by Mohd Shibli
Posted on 02 April 2017
Steganography is a technique by which we can hide information by embedding the data into other data objects, or simply we hide our data inside images, audio files etc.
The word Steganography combines the two greek words steganos meaning "covered" and graphien means "writing".
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Steganography was originated in greek and means "Covered Writing" , the technique can be seen in early centuries when passengers tattoo the message on their shaved heads and wait for the hairs to grow and then they travel to the destination and shave the head again to deliever the message.(i know that's cool haa! )
Steganography has become extermely popular in the past few years becuase of the rapid growth of the internet but nowadays people are using it mostly for malicious purposes, it has been used for terrorism , espionage,, fraud etc.
Steganography Vs. Cryptography
The only advantage of Steganography over Cryptography is Steganography does not draw the attention of anyone for example if i send a picture of a school to the school principal then it would look like a normal thing but the picture may consist a secret message inside it, but on the way to the principals office if anyone see it then mostly no one would be curious to see it as it is a normal picture as on the other side if i send an encrpted message written on a paper then it will draw a lot of attention and anyone who will see it will get suspicious regarding the message.
Steganography in digital images
Digital pictures can be used to hide messages on the internet and other communication medias, For example consider a 24-bit Bitmap which uses 8-bit each to represent three colors blue, green and red at each pixel, now if one pixel consist of the following color shade represented by 11111111 then we can change its least significant bit to 0(11111110), if we see the changes in the image then we will see no change as one color shade(for example royal blue) is changed into its next shade (for example dark blue) which our eyes will not be able to observe and hence we see no changes in the image similary if we change two more pixels in the image then we can encode a single ASCII character in it.
What is Steganalysis ?
Steganalysis is the process of detecting steganography, this is a new field and many opportunities are coming in the field of steganalysis as the popularity of steganography is increasing, there are two main types of Steganalysis
1) Visual Analysis
In this analysis the Steganalyist trys to decode the message only by inspecting the image with the naked eyes or with the assistance of a computer which can seprate the image into bits to simplify the job.
2) Statistical Analysis
It is more powerful and widely used as it reveals the smalled alterations in the images statistical behaviour, there are several tests which can be run on to the image to do the Statistical Analysis.
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