Naglaa F. Soliman

Efficient implementation of chaotic image encryption in transform domains

Investigation of transform domain encryption.IWT encryption study.Study of chaotic Baker map permutation. The primary goal of this paper is security management in data image transmission and storage. Because of the increased use of images in industrial operations, it is necessary to protect the secret data of the image against unauthorized access. In this paper, we introduce a novel approach for image encryption based on employing a cyclic shift and the 2-D chaotic Baker map in different transform domains. The Integer Wavelet Transform (IWT), the Discrete Wavelet Transform (DWT), and the Discrete Cosine Transform (DCT) are exploited in the proposed encryption approach. The characteristics of the transform domains are studied and used to carry out the chaotic encryption. A comparison study between the transform-domain encryption approaches in the presence of attacks shows the superiority of encryption in the DWT domain.

Chaotic Interleaving for Robust Image Transmission with LDPC Coded OFDM

This paper presents a new technique for progressive image transmission over low-density parity-check coded orthogonal frequency division multiplexing (LDPC-OFDM) system. This technique adopts chaotic Baker map to improve the performance and reduce the peak-to-average power ratio (PAPR) of the OFDM signal. It helps improving the error resilient ability and also enhancing the efficiency of progressive image transmission over frequency selective fading channels. The proposed technique can effectively resist the fading impact of the frequency selective channels using simple frequency domain equalization. The proposed technique also utilizes the set partitioning in hierarchical trees as a source coding algorithm for the transmitted images. The distinctive feature of the proposed technique is that the transmitted data sequence has less data correlation, which leads to minimizing the PAPR. Simulation results show that the proposed technique improves the visual quality of the received images and reduces the PAPR of the OFDM signal as well.

Efficient Transmission of Encrypted Images with OFDM in the Presence of Carrier Frequency Offset

AbstractIn this paper, the impact of carrier frequency offset (CFO) and CFO compensation on the transmission of encrypted images with different orthogonal frequency division multiplexing (OFDM) versions is studied. The investigated OFDM versions are the fast Fourier transform OFDM, the discrete cosine transform OFDM, and the discrete wavelet transform OFDM. A comparison between four encryption algorithms with images transmitted through different OFDM versions is presented. These algorithms are data encryption standard, advanced encryption standard, RC6, and chaotic Baker map. This comparison aims to select the most appropriate version of OFDM, and the most suitable image encryption algorithm for efficient image transmission. In the simulation experiments, the peak signal-to-noise ratio at the receiver is used as an evaluation metric for the decrypted image quality.

Robust image transmission with OFDM over an AWGN channel

In this paper a new scheme is proposed for progressive image transmission over coded Orthogonal Frequency Division Multiplexing (OFDM) system with Low Density Parity Check Coding (LDPC). Trigonometric transforms are used in this scheme for improving the performance of the OFDM systems and reducing the Peak-to-Average Power Ratio (PAPR) of OFDM signal. It improves the error resilience ability and transmission efficiency for progressive image transmission over Additive White Gaussian Noise (AWGN) channel. The Set Partitioning In Hierarchical Trees (SPIHT) algorithm is used for source coding of the images to be transmitted. In the proposed scheme the transmit data sequence of the OFDM signal after Inverse Fast Fourier Transform (IFFT) is grouped into in-phase and in-quadrature components, then each component is transformed using either the Discrete Cosine Transform (DCT) or the Discrete Sine Transform (DST). The simulation results show that adding the DST to the system improves the visual quality of reconstructed images and reduces the PAPR of OFDM signal more than the DCT.

Peak power reduction of OFDM signals using trigonometric transforms

This paper presents a new technique, based on trigonometric transforms, to solve the peak to average power ratio (PAPR) problem associated with orthogonal frequency division multiplexing (OFDM) signals. In the proposed technique, both the in-phase and in-quadrature components of the OFDM signals after the inverse fast Fourier transform (IFFT) are transformed using either the discrete sine transform (DST) or the discrete cosine transform (DCT). It is known that both the DCT and the DST have an energy compaction property concentrating most of the signal energy in the first few samples after the application of the transform and leaving the rest of samples close to zero. This property can be exploited for PAPR reduction by interchanging the first half of samples of the in-phase component by the last half of samples of the in-quadrature component after applying the discrete transform on both of them, separately. The OFDM signal is transmitted in this format. By this process of replacement, it can be guaranteed that if either the in-phase or the in-quadrature component of the OFDM signal is large, the other will be small.

