An appropriate system for securing real-time voice communication based on ADPCM coding and chaotic maps

Abstract

This paper presents a very simple and efficient encryption scheme based on controlled chaotic maps and ADPCM (Adaptive Differential Pulse Code Modulation) coding, in order to secure the real-time voice communication for operating at 16, 24, 32 or 40 kbps. This encryption algorithm adopts three main operations one to generate chaotic values using two chaotic logistic maps starting from independent initial conditions, the second to transform them into binary words using random encoding tables and the third to execute some basic operations and substitutions. It has important properties of randomness that can pass NIST batteries of tests. The evaluation and simulation analysis indicate that our proposal possesses an excellent statistical and cryptographic properties; it provides low correlation between adjacent samples in encryption speech, extremely sensitive encryption keys and has a large key space which is sufficient to protect against brute-force attack. As an illustrative example, an application on a commonly-encoder type used in communications, standard ITU-T G.726, is presented.