Complexity reduced multi-tier perceptual based partial encryption for secure speech communication

Present day secure speech communication mainly deals with providing maximum security at the cost of minimum complexity. While doing so, they are mainly looking forward to the speech coders for compressing the speech signal thus minimizing the complexity. In this paper an algorithm is proposed that aims at exploiting the basic characteristics of speech signal, while designing such system with reduced complexity. As observed from different speech signals, silent zones are present which comprises of about 30% to 40% of the whole speech. These zones do not bear any speech information. Processing these parts leads to significant increase in the computational complexity and also needs more frames to be transmitted. These can be avoided by removing such zones from the original speech signal. In case of secure speech communication, modern day encryption system does not provide the user, full flexibility in choosing the level of security. Those encryption algorithms mainly consist of single level of encryption. A scheme is proposed where up to three tiers of security levels can be achieved and the user is given the full flexibility in choosing the level of security one desires to impart to the speech communication system. Removal of the silent zones reduces the complexity which may circumvent the increasing computational complexity while implementing the multi-tier encryption algorithm.