Least Significant Bit Technique.
Modifying the least significant bit (LSB) of each byte of a pixel causes minor
modifications that is not easy to spot by the human eye. For example, figure 1 shows
one pixel whose initial RGB values are: