Covert speech communication via cover speech by tone insertion

0-7803-7651-X/03/$17.00 © 2003 IEEE IEEEAC paper #1027, Updated November, 2002 Abstract --This paper presents the results of embedding a covert audio message in a cover audio signal for battlefield communication using steganography. Representing the covert message in a compressed or coded form, typically in the standard Global System for Mobile communication halfrate code (GSM 06.20), tones are added to the cover utterance in accordance with the coded bits. Based on the psychoacoustical masking property of the human auditory system, the added tones are set at very low power levels relative to the cover audio frames. The low power levels ensure that the tones are inaudible in the message-embedded stego signal. Besides imperceptibility in hearing, the spectrogram of the stego signal also conceals the existence of embedded information. Both of these features render the detection of embedding in the stego signal difficult to accomplish. Oblivious detection of the stego signal, instead of escrow detection, yields the embedded information accurately. By incorporating spread-spectrum techniques, the hidden message can be made further secure from unauthorized detection and modification. While the payload capacity of the proposed technique is low, the embedded information may be robust for retaining data under attack.