DESIGN AND IMPLEMENTATION OF INNOVATIVE STEGANOGRAPHIC 3 BIT PROCESS
Volumn 2

DESIGN AND IMPLEMENTATION OF INNOVATIVE STEGANOGRAPHIC 3 BIT PROCESS

Mr. Sanket Yeole1                                                                                                               

sanketyeole2011@rediffmail.com                                                         

Abha Gaikwad Patil College of Engineering

Mohgaon, Wardha road, Nagpur

Prof. Sagar Ghormade2

sagarghormade@gmail.com

Abha Gaikwad Patil College of Engineering

Mohgaon, Wardha road, Nagpur

Abstract

This paper brings the idea of novel approach to steganography where the data in one medium is hidden in another medium in such way that no one apart from sender and receiver suspect the existence of the message. In this we are using Least Significant Bit method to hide the content of the encoded audio message in the last two LSB bits of the pixels of the carrier color image. This paper overcome the drawback on previous method where the bits of the secrete audio data are hidden in the only last bit of the cover image thus offers more key based secure data transmission and reception with same cover medium. This paper brings the idea of novel approach to steganography where the data in one medium is hidden in an message in the last three LSB bits of the pixels of the carrier color image. This paper overcome the drawback on previous method where the bits of the secrete audio data are hidden in the only last two bits of the cover image thus offers more key based secure data transmission and reception with same cover medium. other medium in such way that no one except sender and receiver suspect the existence of the message. In this we are using Least Significant Bit method to hide the content of the encoded audio

Keywords:  steganography, RGB channels, LSB substitution, bit array conversion  

1. Introduction

Major requirement of today’s computer communication is to prevent the data to be disclosed to the illegal user. Various technique of such data hiding are steganography, cryptography, watermarking etc. Apart from these Steganography is the practice of hiding private or sensitive information within something that appears to be nothing. Both techniques are use to protect important information. The difference between the two is that Steganography involves hiding information so it appears that no information is hidden at all. Steganography in the modern day sense of the world usually refers to information or a file that has been concealed inside a digital picture, video or audio file. What Steganography essentially does is exploit human perception, human senses are not trained to look for files that have information hidden inside them, although there are programs available that can do what is called steganalysis. Data hiding, or steganography, is a challenging area of research which has attracted much attention for centuries. As an active area of research, new techniques are constantly emerging using LSB algorithm. In contrast to the active research focusing on image or video schemes , there is little research on data hiding in audio schemes. However, effective audio data hiding in an color image can create robust and imperceptible data thus allowing property rights protection or secret data exchange.

Basic terminologies associated with the steganography are summarized below which help in the further approach.

Payload: The information which is to be concealed, here we use audio as payload

Carrier File: The media where payload has to be Hidden which is color image we use here.

Stego-medium: The medium in which the information is hidden.

Redundant Bits: Pieces of information inside a file which can be overwritten or altered without damaging  the file.

Steganalysis: The process of detecting hidden information inside the file. The advance  steganography  process can be understood properly by following rule: Coverimage + Audiomessage + Stegokey =  stego image

2. RGB color channels and LSB substitution method

An image can be represented by a collection of color pixels. The individual pixels are represented by their optical characteristics like “brightness”, “intensity””contrast”,etc. Each of these characteristics can be digitally expressed in terms of 1’s and 0’s. basic There are three color channels that present different forms for storing images. A color space is a method by which it is possible to specify, create and visualize color. The most common color space among all is RGB (Red, Green, and Blue). The RGB color model is additive in the sense that the three light beams are added together, and their light spectra add, wavelength for wavelength, to make the final color’s spectrum. Each pixel in a 24-bit bitmap image in this space is described by 3 sets of 8 bits (3 bytes), that each set contains the intensity value of individual red, green and blue. Combination of these values forms the characteristics of the pixel. The RGB color model already had a solid theory behind it, based in human perception of colors. One simple method is LSB, or Least Significant Bit Steganography. An image is nothing more than strings and strings of bytes, each byte representing a different color. The last few bits in a color byte, however, do not hold as much significance as the first few. This is to say that two bytes that only differ in the last few bits can represent two colors that are virtually indistinguishable to the human eye.

For example, 00100110 and 00100111 can be two different shades of Red, but since it is only the last bit

that differs between the two, it is impossible to see the color difference. LSB Steganography, then, alters

these last bits by hiding a message within them. To hide a secret message inside an image, a proper cover

image is needed. Because this method uses bits of each pixel in the image, it is necessary to use a  lossless compression format, otherwise the hidden information will get lost in the transformations of a lossy compression algorithm. When using a 24-bit color image, a bit of each of the red, green and blue color components can be used, so a total of 6 bits can

be stored in each pixel. For example, the following grid can be considered as 3 pixels of a 24-bit color  image, using 9 bytes of memory:

(100110011  11001110  101110010)

( 011010011 10101010  101111010)

(11001000   00100111   101000100)

When the character B, which binary value equals 10000010, is inserted, the following grid results

(00100111 11101000 11001000)

(00100110 11001000 11101000)

(11001000 00100111 11101000)

In this case, only three bits needed to be changed to insert the character successfully. The result changes that are made to the least significant bits are too small

to be recognized by the human visual system (HVS), so the message is effectively hidden. As one can see,

the least significant bit of the third color is remained without any changes. It can be used for checking the correctness of 8 bits which are embedded in these 3 pixels. In other words, it could be used as “parity bit”.

