A novel approach based on stream cipher for selective speech encryption

This paper proposes a new approach to the encryption of speech intended to be transferred on an insecure channel. The proposed technique is based on stream encryption where the original speech is pre-processed in order to select the relevant data for encryption by removing the unvoiced parts of the signal. In addition to reducing the size of the speech signal, the selection process also reduces the encryption and decryption times. The selected data is encrypted using a pseudo-random generator to make the information unable to understand by an intruder. The used pseudo-random generator is based on two 256-bits shift registers, one is linear and the other non-linear. This generator allows encryption in higher dimensional space which expands the key space and, therefore, improves security against brute force attack. Various analyzis such as histograms, key space, key sensitivity, correlation, brute force attack, signal to noise (SNR) and peak signal to noise ratio (PSNR) have been performed. The analysis shows that the proposed scheme is computationally simple, efficient with superior performance compared to other systems presented in the literature.