Audio Steganography for Covert Data Transmission by Imperceptible Tone Insertion

This paper presents the technique of embedding data in an audio signal by inserting low power tones and its robustness to noise and cropping of embedded speech samples. Experiments on the embedding procedure applied to cover audio utterances from noise-free TIMIT database and a noisy database demonstrate the feasibility of the technique in terms of imperceptible embedding, high data rate and accurate data recovery. 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. In addition, results of two cases of attacks on the data-embedded stego audio, namely, additive noise and random cropping, show the technique is robust for covert communication and steganography.