Robust Speech Watermarking Algorithm Against Recapturing Attacks

Watermarking provides a technical mean for copyright protection of digital audio. However, with the popularity of recording equipment, recapturing attack has become an effective method to remove audio watermarks. In order to improve the security of the watermarking system, we propose a robust speech watermarking algorithm against recapturing attacks. Firstly, we define the discrete cosine transform coefficients logarithm mean (DCT-CLM) feature and get the conclusion that the changes of DCT-CLM feature are very small after recapturing attacks. Secondly, Frame number and watermark are embedded together in frames by quantifying the DCT-CLM feature. Frame number is used to resynchronize watermarked speech after the signal is subjected to de-synchronization attacks. If watermarked frame is synchronized, we extract watermark bits from the frame for resource tracing. Compared with other speech watermarking algorithms, the algorithm proposed in this paper is not only robust against de-synchronization attacks, but also robust against recapturing attacks.