Overview of Audio Watermarking Algorithm against Synchronization Attacks <s> B. Display Synchronization Scheme <s> A blind audio information bit hiding algorithm with effective synchronization is proposed in this paper. The algorithm embeds synchronization signals in the time domain to resist the attacks such as cropping while keeping the computation for resynchronization lower. The watermark is placed in blockwise DCT coefficients of the original audio exploiting the HAS (Human Audio System) features. To lower the bit error rate of the watermark in extraction, error-correcting coding is applied. The experimental results show that the hidden imperceptible watermark is robust to the attacks caused by additive noise, MP3 coding, and cropping. <s> BIB001 </s> Overview of Audio Watermarking Algorithm against Synchronization Attacks <s> B. Display Synchronization Scheme <s> Synchronization attack is one of the key issues of digital audio watermarking. In this correspondence, a blind digital audio watermarking scheme against synchronization attack using adaptive quantization is proposed. The features of the proposed scheme are as follows: 1) a kind of more steady synchronization code and a new embedded strategy are adopted to resist the synchronization attack more effectively; 2) he multiresolution characteristics of discrete wavelet transform (DWT) and the energy-compression characteristics of discrete cosine transform (DCT) are combined to improve the transparency of digital watermark; 3) the watermark is embedded into the low frequency components by adaptive quantization according to human auditory masking; and 4) the scheme can extract the watermark without the help of the original digital audio signal. Experiment results shows that the proposed watermarking scheme is inaudible and robust against various signal processing such as noise adding, resampling, requantization, random cropping, and MPEG-1 Layer III (MP3) compression <s> BIB002 </s> Overview of Audio Watermarking Algorithm against Synchronization Attacks <s> B. Display Synchronization Scheme <s> Synchronization is still one of the most important issues in digital watermarking. Many attacks do not remove the ::: watermark from the cover, but only disable the synchronization between the watermark and the detector. Most ::: watermarking algorithms feature some synchronization strategy, but especially in audio watermarking this may not be ::: sufficient to fight de-synchronization attacks: As the watermark is embedded over a given length of audio data, a good ::: synchronization at the starting point of the retrieval process may be lost during retrieval. An example for this is time ::: stretching, where the effects of playback speed modification sums up during retrieval. We introduce a novel ::: synchronization approach applying passive audio fingerprinting to synchronize each watermarking bit individually. ::: Storage of the fingerprint values is not necessary in our approach, improving the usability compared to existing solutions ::: in this area. <s> BIB003
The display synchronization method embeds synchronization data except embedding the watermark information. The synchronization data is named synchronization flag. The synchronization flags generally use m-sequence or Barker code. Using the method, the detection algorithm finds the synchronization flags, compares these flags with the embedded flags to identify the attacks which the audio signal is suffered, detects the watermark information after the attacks are reversed. In BIB001 , the algorithm embedded synchronization signals in the time domain to resist the attacks such as cropping while keeping the computation for resynchronization being lower. The experimental results show that the hidden imperceptible watermark was robust to the attacks caused by additive noise, MP3 coding, and cropping. In BIB002 , the scheme adopted the barker code with special autocorrelation function as synchronization flags. In  , the scheme embedded the synchronization codes and the watermark information into the low frequency coefficients in discrete wavelet transform domain. By exploiting the time-frequency localization characteristics of DWT, the computational load in searching synchronization codes had been reduced, thus resolving the contending requirements between robustness of hidden data and efficiency of synchronization codes searching. In BIB003 , a novel synchronization approach applying passive audio fingerprinting to synchronize each watermarking bit individually. Storage of the fingerprint values is not necessary in the approach, improving the usability compared to existing solutions. This approach causes three problems: (1) The embedding of the synchronization data increase the embedding capacity to decrease the quality of the audio signal; (2) It is very easy to produce the false alarm rate; (3) It is very easy to cause the security issues. In general case, the same synchronization flag is used to a series of different audio signals, which eases the task of the detector but can be easily found and removed by the attackers.