Abstract— In this paper, Steganography technique has been explained which deals with the art of
hiding data in files. Digital Steganography is implemented on an image and audio file to hide data
using Matlab tool. It has been explained that how data can be hidden in files like images, audio, video
or text without changing the quality or meaning of actual information. Further, Steganalysis is
discussed which is used to find the presence of steganographic objects inside the files. Some other
techniques such as Printed Steganography and Network Steganography are also explained.
Keywords— Steganography, Lossy Compression, Steganalysis, Stegdetect, Embedded Error.
I. INTRODUCTION
Steganography is the study and science of writing hidden messages in such a way that no one apart
Keywords— Steganography, Lossy Compression, Steganalysis, Stegdetect, Embedded Error.
I. INTRODUCTION
Steganography is the study and science of writing hidden messages in such a way that no one apart
from the sender and intended recipient suspects the existence of the message, a form of security
through obscurity. The word steganography is a Greek word means "concealed writing" from the
Greek words steganos meaning "covered or protected" and graphein meaning "to write" or Cover
Writing.
Steganography is often combined with cryptography such that, even if the message is discovered it
cannot be read. The major difference between Cryptography and Steganography lies with the fact that
when a message is encrypted, one already knows that the message exists and it is encrypted, whereas
with Steganography you might not even know (or observe) that there does exists a message too.
Steganography was also used by the terrorists responsible for the 9/11 attacks at the twin towers, this
was later figured out during the post attack investigation .
There are many types of techniques used in Steganography.
1. Physical steganography
2. Digital steganography
3. Network steganography
4. Printed steganography
II. PHYSICAL STEGANOGRAPHY
1. Physical steganography
2. Digital steganography
3. Network steganography
4. Printed steganography
II. PHYSICAL STEGANOGRAPHY
A. Hidden messages within wax tablets
In ancient Greece, people wrote messages on the wood and then covered it with wax, upon which an
innocent covering message was written.
B. Hidden messages on messenger's body
This technique was also used in ancient Greece. Herodotus tells the story of a message tattooed on a
slave's shaved head, hidden by the growth of his hair, and exposed by shaving his head again. The
message allegedly carried a warning to Greece about Persian invasion plans.
These two techniques are not prevalent now-a-days.
III. DIGITAL STEGANOGRAPHY
Modern steganography entered the world in 1985 with the advent of the personal computer being
III. DIGITAL STEGANOGRAPHY
Modern steganography entered the world in 1985 with the advent of the personal computer being
applied to classical steganography problems . Over 925 digital steganography applications have
been identified by the Steganography Analysis and Research Center . Digital steganography
techniques can be implemented on images, audio, video or text files as explained below.
A. Embedding messages within the lowest bits of noisy images.
A. Embedding messages within the lowest bits of noisy images.
Images are the most common ‘container’ for the hidden messages. A 24 bit image consists of 16
million possible colors. Each color is made up of three fundamental colors Red, Blue and Green. The
amount of Red, Blue and Green color is represented by 1 byte, which is 8 bits. A 24 bit image uses
bytes. If the least significant bits of the image are altered then also the image will have negligible
change.
Fig. 1 Steganography Using Images
Thus 1/8th of bits of the images are used to hide the secret data. Sometimes 3 Least important bits are
altered and changed by the data. A 24 bit image is very large and therefore rarely available on
internet and it also takes up multiple megabytes of data to send by email. So it is useful for other type
of images that are easily available on internet including bitmap and gifs.
JPEG image is not used with this technique because of ‘lossy compression’ used with JPEG images.
GIF uses loss less image compression technique so all the information of the picture is retained that’s
why GIF can be easily used to perform steganography. In JPEG picture compression, the data is
converted from the RGB values that describe individual pixels to the 'luminance' (brightness) and
'chrominance' (hue).The image is then divided in 8 by 8 pixel squares and each square run through a
'Discrete Cosine Transform' (DCT) whose data is quantified into DCT coefficients. The coefficients
are later compressed by a 'Variable Length Code'. All of this is done using special algorithms that
remove maximum possible data while maintaining the highest image quality. During the DCT step,
information in JPEG image is discarded. This is a major roadblock for steganography because data
cannot be placed into the image before JPEG encoding or it will be deleted by the DCT. Furthermore,
data cannot just be appended to the image after it is encoded because of the lack of security.
