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High-grade narrowband speech security for high frequency (HF) can be achieved using low rate speech coders and encryption algorithms. This paper presents test results of HF channel and structure of used test system for digital plain and secure speech transmission using mixed excitation linear prediction (MELP) vocoder. Test results are: bit error percentage in the received MELP bitstream and spectrum characteristic and perceptual evaluation speech quality (PESQ) test for synthetic speech under a number of different test conditions. In this paper, we first analyze the transmission performance of the digital secure speech and then assess the speech quality performance according to HF channel distortions. To our knowledge, this is the first comprehensive performance analysis of the digital secure speech transmission over HF channel. Our results can be used to design technique of efficient secure communication for HF network. [ABSTRACT FROM AUTHOR]

When using a real random number generator (RNG) with only a hardware component, as required for statistical randomness, it is difficult to create an unbiased and stable random bit stream. Although the hardware generating processor generates an output bit stream quickly, if the software filter algorithm is not efficient, the RNG consumes a relatively large amount of time. This factor becomes the limiting condition when the RNG is applied. Accordingly, this paper proposes a model approach to ensure the model of software filtering in the RNG processor and the chaos function model in the crypto module. Therefore, in the embedded crypto processor, the mixed model guarantees randomness of the output stream, is generated from the combined chaos function with a tent map transformation and a hardware random number generation component in sensor crypto communication. [ABSTRACT FROM AUTHOR]

There are important performance issues in secure wireless networks, such as mobility, power, bandwidth, and bit error rate (BER), that must be considered when designing a communication resume protocol. The efficiency of a secure session resume for a fast resume of secure communication is a key point in secure connection development. In this paper, a fast secure communication resume protocol using the initialization vector (IV) count for a secure wireless network is presented and evaluated against the efficiency of conventional resume protocols. Our proposed secure session resume protocol is found to achieve better performance, in terms of transmission traffic, consumed time, and BER, than conventional resume protocols with the same security capabilities. [ABSTRACT FROM AUTHOR]

An interleaving algorithm is applied to reduce the loss of ciphered information when a cipher system transmits over a wireless security environment. As such, a new scheme for deciding the interleaving depth over a wireless mobile environment is described. Simulations confirm that the proposed dynamic allocation algorithm (DAA) with a non-fixed interleaving depth produced a better performance over a fading channel than a static allocation algorithm (SAA) with a fixed interleaving depth. [ABSTRACT FROM AUTHOR]

The analysis-by-synthesis/overlap-add (AbS/OLA) sinusoidal model has been applied to a broad range of speech and audio signal processing, such as coding, analysis and synthesis, fundamental frequency modification, time and frequency scale modification. This model uses an iterative analysis-by-synthesis procedure to estimate the sinusoidal parameters {amplitudes, frequencies, and phases}. However, one drawback of this model is that the analysis frame length is generally fixed in analyzing the signal. As a result, since each sinusoidal parameter has different frequencies, an analysis frame with fixed length cannot an optimal spectral resolution to each sinusoidal parameter. In this paper, in order to overcome this drawback and to estimate sinusoidal parameter more accurately, an AbS/OLA sinusoidal model using an elliptic filter is presented and evaluated against the performance of conventional AbS/OLA sinusoidal model. Our proposed AbS/OLA sinusoidal model is found to achieve better performance, in terms of spectral characteristics, phase characteristics, and the synthetic speech quality, than conventional model. [ABSTRACT FROM AUTHOR]