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Thursday, 22 February 2018

Extracting Spread-Spectrum Hidden Data from Digital Media (2013)

Extracting Spread-Spectrum Hidden Data 

from Digital Media (2013)


Extracting Spread-Spectrum Hidden
Data from Digital Media
              We consider the problem of extracting blindly data embedded over a wide band in a spectrum (transform) domain of a digital medium (image, audio, video). We develop a novel multicarrier/ signature iterative generalized least-squares (M-IGLS) core procedure to seek unknown data hidden in hosts via multicarrier spread-spectrum embedding. Neither the original host nor the embedding carriers are assumed available. Experimental studies on images show that the developed algorithm can achieve recovery probability of error close to what may be attained with
known embedding carriers and host autocorrelation matrix.

   In the existing system reversible data hiding technique the image is compressed and encrypted by using the encryption key and the data to hide is embedded in to the image by using the same encryption key. The user who knows the secret encryption key used can access the image and decrypt it after extracting or removing the data hidden in the image. After extracting the data hidden in the image then only can be the original image is retrieved.

             We propose the information hiding concept to reduce the risk of using cryptographic algorithms alone. Data hiding techniques embed information into another medium making it imperceptible to others, except for those that are meant to receive the hidden information and are aware of it presence. It focuses on methods of  hidden data in which cryptographic algorithms are combined with the information hiding techniques to increase the security of transmitted data.
          we focus our attention on the blind recovery of secret data hidden
in medium hosts via multi-carrier/signature direct-sequence spread-spectrum transform domain embedding.


              Steganography includes the concealment of information within computer files. In digital steganography, electronic communications may include steganographic coding inside of a transport layer, such as a document file, image file, program or protocol
              Digital steganography can hide confidential data (i.e. secret files) very securely by embedding them into some media data called "vessel data." The vessel data is also referred to as "carrier, cover, or dummy data". In Steganography images used for vessel data. The embedding operation in practice is to replace the "complex areas" on the bit planes of the vessel image with the confidential data. The most important aspect of Steganography is that the embedding capacity is very large. For a 'normal' image, roughly 50% of the data might be replaceable with secret data before image degradation becomes apparent.

Multi-Carrier  Spread Spectrum Embedding:
           The technique of spread spectrum may allow partly to fulfill the above requirements. Advantages of spread spectrum techniques are widely known: Immunity against multi-path distortion, no need for fiequency planning, high flexibility and variable data rate transmission. The capability of minimising multiple access interference in direct-sequence code- division-multiple-access system is given by the cross-correlation properties of spreading codes. In the case of multi-path propagation the capability of distinguishing one component fiom thers in the composite received signal is offered by the auto-correlation roperties of the spreading codes.  

Image encryption and watermarking:
The host image is an 8-bit or higher grey level image which must ideally be the same size as the plaintext image or else resized accordingly using the same proportions.
        Pre-conditioning the cipher and the convolution processes are undertaken using a Discrete Fourier Transform (DFT).
       The output will include negative floating point numbers upon taking the real component of a complex array. The array must be rectified by adding the largest negative value in the output array to the same array before normalization.
        For color host images, the binary cipher text can be inserted into one or all of the RGB components.
        The binary plaintext image should have homogeneous margins to minimize the effects of ringing due to ‘edge effects’ when processing the data using Fourier transform.

Image decryption and extraction:

(i) The correlation operation should be undertaken using a DFT.
(ii) For color images, the data is decomposed into each RGB component and each 1-bit layer is extracted and correlated with the appropriate cipher.
(iii) The output obtained in Step 3 has a low dynamic range and therefore requires to be quantized into an 8-bit image based on floating point numbers within the range max (array)-min (array).

System Configuration:-

H/W System Configuration:-

        Processor               -    Pentium –III

Speed                                -    1.1 Ghz
RAM                                 -    256  MB(min)
Hard Disk                          -   20 GB
Floppy Drive                     -    1.44 MB
Key Board                         -    Standard Windows Keyboard
Mouse                                -    Two or Three Button Mouse
Monitor                              -    SVGA

S/W System Configuration:-

Operating System            :Windows XP / 7
Front End                          : JAVA, RMI, SWING

                       We considered the problem of blindly extracting unknown
messages hidden in image hosts via multi-carrier/signature spread-spectrum embedding. Neither the original host nor the embedding carriers are assumed available. We developed a low complexity multi-carrier iterative generalized least-squares (M-IGLS) core algorithm. Experimental studies showed that M-IGLS can achieve probability of error rather close to what may be attained with known embedding signatures and known original host autocorrelation matrix and presents itself as an effective countermeasure to conventional SS data embedding/ hiding5.

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