Fig. 2 Image before Steganography
Fig. 3 Image after Steganography
One can use any tool to perform steganography like Matlab or other image processing software.
Some software is available on internet to perform steganography using any of the technique. Any
type of data can be hidden using the same technique. Two or more files with different formats can be
hidden in the single image depending on the size of the data and image. Size of image may vary after
the steganography operation, due to the alteration in the LSB bits.
Total capacity of the image depends on the resolution of the image. Like an image having dimension 768x512 has 147,465 bytes of data hidden. To maximize the hiding capacity of the image, more than
just the LSB of an image must be used. However, simply using more bit-plane would not solve the
problem since this could cause visible marks or distortions to appear on the processed image. With
adaptive encoding each pixel uses different capacity depending on the tolerance of the pixel . A
pixel is said to be tolerant, if higher degree of changes to its value are possible.
Change cannot be identified by simple eye. If we go by pixel to pixel operation then only we can determine the change in to the images. Fig. 2 is the simple image on which steganography is to be performed. Fig. 3 is the image after the steganography operation.
The difference in the new image and the old image is called ‘Embedded Error’. Embedded Error depends on the source image on which the steganography has to be performed and the data which is
Change cannot be identified by simple eye. If we go by pixel to pixel operation then only we can determine the change in to the images. Fig. 2 is the simple image on which steganography is to be performed. Fig. 3 is the image after the steganography operation.
The difference in the new image and the old image is called ‘Embedded Error’. Embedded Error depends on the source image on which the steganography has to be performed and the data which is
to be hidden in the source image. If we increase the capacity using altering bit-planes, embedded error will increase which will cause visible mark or distortion on the image.
B. Steganography with Audio files
B. Steganography with Audio files
Audio files can also be used for steganography. Similar process is used to hide the data in the LSB’s
of audio data. By modifying the LSB’s of audio files minor change occur which cannot be
differentiated by the human ear. If we deal with every value of the audio file then only one can find
the change in them.
Echo data hiding is yet another method of hiding information inside an audio file. This method uses
Echo data hiding is yet another method of hiding information inside an audio file. This method uses
echoes in sound files in order to try and hide information. By simply adding extra sound to an echo
inside an audio file, information can be concealed. The thing that makes this method of concealing
information inside of audio files better than other methods is that it can actually improve the sound of
the audio inside an audio file.
Fig. 4 is the simple Audio file on which steganography is to be performed. Fig. 5 is the audio file after the steganography operation.
C. Steganography with Video files.
When information is hidden inside video, the program or person hiding the information will usually use the DCT (Discrete Cosine Transform) method. DCT works by slightly changing each of the images in the video, so it is not noticeable by the human eye. To be more precise about how DCT works, DCT alters values of certain parts of the images, it usually rounds them up. For example, if part of an image has a value of 6.667 it will round it up to 7. Steganography in videos is similar to that of steganography in images, apart from information is hidden in each frame of video.
Fig. 4 is the simple Audio file on which steganography is to be performed. Fig. 5 is the audio file after the steganography operation.
C. Steganography with Video files.
When information is hidden inside video, the program or person hiding the information will usually use the DCT (Discrete Cosine Transform) method. DCT works by slightly changing each of the images in the video, so it is not noticeable by the human eye. To be more precise about how DCT works, DCT alters values of certain parts of the images, it usually rounds them up. For example, if part of an image has a value of 6.667 it will round it up to 7. Steganography in videos is similar to that of steganography in images, apart from information is hidden in each frame of video.
D. Some Other Techniques.
The use of Steganography in documents works by simply adding white space and tabs to the ends of the lines of a document [6]. This type of Steganography is extremely effective, because the use white space and tabs is not visible to the human eye at all, at least in most text/document editors. White space and tabs occur naturally in documents, so there isn’t really any possible way using this method of steganography would cause someone to be suspicious. Hiding data in sudoku is the art of concealing data in an image using Sudoku which is used like a key to hide the data within an image. Steganography using sudoku puzzles has as many keys as there are possible solutions of a Sudoku puzzle, which is 6.7x1021. This is equivalent to around 70 bits, making it much stronger than the DES method which uses a 56 bit key.
