Grey Level Modification Steganography for Secret Communication

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Grey Level Modification Steganographyfor Secret
Communication

• V. POTDAR and E. CHANG
• M.Adnan KHAN
• Curtin University of Technology
• Perth Western Australia

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Motivation

• Security, Privacy, Anti-virus, Trusted computing,
  intrusion detection and information protection
• Critical components for industrial based IT
  solutions
• Third party vendors for protection
• Issues
• Trust of the third parties
• one industrial system, may have several trustees
• Solutions
• Use own security guard

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Proposed Solution

• Steganography for security and information
  protection
• an information hiding technique
• without a need for third party trustees
• Secret Communication

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Steganography

• Methods of transmitting secret messages
  through Carriers such as images, audio, video,
  text, or any other digitally represented code.
• The hidden message may be plaintext,
  ciphertext, or any-thing that can be represented
  as a bit stream.
• The problem
• Can be detected by careful statistical
  analysis

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Challenges

• the secrecy of the cover medium
• the robustness of the algorithm used
• To protect secrecy, we need to
• - discover new and better cover mediums or
• - design and develop robust algorithms
• The difficulties
• (a) information embedding capacity and
• (b) robustness of algorithms against detection

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Existing Research

• The existing research shows that the best way
  is to oversee the level of modification that is
  made to the cover media.
• IF modified too much the statistical changes are
  evident and such changes can indicate the use of
  steganography
• IF cannot be intelligently modified in a most
  secret way, it results in less embedding capacity

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Existing Research

• Existing Steganographic mediums and techniques
  suffer from a myriad of attacks on images, video
  and audio Johnson and Jajodia
• Great effort to defend the attacks by improving
  cover medium OR communication protocols.
• Defending techniques through covered medium
• Defending techniques through protocols

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Existing Research

• Defending techniques through covered medium
• Replacing Least Significant Bit Chen 2001, Lee
  et al. 2000
• Replacing Moderate Significant Bit Chan and
  Chang 2001
• Pixel Modification Techniques Zincheng et al.
  2003, Wu et al. 2003, Xinpeng and Shuozhong,
  2003, Soo-Chang and Jing-Ming, 2003 Zincheng et
  al. 2003 etc.
• Defending techniques through protocols
• the weaknesses of the TCP/IP Fisk et al. 2002
  
• email headers Bao et al. 2002
• the discrete cosine transform (DCT) and the
  discrete wavelet transform (DWT) Chang et al.
  2002, and Hsu et al. 1999.

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Existing Research

• this scheme is sensitive to a variety of image
  processing attacks like compression, cropping
• it degrades the quality of stego-image
• trade off high embedding rate
• vulnerable to steganalysis- based on histogram of
  pixel value differences

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A New Steganographic Approach

• embeds data or information within the spatial
  domain of the greyscale images by modifying the
  grey level values of the pixels.

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Preliminary Concepts

• A digital image f(x, y), When the values x, y and
  f are finite values then we call such an image a
  digital image.
• A image pixel is a definite location and
  amplitude that compose a image.
• Grey scale is Grey Level Values, a sequence of
  grey shades from black to white with intermediate
  shades of grey. It has a finite range 0, 2N-1,
• an 8 bit grey scale image range is from 0 to 255.
  

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Preliminary Concepts

• Grey Level Modification is defined as a technique
  in which the grey level values of the image
  pixels are modified in accordance with a
  mathematical function, to represent binary data.
  Each pixel has a distinct grey level value which
  can have an odd or even value. This odd or even
  value of the grey level is appropriately modified
  to represent binary data.

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Grey Level Modification Steganography (GLMS)

• GLMS is a technique in which the grey level
  values of the image pixels are modified in
  accordance with a mathematical function, to
  represent binary data.
• Each pixel has a distinct grey level value which
  can have an odd or even value. This odd or even
  value of the grey level is appropriately modified
  to represent binary data.
• GLM Steganography uses the concept of odd and
  even numbers to map data within an image. It is a
  one-to-one mapping between the binary data and
  the selected pixels in an image.

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Grey Level Modification Algorithm
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Formal Definition of GLM Algorithm
GLM Steganography modifies the value of l at a
coordinate (x0, y0) by n units based on an
arbitrary function g, which selects z number of
pixels from the matrix f(x, y) to map it to a bit
stream B of length .
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GLM Steganography Prototype Initial Screen
Implementation
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Java Code
The prototype is implemented using java. We
created 18 java classes. The screenshot shows the
ImageMain class and the adjoining classes
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Java Code
Binary1.java class. This class converts textual
data into binary format.
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This prototype has been tested on Jpeg, Gif and
BMP images to hide data
Image properties are shown here.
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The text to be hidden is entered in this text area
The text is first converted into binary format
which is then mapped with the image pixels.
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Grey Level Modification Steganography
The initial and final pixel values are shown
which are changed based on the bit that is mapped
with it
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The prototype has been tested on 1088 characters
or 7616 bits
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The pixel selection is based on a key. The
original and the modified values of the selected
pixels are shown in the text area
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Grey Level Modification Steganography
The modified image is saved as lena2.bmp
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Comparison of the histograms of the original and
modified image
There is very minute difference in the two
histograms which is not noticeable.
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Advantages

• It has low computational complexity
• high information hiding capacity
• The principle of the algorithm is to embed
  information by modifying the grey level values of
  the grey scale image pixels.
• We demonstrate this method by giving examples,
  implementation of prototype systems as proof of
  the concepts.

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Future Work

• Increase the embedding capacity.
• Prevent data loss from image modification like
  cropping, format change etc.

Thank you!