Modified scrambling based on permutation function matrix and 2D-DMWT with QPSK system

Abstract EN

Since an DWT- DMWT based speech scrambler retains aconsiderable residual intelligibility in the scrambled speech; thispaper proposes a new speech-scrambling technique to remove theresidual intelligibility from the scrambled speech.

The proposednew technique, based on the combination of an appropriate QPSK mapping method, can scramble speech withoutresidual intelligibility by permuting several frequencycomponents.

Without residual intelligibility in the scrambledspeech, the proposed QPSK speech scrambler is secure from frequency domain attacksby eavesdroppers.

In addition, the QPSK speech scrambler needs only two 2D(DWT-DMWT) operations insteadof the four required by the 1D(DWT-DMWT)based speech scrambler in systemstructure.

Simulation results are also presented to show theeffectiveness of this proposed technique.