E. Steganalysis
The art of detecting steganography in files is referred to as steganalysis. Steganalysis does not deal with trying to decrypt the hidden information inside of a file, just discovering it.
When we perform steganography the distortion in the image or audio files get distorted due to changing its bits. If any how we find that distortion using any technique then we will be able to find whether the data is hidden or not inside the file.
Viewing the file and comparing it to another copy of the file found on internet, we can determine the data. Steganography in audio files can be found by analysing the file bit by bit. To detect hidden information inside of a MP3 audio file you will need to find an audio file that uses the same compression (MP3) to compare them. DWT is also used to detect the information in the files. Just by comparing the DWT of two files one can easily determine the presence of steganographic objects.
When only a small amount of information is hidden inside a video it generally isn’t noticeable at all, however more is the information hidden the more noticeable it will become. Some softwares are also available to find the presence of hidden content in the files like XTEG and STEGDETECT. To find the steganographic content inside the document SNOW software can be used.
IV. NETWORK STEGANOGRAPHY
All information hiding techniques that may be used to exchange steganograms in telecommunication networks can be classified under the general term of network steganography. Contrary to the typical steganographic methods which utilize digital media (images, audio and video files) as a cover for hidden data, network steganography utilizes communication protocols' control elements and their basic intrinsic functionality.
V. PRINTED STEGANOGRAPHY
Digital Steganography output may be in the form of printed documents. Printing introduces much noise in the cipher text, generally rendering the message unrecoverable. There are techniques that address this limitation. One notable example is ASCII Art Steganography.
VI. CONCLUSION
It is concluded that Steganography can be a very useful technique to hide data in an image, audio, video or text file files, if used wisely without distorting the quality of files.
The use of Steganography in documents works by simply adding white space and tabs to the ends of the lines of a document [6]. This type of Steganography is extremely effective, because the use white space and tabs is not visible to the human eye at all, at least in most text/document editors. White space and tabs occur naturally in documents, so there isn’t really any possible way using this method of steganography would cause someone to be suspicious. Hiding data in sudoku is the art of concealing data in an image using Sudoku which is used like a key to hide the data within an image. Steganography using sudoku puzzles has as many keys as there are possible solutions of a Sudoku puzzle, which is 6.7x1021. This is equivalent to around 70 bits, making it much stronger than the DES method which uses a 56 bit key.
E. Steganalysis
The art of detecting steganography in files is referred to as steganalysis. Steganalysis does not deal with trying to decrypt the hidden information inside of a file, just discovering it.
When we perform steganography the distortion in the image or audio files get distorted due to changing its bits. If any how we find that distortion using any technique then we will be able to find whether the data is hidden or not inside the file.
Viewing the file and comparing it to another copy of the file found on internet, we can determine the data. Steganography in audio files can be found by analysing the file bit by bit. To detect hidden information inside of a MP3 audio file you will need to find an audio file that uses the same compression (MP3) to compare them. DWT is also used to detect the information in the files. Just by comparing the DWT of two files one can easily determine the presence of steganographic objects.
When only a small amount of information is hidden inside a video it generally isn’t noticeable at all, however more is the information hidden the more noticeable it will become. Some softwares are also available to find the presence of hidden content in the files like XTEG and STEGDETECT. To find the steganographic content inside the document SNOW software can be used.
IV. NETWORK STEGANOGRAPHY
All information hiding techniques that may be used to exchange steganograms in telecommunication networks can be classified under the general term of network steganography. Contrary to the typical steganographic methods which utilize digital media (images, audio and video files) as a cover for hidden data, network steganography utilizes communication protocols' control elements and their basic intrinsic functionality.
V. PRINTED STEGANOGRAPHY
Digital Steganography output may be in the form of printed documents. Printing introduces much noise in the cipher text, generally rendering the message unrecoverable. There are techniques that address this limitation. One notable example is ASCII Art Steganography.
VI. CONCLUSION
It is concluded that Steganography can be a very useful technique to hide data in an image, audio, video or text file files, if used wisely without distorting the quality of files.
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