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Title: Data Hiding using Steganography
Researcher: Shamim Ahmed Laskar
Guide(s): K. Hemachandran
University: Assam University
Completed Date: 
Abstract: With the spread of digital data across the world through the internet, the security of newlinethe data has raised a concern as data is the primary component of computer newlinecommunication. For providing better security of the digital data, different data newlinesecurity techniques are present with the objective of protecting the data. newlineSteganography is a data protection technique which has a wide range of applications newlinedue to its versatility and its potential to secure information. Among the file formats, newlineimages are the most popular cover-object for steganography because of the large newlineamount of redundant data present in its binary representation and its massive presence newlineon the internet. newlineThe primary work of this thesis focused on images as cover-medium and thus the newlinecontribution of this thesis is in the development of secure image based steganography. newlineFrom the study it is found that image based techniques basically works in spatial and newlinefrequency domain. Image based steganographic methods aims to make changes to the newlineimage statistics that does not cause degradation. This feature is not enough for newlinesecuring the data. Related to this, an effort has been made on expanding the existing newlinesteganographic algorithms by combining with cryptography. In the first case the newlinecryptography and DCT based steganography is combined to form a process that holds newlinethe features of steganographic and cryptography technique to increase the security of newlinethe secret data and to form a stego-image with minimal perceptual degradation. The newlinesecret message is first encrypted using substitution cipher method. Then the coverimage newlinewhich is to hold the secret data is preprocessed to reduce noise present in the newlinecover-image and increase the dependence between neighboring pixels, so that the newlineembedding process may better utilize the bits. The encrypted message is then newlineembedded in the DCT coefficients of high frequencies of the cover-image. newlineFurther the LSB based steganography is also combined with encryption technique to newlineenhance the embedding capacity of image steganography. The secret message is newlineencrypted two times, firstly using transposition cipher method and then with newlinesubstitution method before embedding into the cover-image. Then encrypted message newlineis embedded in an image by using least-significant-bit (LSB) based technique that newlineenables high capacity of data embedding. The main security lies in the encryption newlinemethod where the secret message to be embedded goes through double encryption newlineprocess which is controlled by two different keys. newlineThis thesis also introduces an approach of least significant bit (LSB) based newlinesteganography in digital images that can override some statistical and structural newlinemeasures of detecting steganography by spreading message bits randomly. One of the newlinemain characteristics of this steganographic technique is that the data are embedded newlineonly in the red plane of the cover-image s pixel which is determined by a newlinepseudorandom number generator (PRNG) initiated by a stego-key. Embedding only in newlinethe red plane makes small changes in the cover-image and such change is not visible newlineand detectable by the attacker. The usage of a stego-key is important, even when newlineknowing the image steganography algorithm the receiver will not be able to extract newlinethe secret data without the correct key which takes out the exact random locations of newlinethe secret bits. newlineIn order to examine the performance of the proposed techniques, some evaluation newlineschemes are conducted. The experiment has been performed on various images which newlineinclude both standard and natural images by embedding ASCII characters. Also the newlinecover-images used in the experimental evaluation consist of both gray-scale and color newlineimages of various dimensions. The secret messages that are embedded consist of text newlinecharacters of variable sizes. For evaluation of the steganographic techniques several newlinedependent variables are considered and all these variables are measured for the test newlineimages. The issues relating to the experimental approach are considered which is used newlinein the study to measure the impact of such embedding. Some experiments are used to newlinedemonstrate the validity of the proposed techniques and the comparative study of the newlineproposed methods with existing methods. It is also seen that the PSNR shows better newlineresults for all cases. Thus, from different test runs and the overall evaluation metrics newlinethe performance of the methods indicate good results. A comparative study of the newlineproposed steganographic methods is also conducted based on certain criteria. newline
Appears in Departments:Department of Computer Science

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