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This paper presents a speech encryption scheme by performing a combination of modified chaotic maps inspired by classic logistic and cubic maps. The main idea was to enhance the performance of classical chaotic maps by extending the range of the chaotic parameter. The resulted combining map was applied to a speech encryption scheme by using the confusion and diffusion architecture. The evaluation results showed a good performance regarding the chaotic behaviors such as initial value, control parameter, Lyapunov exponent, and bifurcation diagram. Simulations and computer evaluations with security analysis showed that the proposed chaotic system exhibits excellent performance in speech encryption against various attacks. The results obtained demonstrated the efficiency of the proposed scheme compared to an existing valuable method for static and differential cryptographic attacks.

1 Abstract-In this paper, we propose an efficient image watermarking scheme based on combining Singular Value Decomposition (SVD) and Discrete Cosine Transform (DCT) transforms. The main idea consists of exploiting results obtained by the well-known Perona-Malik diffusion applied in image de-noising in watermarking domain by selecting significant blocks to embed a binary logo watermark. After applying the DCT on the selected blocks, the SVD is performed on each of these transformed blocks to modify a few numbers of its U matrix elements according to some defined conditions. Computer simulation and experimental results prove the efficiency of our proposed method against image processing attacks and outperform several previous schemes in terms of imperceptibility and robustness.Index Terms-Digital image watermarking; 2D discrete cosine transform; Singular value decomposition; Perona-Malik diffusion.

In this paper, the optical image encryption scheme based on the double random phase encoding system is modified by introducing a nonlinear digital image pre-encryption coupled with a real to complex conversion. It consists in performing the bit-wise XOR operation recursively between successive pixels of an input image together with chaotic scrambling in the spatial domain. The resulting real-valued pre-encrypted image is halved into two equal parts, one being considered as the real part and the other one as an imaginary part. The complex image thus constructed by concatenating the two previous parts, passes into the second stage of the double random phase encoding where it will be multiplied by a random phase mask and then transformed into a frequency domain by the two-dimensional Fourier transform or any of its derivatives to obtain the encrypted image. The advantage of halving is to save the same information and reduce the size of encrypted image to store or transmit a single complex image instead of double as in all existing based double random phase encoding methods. Results of computer simulations prove the effectiveness of the proposed method toward different attacks and confirm its security when compared to existing works, especially in terms of key sensitivity and histogram analysis.

In this paper, an improved Speckle Reducing Anisotropic Diffusion (SRAD), destined to remove multiplicative gamma noise applied to different images is proposed. The basic idea is to divide the image into several riddled areas and then calculate the Equivalent Number of Look (ENL) of each region. The largest value of the ENL is the best optimal homogeneous region of the image. This optimal choice allows us to solve the major problem of the SRAD algorithm articulated around a visual choice of the homogeneous region which is not satisfactory and causes non-uniformity in this area. To give more validity to the proposed method, several experimentations were conducted using different kinds of images and were approved by some quantitative metrics like PSNR, SNR, VSNR, and SSIM. The computer simulation results confirm the efficiency of the proposed method which outperformances the classical SRAD method.