Covert communications through mobile voice channels

The rapid development and growth of cellular mobile networks in recent years has made voice channels widely available almost everywhere. On the other hand, voice dedicated channels possess properties that make them ideal options for high priority real-time secure communications. Beside these realities, information embedding has gained remarkable attention in recent years due to its potential application in multimedia security. In this regard, this study aims to propose an efficient scheme for data hiding to show the feasibility of exploiting these channels for covert communications. To this end, the authors propose new suboptimal but practical schemes based on additive and multiplicative spread spectrum methods. The analytical evaluations of the proposed techniques along with simulation results show proper efficiency of these schemes. Moreover, it is shown that the proposed scheme based on the M-ary bi-orthogonal general maximum likelihood and M-ary bi-orthogonal generalised embedding of multiplicative watermarks techniques outperform the other proposed schemes in this study. Experimental evaluation confirms that the proposed data hiding scheme benefits from an acceptable level of imperceptibility. Finally, the authors propose a security block which considerably increases the robustness of proposed structures against histogram-based steganalysis.