Browsing by Author "Guerchi, Driss"

Now showing 1 - 9 of 9
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    An autoregressive time delay neural network for speech steganalysis
    (Institute of Electrical and Electronics Engineers Inc., 2012) Rekik, Siwar; Selouani, Sid-Ahmed; Guerchi, Driss; Hamam, Habib
    Hiding a secret message in speech signal, called steganography, is used to provide secure communication. The detection of hidden information in the transmitted message called steganalysis. The purpose of steganalysis is to identify the presence of embedded information, and does not actually attempt to extract or decode the hidden data. An automated method is required for detecting the existence of hidden message, since the huge amount of channeled information. However, the development and evaluation of steganalysis algorithms is a challenging task. In this paper we advocate a new steganalysis technique to classify a speech as having hidden information or not, using a powerful and sophisticated classifier called Autoregressive Time Delay Neural Network (AR-TDNN). The originality of this AR-TDNN is its quite ability to detect secret messages hidden with different steganographic algorithms, although the variation of detection rate depends on the particular hiding techniques and amount of hidden information. © 2012 IEEE.
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    Controlled distortion for high capacity data-in-speech spectrum steganography
    (Institute of Electrical and Electronics Engineers Inc., 2010) Djebbar, Fatiha; Hamam, Habib; Abed-Meraim, Karim; Guerchi, Driss
    Methods applied to ensure privacy of digital data became essential in many real life applications. Efficient secrecy can be achieved, at least in part, by implementing steganography techniques. In this paper, we present a technique that limits the impact of high data capacity embedding on the quality of stego wideband speech. Our method uses the energy of each frequency bin component to determine the maximum number of bits that can be confined without inducing any noticeable distortion on the cover speech. To guarantee good quality of stego speech, the embedding in the selected frequency components occurs below a well defined distortion level to limit the impact of the hiding on the stego-speech. The algorithm uses multiple parameters that can be adjusted by the sender to render the steganalysis work more challenging. The objective and subjective results show that this approach is robust to noise addition and maintains a very good quality of the cover signal while achieving high hiding capacity. © 2010 IEEE.
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    Dynamic energy based text-in-speech spectrum hiding using speech masking properties
    (Institute of Electrical and Electronics Engineers Inc., 2010) Djebbar, Fatiha; Abed-Meraim, Karim; Guerchi, Driss; Hamam, Habib
    In this paper we present a new method for text-in-speech Fast Fourier Transform (FFT) based steganography. Our method exploits high energetic magnitude frequency components of speech spectrum to hide the secret text. The energy level of each magnitude component is evaluated, and considered only if it is high enough to embed secret data. A frequency maskmg threshold is then calculated for each energetic frequency magnitude component to decide where to embed the secret text. As a result, the initial energy of the cover speech spectrum is slightly modified and the dIstortion error is always kept under the mask. The objective and subjective evaluations show that introducing the energy-based frequency masking 0l?ens new frontiers in text-in-speech steganography since hIgher bit rate text embedding was achieved while obtaining a stego-speech with unnoticeable distortion. © 2010 IEEE.
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    Encoding spectral parameters using cache codebook
    (Springer Nature Switzerland AG, 2012) Guerchi, Driss; Rekik, Siwar
    A new efficient approach to quantize the spectral line frequencies (LSF) in a coder is proposed. The use of the full search algorithm in the spectral parameters quantization causes high complexity and large hardware storage. Attempts to reduce the complexity have been performed by lowering the size of the LSF codebook. This option leads to a sub-optimal solution; the number of LSF vectors to be tested affects the performance of the speech coder. Cache codebook (CCB) technique enhances the search of the optimal quantized spectral information. In this technique the size of the main codebook is kept unchanged while the number of closest match searches is reduced. Unlike the classical quantizer design, the CCB method involves one main codebook embedding four disjoint sub-codebooks. The content of the CCB at any time is an exact reproduction of one of the four sub-codebooks. The search for the best match to an input vector is limited to the LSF vectors of the CCB. Some criteria are used to accept or reject this closest match. The CCB is updated whenever the decision is in favor of rejection. The cache codebook was successfully embedded in a CELP coder to enhance the quantization of the spectral information. The comparison simulation results show that the Codebook Caching approach yields to comparable objective and subjective performance to that of the optimal full-search technique when using the same training and testing database. © Springer-Verlag Berlin Heidelberg 2012.
