Data Hiding in Digital Audio by Frequency Domain Dithering - Computer Network Security - page 383

Data Hiding in Digital Audio
by Frequency Domain Dithering
Shuozhong Wang, Xinpeng Zhang, and Kaiwen Zhang
Communication & Information Engineering, Shanghai University, Shanghai 200072, China
[e-mail],[e-mail],[e-mail]
Abstract. A technique that inserts data densely into short frames in a digital
audio signal by frequency domain dithering is described. With the proposed
method, large embedding capacity can be realized, and the presence of the hid-
den data is imperceptible. Synchronization in detection is achieved by using a
two-step search process that accurately locates a PN sequence-based pilot signal
attached to the data during embedding. Except for a few system parameters, no
information about the host signal or the embedded data is needed at the re-
ceiver. Experimental results show that the method is robust against attacks in-
cluding AWGN interference and MP3 coding.
1 Introduction
As a result of the rapid development of digital technology and computer networks,
digital multimedia materials are widely used and disseminated. Since digital informa-
tion is easy to copy, protection of intellectual property rights has become a serious
concern. As a means of IPR protection, watermarking [1-2] has attracted much atten-
tion. In addition, information-hiding techniques have also found applications in covert
communication, or steganography [3]. The aim is to convey information under the
cover of an apparently innocuous host material, which differs from traditional encryp-
tion as not only the contents of the transmitted data are kept unintelligible to eaves-
droppers, but also the very fact that communication is taking place is hidden. Clearly,
a sufficient data capacity is an important factor in covert communication. This is in
contrast to the IPR protection-oriented watermarking in which robustness is a primary
specification.
Watermarking in digital audio has also received considerable research interests.
Many techniques [4~6] have been proposed based on the characteristics of digital
audio signals and the human auditory system (HAS). Some time-domain methods can
hide a large amount of data but are not robust enough. Among the frequency-domain
techniques, phase coding makes use of the insensitivity of HAS to the absolute phase
in the Fourier transform coefficients. Inaudible embedding is achievable with a small
phase change representing the embedded data. In echo data hiding, the hidden data is
carried by parameters of an introduced echo (reverberation) close enough to the origi-
nal signal.
This paper describes a data hiding approach that uses an audio signal as the host.
Since HAS is very sensitive to slight distortion, tiny changes in the audio signal may
be perceptible to normal listeners. Consequently, the achieved embedding capacity in