Speech Encryption with Fractional Watermark

Research on the feature of speech and image signals are carried out from two perspectives, the time domain and the frequency domain. The speech and image signals are a non-stationary signal, so FT is not used for the non-stationary characteristics of the signal. When short-term stable speech is obtained by windowing and framing the subsequent processing of the signal is completed by the Discrete Fourier Transform (DFT). The Fast Discrete Fourier Transform is a commonly used analysis method for speech and image signal processing in frequency domain. It has the problem of adjusting window size to a for desired resolution. But the Fractional Fourier Transform can have both time domain and frequency domain processing capabilities. This paper performs global processing speech encryption by combining speech with image of Fractional Fourier Transform. The speech signal is embedded watermark image that is processed by fractional transformation, and the embedded watermark has the effect of rotation and superposition, which improves the security of the speech. The paper results show that the proposed speech encryption method has a higher security level by Fractional Fourier Transform. The technology is easy to extend to practical applications.