| Covert communication of secret information based on speech has been a hotspot in secure communication and military communication. Secret data transmitted in open networks in war has been one of the advanced subjects studied in information warfare. Using data hiding techniques, secret data was embedded in imperceptible multimedia data which did not raise any suspicion by our ears and eyes and was not easily to be detected. Secret data was secretly transmitted in open channels, and so covert communication adds a safeguard compared to traditional encryption techniques. Speech signal was widely used in communication, so research on data covert communication based on speech was very important in information security, secure communication etc. This dissertation focused on the development of methods of covert communication especially covert communication based on speech and its relative key techniques.A high data embedding efficient secret Chinese characters covert communication method based on RPE-LTP speech of wireless network was proposed. Secret Chinese characters were embedded in some imperceptible parts of the host data and secretly transmitted in open channels. Using the method, 300 bits/s of data were embedded in the host speech.In order to reach the demands of large capacity and high rates of streaming media data embedding, a new scheme capable of hiding a 2.4kb/s low-bit-rate mix-excitation linear prediction (MELP) speech into another RPE-LTP speech was proposed. The MELP speech can be secretly transmitted in open channels. It was difficult to detect the difference between the host RPE-LTP speech embedded a MELP speech and the original host RPE-LTP speech.Now, most data embedding and extracting algorithms have higher time complexity and could not process signal on line. In order to reach the demands of real-time, high speed and large capacity data covert communication, data embedding and extracting algorithms must be implemented by hardware generally. The hardware...
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