3. Proposed methodology of LSB

The conventional method says, one LSB can be replaced with the data bit. Instead of hiding a single bit in each byte, two bits of data can be hidden in a single byte as it can cause no change in the image as per the human visual system. As there are 8 bits in a byte, first and the second and third bits can be hidden in Red values and next three bits in the green value and next three in the blue value byte. For example, consider the 24 bit pixel value-

11001000   00100111 101000100

Consider the data byte- 111 010 110

Data can be hidden in the following way-

00100111 010010101 1010110

The main advantage of this technique is the increase in the amount of space for hiding the data. Thus 1 byte of audio data can be hidden in the one pixel of the cover image.

3.1 Bit array conversion

The cover image to hide the data is the 8 bit image is  converted into bit array format as well as the audio file acting as secrete data is also converted into bit format only then the hiding can be achieved.

Bit array 1 : Header

Bit array 2 : size of audio file

Bit array 3 : contents of audio file

3.2 Hiding an audio message

When an audio file divided into different field like header, size of data, and the content of audio message, bits per sample format etc each of these field is converted into bit array to hide in the digital color image. The mostly used audio files are WAVE file which have fixed byte header and all  the contents are arranged in sequence but it require large memory so that less data limit this file application. So in  this approach we use MPEG layer 3 (mp3)file also  where the data is appear in compressed form so that more content  can be obtained in same memory and then  hidden in the cover medium i.e. color image.

The relation between the size of the audio file in bytes (A) and that of  cover image in the pixel (P) is given by,   8*A=3*W*H,

Where, W and H are the width and height of the cover image

.Therefore maximum size of audio file given by,

A=3*w*H/8

Lets consider MP3 having 56 bytes dedicated for header then remaining bytes reserved for the audio content. Then,

A=56+M,

Where, M- actual size of the message in bytes.

Thus,

M= [3*w*H/8]-56.

4. Block Processing

Encoder block used for hiding the audio message in the image. This audio message is first sampled and then converted into binary format and then encoded with color image using LSB technique as discussed above. Figure 2 use for extraction of the original audio content at the receiver. Firstly it obtained in binary form and then converted into audio form using appropriate MATLAB tools. Stego key is used in both transmitter and receiver block for secure communication.

Figure 1. Hiding the  audio message
Figure 2. Recovering the audio message

5. Implementation and Output

Using image processing toolbox above proposed work has been implemented. We obtained the snapshot of the result which show the color image converted into the binary form shown in fig 3. A group of images shown in fig 4 and fig 5, before and after hiding the content of audio information using method mentioned previously. The last three least significant bit are replaced by the mp3 audio message content using encryption technique. The mp3 or wave audio content are recovered using decryption technique. The changes in the cover image in which the audio is hidden are so small that cannot be observed by the human perception. Thus, stego image looks like the cover image and the recovered audio message will also appears identical to the original data that was sent.

Figure 3. Snapshot of color image in bit array form
Figure 4. Before and after steganography(1.50MB mp3 in 1600*900) JPEG  image
Figure 5.Before and after Steganography(810KB wave file in 553*428 JPEG image.

6. Conclusion

This technique provide greater amount of flexibility to the user since it allow the hide the audio content in the last three bit of each byte. Therefore it avoids the major limitation of conventional method so more data can be hidden within same medium.. More than three bit for data hiding gives the blurred stego image which can easily suspected by intruders. The future work could be extending to embed the audio message in the video file. The secrete audio channel can also be hide within the broadcasting medium using this technique.

7. References

  1. V. J. Rehna, Member, IACSIT and M. K. Jeya Kumar ,“A Strong Encryption Method of Sound Steganography by Encoding an Image to Audio”, International Journal of Information and Electronics Engineering, Vol. 2, No. 3, May 2012.
  2. M.I.Khalil, “Image Steganography, Hiding short audio messages in digital images”, JCS&T Vol 11 No.2.
  3. Jeremiah J. Harmsen,” Capacity of Steganographic Channels” IEEE Transactions On Information Theory, Vol. 55, No. 4, April 2009.
  4. Nicholas Hopper, Luis von Ahn, and John Langford” Provably Secure Steganography” IEEE Transactions On Computers, Vol. 58, No. 5, May 2009.
  5. Mauro Barni” Watermark Embedding: Hiding a Signal within a Cover Image”, IEEE Communications Magazine August 2001.

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