Recognizing audio files containing hidden data, using FPGAs

Project outline: That might be strange if you hear that the music file which you enjoy listening to may contain esoteric data! As an example we believe that if someone substitutes every bit of his esoteric data with LSB bits of every byte in audio file, albeit the file has changed but human's ear cannot recognize the difference made by this substitution.
In this way it's possible to hide a secret data in a common music file and exchange it via an unsecure channel. Any auditor in the channel usually cannot even guess that there is a secret data in the file.

History of this strategy: previous similar works are mostly in the field of image processing. In fact this investigation is based on similar works with images.
At this point we hope that by plotting histogram of audio file we'll be able to distinguish modified file from an unmodified original one. We believe that there's a correlation between columns in histogram of original file but it's not applied to a modified one.
Our final goal: at last we hope that we can design an Fpga based system which can recognize audio files containing hidden data.

Project explanation:
At first we tried to use MATLAB and its signal processing tools to analyze modified and unmodified files. We should do a statistical research to finally find the main point of difference and apply it to our system.
The first step is finding bytes which has made the original audio file and plot it's histogram.
One way is to using "import data" in MATLAB. But we should notice that the default format of numbers in MATLAB is "double floating". And it imports audio file to a 1 column (if mono) or 2 columns (if stereo) matrix. The numbers are between 1 and -1 and in double format. But these kinds of numbers aren't suitable to plot a histogram. So we should invent another special way to create a vector of suitable numbers. Maybe that will be suitable to multiple all the numbers by 1000 and then round them simply by applying "data=round(data)" in MATLAB.Then we can plot histogram by this instruction:
hist(data)
In this point that became clear that we should have more specialized information about MATLAB and its "signal processing tools", so in next section we will make you more familiar with Signal processing in MATLAB.

Main primary points about MATLAB:
You can save all the variables currently in the workspace and load them the next time you need them by "save" and "load" commands.
Notice that "format" command only affects output display formats of numbers and does not affect how MATLAB computations are done.
You can change format of numbers using this command:
>> a=uint8(a);

To do list for next session:

• Continue studying MATLAB-jahad section2
  
• The file sent by Sahar which shows bytes of audio files
  

Wednesday 2008/31/7