python - Steganographer File Handling Error for non plain-text files

Question

I\'ve built a Python Steganographer and am trying to add a GUI to it. After my previous question regarding reading all kinds of files in Python. Since, the steganographer ca

Answer 1

You can use and end-of-stream (EOS) marker when you are certain the marker sequence will not show up in your message stream. When you can't guarantee that, you have two options:

• create a more complicated EOS marker, comprised of many bytes. This can be quite the nuisance to prove the same problem won't arise as before, or
• Add a header at the beginning of your message, which encodes how many bits/bytes to read for the complete message extraction.

Generally, I'd use a header whenever I have information beforehand that I want to transmit and only rely on EOS markers when I don't know when my byte stream will terminate, e.g., on-the-fly compression.

For embedding, you should aim to:

• get your binary string
• measure its length
• convert that integer to a binary of fixed size, say, 32 bits
• attach that bitstring in front of your message bitstring
• embed all of that to your cover medium

And for extraction:

• extract the first 32 bits
• convert those to an integer to get your message bitstring length
• start from index 32 and extract the neccessary number of bits
• convert back to a bytestream and save to a file

As a bonus, you can add all sorts of information to your header, e.g., the name of the original file. As long as it's all encoded in a way you can extract it later. For example.

header = 4 bytes for the length of the message string +
         1 byte for the number of characters in the filename +
         that many bytes for the filename