Steganography with images and histogram checks

What is Steganography ?

Steganography is the hiding of a secret message within an ordinary message and the extraction of it at its destination. Here we have used an image to hide some message in side it. After encrypting the message we will try to analyze the histograms of the original image and the encrypted image to detect the differences of the images.

For more details : http://en.wikipedia.org/wiki/Steganography

Tools

Mozaiq - Online steganography tool

Mozaiq is an online steganography tool which provides a simple interface for hide plain text messages in a given image. Wikipedia states that terrorists has used this tool to send secret messages via public forum avatar images.

URL - http://mozaiq.org/encrypt

Mozaiq decryption tool

This decryption tool can be used to find the text message hidden in an image.

URL - http://mozaiq.org/decrypt

MatLab- To get histograms of the images and calculate the difference between the histograms of the images.

GIMP - To obtain visual representations of image histograms

Message

This is the message we encrypted using steganography for this experiment.

I am happy to join with you today in what will go down in history as the greatest demonstration for freedom in the history of our nation.

Five score years ago, a great American, in whose symbolic shadow we stand today, signed the Emancipation Proclamation. This momentous decree came as a great beacon light of hope to millions of Negro slaves who had been seared in the flames of withering injustice. It came as a joyous daybreak to end the long night of their captivity.

But one hundred years later, the Negro still is not free. One hundred years later, the life of the Negro is still sadly crippled by the manacles of segregation and the chains of discrimination. One hundred years later, the Negro lives on a lonely island of poverty in the midst of a vast ocean of material prosperity. One hundred years later, the Negro is still languished in the corners of American society and finds himself an exile in his own land. And so we've come here today to dramatize a shameful condition.

In a sense we've come to our nation's capital to cash a check. When the architects of our republic wrote the magnificent words of the Constitution and the Declaration of Independence, they were signing a promissory note to which every American was to fall heir. This note was a promise that all men, yes, black men as well as white men, would be guaranteed the "unalienable Rights" of "Life, Liberty and the pursuit of Happiness." It is obvious today that America has defaulted on this promissory note, insofar as her citizens of color are concerned. Instead of honoring this sacred obligation, America has given the Negro people a bad check, a check which has come back marked "insufficient funds."

But we refuse to believe that the bank of justice is bankrupt. We refuse to believe that there are insufficient funds in the great vaults of opportunity of this nation. And so, we've come to cash this check, a check that will give us upon demand the riches of freedom and the security of justice.

Side by side image view

         

Original Image Image with encrypted message        

Histograms of the Images

Histograms are obtained from both Matlab and GIMP.

           

Histogram of the Original Image

Histogram of the Encrypted message inside the image.

                                                  

Matlab code for obtaining two histograms and finding the difference between two histograms is given below. This is useful in measuring the quantitative statistical difference two images.

GIMP provides a detailed graphical interpretation of the histograms.This graphical representation provides a good sense of quantitative differences between two images.

Subtle differences in histogram peaks can be observed by carefully analyzing the two histograms.

We have used MatLab to draw the histograms of the given images. Here are the histograms created using matlab.

Here the histogram of the original image is one the left and the encrypted image’s histogram is on right.

We have coded a matlab function to calculate the differences between the histograms.  We have got an answer of 3.812e-0.005. This figure proves that there two images that we have used to calculate histograms are same to the human naked eye but they are actually two different images.