Robust Covert Communication over a Public Audio Channel Using Spread Spectrum

We present a set of watermarking techniques for effective covert communication over an audio signal carrier. Watermark robustness is enabled using: (i) redundant spread-spectrum for prevention against desynchronization attacks and (ii) psycho-acoustic frequency masking (PAFM). We show that PAFM impacts the balance of "ones" and "zeros" in the part of the spread-spectrum sequence used for watermark detection and propose a modified covariance test to compensate for that anomaly. The covert message is combined with the spread-spectrum sequence and additionally permuted in time to improve correlation convergence as well as the security of individual message bits. We have incorporated these techniques into a system capable of reliably detecting watermarks in audio that has been modified using a composition of attacks that degrade the original audio characteristics well beyond the limit of acceptable quality. Such attacks include: fluctuating scaling in time and frequency, editing, recompression, noise addition, resampling, normalization, and filtering.

[1]  Ahmed H. Tewfik,et al.  Robust audio watermarking using perceptual masking , 1998, Signal Process..

[2]  Ingemar J. Cox,et al.  A Secure, Robust Watermark for Multimedia , 1996, Information Hiding.

[3]  Markus G. Kuhn,et al.  Attacks on Copyright Marking Systems , 1998, Information Hiding.

[4]  Henrique S. Malvar.  A modulated complex lapped transform and its applications to audio processing , 1999, 1999 IEEE International Conference on Acoustics, Speech, and Signal Processing. Proceedings. ICASSP99 (Cat. No.99CH36258).

[5]  Edward J. Delp,et al.  Communications approach to image steganography , 2002, IS&T/SPIE Electronic Imaging.

[6]  Jürgen Herre,et al.  Digital Watermarking and Its Influence on Audio Quality , 1998 .

[7]  Harry L. Van Trees,et al.  Detection, Estimation, and Modulation Theory, Part I , 1968 .

[8]  Bernd Girod,et al.  Spread spectrum watermarking: malicious attacks and counterattacks , 1999, Electronic Imaging.

[9]  Ross J. Anderson,et al.  On the limits of steganography , 1998, IEEE J. Sel. Areas Commun..

[10]  Henrique S. Malvar,et al.  Speech dereverberation via maximum-kurtosis subband adaptive filtering , 2001, 2001 IEEE International Conference on Acoustics, Speech, and Signal Processing. Proceedings (Cat. No.01CH37221).

[11]  Mark Kahrs,et al.  Applications of digital signal processing to audio and acoustics , 1998 .

[12]  Henrique S. Malvar.  Auditory masking in audio compression , 2001 .

[13]  Walter Bender,et al.  Echo Hiding , 1996, Information Hiding.

[14]  Ioannis Pitas,et al.  Robust audio watermarking in the time domain , 1998, 9th European Signal Processing Conference (EUSIPCO 1998).

[15]  Henrique S. Malvar.  Enhancing the performance of subband audio coders for speech signals , 1998, ISCAS '98. Proceedings of the 1998 IEEE International Symposium on Circuits and Systems (Cat. No.98CH36187).

[16]  Gregory W. Wornell,et al.  Digital watermarking and information embedding using dither modulation , 1998, 1998 IEEE Second Workshop on Multimedia Signal Processing (Cat. No.98EX175).

[17]  O. Roeva,et al.  Information Hiding: Techniques for Steganography and Digital Watermarking , 2000 .