Peak power reduction of OFDM signals using chaotic baker maps

This paper presents a new approach for peak to average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) systems. This approach is based on the chaotic Baker map. It is known that OFDM transmitted signals are in complex format, having in-phase and in-quadrature components. If a chaotic randomization process is performed on each component, separately, prior to transmission, the likelihood that both the real and imaginary components of the transmitted signal at a certain time are of large amplitude gets lower. As a result, a reduction of the PAPR can be achieved. Simulation results show that the proposed PAPR reduction method achieves a performance improvement in the OFDM system.

Speech encryption using two dimensional chaotic maps

Speech encryption is used to convert clear speech into unintelligible signal in order to avoid eavesdropping for this purpose, cryptographic techniques and chaotic maps can be applicable. In this paper, a speech cryptosystem based on substitution and permutation is presented. The speech signal has been processed using different discrete transforms. Then the system has been developed using different chaotic maps like 2D Logistic map, Henon map, and Baker. Different objective quality measures for speech have been used to measure the quality of encrypted and decrypted speech signals.

Efficient Image Communication in PAPR Distortion Cases

AbstractIn this paper, a proposed method for Peak-to-Average Power Ratio (PAPR) reduction of Orthogonal Frequency Division Multiplexing (OFDM) signals based on discrete transforms is presented for robust image communication. One of the discrete transforms such as discrete wavelet transform, discrete cosine transform, or discrete sine transform is applied to modify the OFDM signal at the output of the inverse fast Fourier transform stage. We first present the proposed OFDM system model with trigonometric transforms for PAPR reduction. Trigonometric transforms improve the performance of the OFDM system, and reduce the PAPR of the OFDM signal. Then, this scheme has been utilized for progressive image transmission using low-density parity-check coded OFDM over frequency-selective fading channels. The set partitioning in hierarchical trees algorithm is used for source coding of the images to be transmitted. The proposed scheme effectively resists the fading impact of frequency-selective fading channels using simple frequency-domain equalization. Simulation experiments are performed for a variety of multipath fading channels. We also propose a chaotic interleaving scheme based on the 2-D chaotic Baker map for PAPR reduction of OFDM signals. The distinctive feature of this scheme is that the transmitted signal has less correlation between samples, and hence the PAPR is minimized.

An algorithm for pre-processing and segmentation of mammogram images

Breast cancer is one of the most common cancers worldwide. Breast cancer rates are high in low- and middle-income countries, where breast tumors are diagnosed late. Early detection of masses or abnormalities that indicate breast cancer is a very important step for treating breast cancer in its first stages. The early detection of breast cancer tumors depends on both the ability of radiologists to read mammogram images and the quality of these images. The target of this research is to present an algorithm, which assists the radiologists identifying breast tumors at their early stages. This paper studies an algorithm for the automatic removal of artifacts and noise that are present in mammogram images using morphological operations, and then it enhances contrast of mammogram images using the Band Limited Histogram Equalization (BLHE) method for easier detection of lesions or tumors. After preprocessing of mammogram images, this algorithm segments the images using Otsus N thresholding method to detect the region of interest in mammogram images.

Speech transmission with COFDM based on different discrete transforms

Recently, the multimedia and cellular technologies have spread dramatically. Therefore, the demand for digital information has increased. Speech compression is one of the most effective forms of communication. This paper presents three approaches for the transmission of compressed speech signals over convolutional Coded Orthogonal Frequency Division Multiplexing (COFDM) system with a chaotic interleavering technique. The speech signal has is compressed using the Set Partitioning In Hierarchical trees (SPIHT) algorithm, which is an improved version of EZW and which is characterized by a simple and effective method for further compression. For mitigation of the fading due to multipath wireless channels, this paper proposes a COFDM system based on fractional Fourier transform (FrFT), a COFDM system based on discrete Cosine transform (DCT), and a COFDM system based on discrete wavelet transform (DWT). The FrFT has the ability of solving the frequency offset problem, which causes the received frequency-domain sub-carriers to be shifted, and therefore, the orthogonality between subcarriers deteriorates even with equalization. The DCT has an advantage of increased computational speed as only real calculations are required. The DWT is spectrally efficient since it does not utilize cyclic prefix (CP). These systems have been designed under the assumption that corruptive background noises are absent. Therefore, denoising techniques, namely wavelet denoising and Wiener filtering methods are suggested at the receiver to achieve enhancement in the speech quality. The simulation experiments shows that the proposed COFDM–DWT with Wiener filtering at the receiver has a better trade-off between BER, spectral efficiency and signal distortion. Hence, the BER performance is improved with small bandwidth occupancy. Moreover, due to the denoising stage, the speech quality is improved to achieve good intelligibility.