Random encryption of speech signal

This paper presents an analog speech cryptosystem based on permutation and substitution of speech segments. Permutations processes and substitutions masks are variables which changed with changing the secret key. The main target of proposed system is to get non standard processes to decrease the complexity and diffusion of the system without affecting its security and depend on different security aspects like hidden block size and algorithm. We present a security analysis for the proposed cryptosystem against the brute-force and the statistical attacks from a strict cryptographic viewpoint. Experimental results verify and prove that the proposed speech cryptosystem is highly secure from the cryptographic viewpoint. It is shown that the permutations and substitutions induced by the new algorithm behave as typical random processes and can´t be predicted without the knowledge of the secret key. The results prove that this proposed cryptosystem has a very powerful diffusion mechanism to its secret key and increases robust to noise.