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    Leaker identification in multicast communication
    (Springer Nature Switzerland AG, 2012) Mohamed, Emad Eldin; Guerchi, Driss
    Multicast is a communication mode in which data is exchanged among multiple end systems. An important concern in multicast communications is the protection of copyrights. While preventing copyright violations seems very difficult, tracing copyright violators (leaker identification) is more feasible and can be used as a deterrence alternative. In order to identify leakers in a multicast environment, every receiver should obtain a uniquely marked copy of the data. However, delivering unique copies from the sender to the receivers is inefficient. This paper investigates multicast leaker identification and introduces an efficient solution that is based on binary search tree. We introduce the notion of suspicious set that includes suspected end systems. When a leak is detected, all receivers are inserted in the suspicious set. Using a binary search, the suspicious set is refined successively until it includes only the leakers. An analytical study is conducted to evaluate the proposed solution. © Springer-Verlag Berlin Heidelberg 2012.
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    LPC-based narrowband speech steganography
    (Springer Nature Switzerland AG, 2012) Guerchi, Driss; Mohamed, Emad Eldin
    This paper proposes a new speech steganography system for secure sound massages sharing. This system exploits the advancements in speech processing to hide efficiently secret speech in narrowband cover speech. Linear predictive coding is used to represent the secret speech with reduced number of parameters. These parameters are embedded in selective perceptually-irrelevant frequency locations of the cover speech. Objective and subjective measures show that the resulting stego speech, which contains the secret message, is indistinguishable from the cover speech. © Springer-Verlag Berlin Heidelberg 2012.
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    On performing speech steganalysis using speech recognition and perceptual criteria
    (2010) Rekik, Siwar; Guerchi, Driss; Selouani, Sid-Ahmed; Hamam, Habib
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    Speech steganography using wavelet and Fourier transforms
    (Springer Nature Switzerland AG, 2012) Rekik, Siwar; Guerchi, Driss; Selouani, Sid-Ahmed; Hamam, Habib
    A new method to secure speech communication using the discrete wavelet transforms (DWT) and the fast Fourier transform is presented in this article. In the first phase of the hiding technique, we separate the speech high-frequency components from the low-frequency components using the DWT. In a second phase, we exploit the low-pass spectral proprieties of the speech spectrum to hide another secret speech signal in the low-amplitude high-frequency regions of the cover speech signal. The proposed method allows hiding a large amount of secret information while rendering the steganalysis more complex. Experimental results prove the efficiency of the proposed hiding technique since the stego signals are perceptually indistinguishable from the equivalent cover signal, while being able to recover the secret speech message with slight degradation in the quality. © 2012 Rekik et al.; licensee Springer.
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    Text hiding in high frequency components of speech spectrum
    (Institute of Electrical and Electronics Engineers Inc., 2010) Djebbar, Fatiha; Guerchi, Driss; Abed-Meraim, Karim; Hamam, Habib
    Boosted by recent advances in the information technology field, methods applied to ensure privacy of digital data became very important in many real life applications. Efficient secrecy can be achieved at least in part, by implementing steganograhy techniques. In this paper, we propose a new technique to hide text in wideband speech in noise free environment. We opted to work in the Fourier transform domain and hide the digital information within high frequency components. More precisely, our method exploits selected locations from the high-frequencies part of the cover speech to hide the secret text. We better preserve with high fidelity the spectrum shape of the speech carrier by employing an embedding rather than a replacement operation on the secret text. Our simulation results show that this approach maintains the robustness of the cover signal and achieves a higher hiding capacity. © 2010 IEEE.