Frequency scramble of speech and image by multidimensional digital signal processing

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This research studies multidimensional frequency scramble for secure communication of speech and images using multidimensional linear periodically shift-variant digital filters (LPSV filters). The notion of a generalized multidimensional transfer function is presented for LPSV filters. The frequency characteristic of the filters is discussed in terms of this transfer function. LPSV filters can serve as a frequency scrambler, because they can decompose the spectrum of an input signal into some spectral partitions and rearrange the spectrum. 2-D LPSV filters are designed based on the 1-D Parks-McClellan algorithm. The resultant LPSV filters divide the input spectrum into some components that are permuted and possibly inverted with keeping the symmetric of the spectrum. Application of the proposed scrabble method shows the effectiveness of frequency scramble for real images.