Digital images are the most frequently used signals to convey information in the internet era. The security of these images is the primary concern in rapidly changing networked environments. In this research, we present a novel approach to secure images by integrating a scanning technique, the El-Gamal public key cryptosystem and chaotic systems. In brief, zigzag and spiral scanning are used first to construct a permuted image. Then, the El-Gamal encryption algorithm is exploited to encrypt the permuted image. Finally, Lorenz and Rössler chaotic sequences are utilized to scramble the pixel locations in the confusion and diffusion stages. This last step that mixes two stages can fortify the entire security performance and enlarge the key size. Exhaustive analysis has been carried out on the SIPI (signal and image processing institute) dataset to assess the efficiency and security of the proposed method. Numerical and visual results indicate the capability of the proposed image cryptosystem to protect images against several known attacks. In addition, the comparative analysis results indicate that the proposed approach outperforms the compared approaches in terms of the visual quality and security criteria.INDEX TERMS Image security, scanning, chaotic, Lorenz and Rössler sequences, El-Gamal algorithm.

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This article presents a performance comparison of two known public key cryptography techniques namely RSA (Rivest–Shamir–Adleman) and El-Gamal algorithms to encrypt/decrypt the speech signals during transferring over open networks. Specifically, this work is divided into two stages. The first stage is enciphering-deciphering the input speech file by employing the RSA method. The second stage is enciphering-deciphering the same input speech file by employing the El-Gamal method. Then, a comparative analysis is performed to test the performance of both cryptosystems using diverse experimental and statistical analyses for the ciphering and deciphering procedures like some known speech quality measures: histogram, spectrogram, correlation, differential, speed performance and noise effect analyses. The analyses outcomes reveal that the RSA and El-Gamal approaches are efficient and adequate for providing high degree of security, confidentiality and reliability. Additionally, the outcomes indicate that the RSA speech cryptosystem outperforms its counterpart the El-Gamal speech cryptosystem in most of ciphering/deciphering speech performance metrics.

One of the most important methods to protect and verify information that are exchanged over public communication channels in the existence of third party called antagonists is encryption. The stored or transmitted message is transformed in the encryption process to unreadable or gibberish form. The reverse process in which the intendent recipient can reveal the encrypted message content is called decryption. The encryption and decryption processes are achieved using secret keys that are exclusively exchanged between the sender and recipient. This method can be applied to any form of message such as audio, video, image or text data. The current work applies the well-known RSA algorithm for audio signal encryption and decryption. The performance of the presented algorithm has been tested via experimental implementation which show that the Cpestral Distance Measure (CD), Linear Predicative Code Measure (LPC) and Segmental Spectral Signal to Noise Ratio (SSSNR) reach to 6.8781, 4.9614 and -21.5563 dB respectively using Matlab simulations. The results on the presented technique validated that it is secure, reliable and efficient to be applied in secure audio communications as well as it performed high intelligibility of the recovered audio signal.