Sharif Digital Repository

Nowadays, steganography is one of the secure communication methods. Exploitation of modern technologies has increased transmission bandwidth to a considerable scale. As a result of this, the multimedia signals such as Audio and Image have been used in communications widely. This application has led to the prevalent use of these signals as cover signals for carrying hidden messages. Given the proliferation of digital images, especially on the Internet, and given the large amount of redundant bits present in the digital representation of an image, images are the most popular cover objects for steganography. Simultaneously, steganalysis tries to defeat the very purpose of steganography by... 

Extracting the minutia of a fingerprint image and then hiding this information in the original image in order to increase the security has been explained and implemented in this thesis. One of the methods which can embed the predetermined digital data in the image is digital watermarking. In this thesis, the host image is a fingerprint image whose minutia has been embedded in that image. Embedding can be done in two spatial and frequency domains. In this thesis, embedding is implemented by combining two domains. Embedding in the frequency domain is applied to transforming coefficients directly from the image then by spatial method the information is embedded. Actually combining DWT and LSB... 

This thesis proposes new algorithms for digital watermarking that are based on Independent Component Analysis (ICA) technique. First, we will show that ICA allows the maximization of the information content and minimization of the induced distortion by decomposing the covertext (in this thesis the image) into statistically independent components. In fact, for a broad class of attacks and fixed capacity values, one can show that distortion is minimized when the message is embedded in statistically independent components. Information theoretical analysis also shows that the information hiding capacity of statistically independent components is maximal. Then we will propose a new wavelet... 

Steganography is the art 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. In this thesis, we focus on entropic issue of multimedia signal in the two branches of Information hiding namely Steganography and Watermarking. How to choose the block and noise estimation in the watermarking, and analysis of the singular values decomposition in steganography are examples of using entopic issue which we use in our thesis. The two new designs for video signals AVI are presented in Watermarking. For the both proposed method ,first AVI video signal will be divided... 

Up to now, compared with the comprehensive research for developing robust watermarking algorithms, no equal attention has been devoted to the proposition of benchmarks tailored to assess the watermark robustness. In addition, almost all the state of the art benchmarks only integrate a number of common image processing operations like geometrical transformations to remove watermarks. However, the quality of the processed image is often too degraded to permit further commercial exploitation. Moreover, to the best of our knowledge, the design of these tools does not take into account the statistical properties of the images and watermarks in the design of attacks. In spite of the significant... 

The goal of this thesis is using sparse decomposition to design secure steganography algorithms to insert secret data into the different cover signals. We propose data embedding in higher semantic levels of the cover signal to reach this goal. Sparse decomposition represents a signal as a linear combination of its structural elements. Data insertion into the sparse coefficients slightly changes the effect of structural elements in the signal representation. So, quality of the stego signal is preserved and such a steganography method leads to higher imperceptibility. In addition, data insertion into the higher semantic levels leads to the higher undetectability. Steganalyzers use statistical... 

Nowadays, with the increased penetration of wireless mobile networks (e.g. GSM, 3G, etc.), voice channels are widely available ubiquitously. This availability and wide coverage encourages utilization of such channels as a valuable available infrastructure for point to point secure data communication. This can be done either by using steganography and hiding the secure message in the voice passing through the channel or by ciphering and transmitting it through the voice channel as a speech-like signal. The proposed method for data communication or steganography through voice channels should be robust against lossy compression techniques applied by the vocoder block present in such channels....