# Adaptive and Blind Audio Watermarking Algorithm Based on Chaotic Encryption in Hybrid Domain
## 1 Introduction  
With the rapid development of the Internet and multimedia technologies, it is convenient to transmit digital information all over the world quickly. However, the information security problem has become a global issue to be solved [1; 2; 3]. A digital watermarking algorithm is an effective method to protect media content in the fields of copyright protection, fingerprint identification, broadcast monitoring, medical security, data authentication and so on. In recent years, it has become a hot topic in the field of communication and information security [4; 5]. A digital watermarking algorithm can be applied to different multimedia carriers such as audio, image [6; 7; 8], data and video [9]. Because the audio media contains less redundant information, it is difficult to develop an audio watermarking algorithm. With the widespread use of audio media on the network, people begin to focus on the research of an audio watermarking algorithm. Over the past decades, many audio watermarking algorithms have appeared in different domains, such as the time and transform domains. In general, the time domain watermarking algorithm is easy to implement, but less robust in combating various digital signal processing attacks [2; 4], such as the algorithms in literature [10; 11]. Compared with the time-domain algorithms, the algorithms in the transform-domain, such as the discrete Fourier transform (DFT) [12; 13; 14], discrete cosine transform (DCT) [15; 16], discrete wavelet transform (DWT) [17; 18; 19; 20; 21] and singular value decomposition (SVD) [22; 23] and so on, are more robust because they explore human auditory properties and the features of audio signal. [PERSON] [13] presented a blind watermarking algorithm by DFT for stereo signals. [PERSON] [14] used audio signal as a carrier to transmit the data that needs to bekept secret in the DFT domain. DCT has the characteristics of compressing the signal energy to its low frequency coefficient, which makes it widely used in data compression. [PERSON] [15] designed an audio watermarking by modifying the vectors in the DCT domain. [PERSON] [16] designed an audio watermarking method in a multilayer framework to improve capacity in the DCT domain. DWT decomposes the audio signal into different frequent bands both in the time and frequency domains, so the watermark algorithms designed by DWT are usually very robust. [PERSON] [17] proposed an audio watermarking algorithm to solve the problem of content authentication and recovery in the encrypted domain. [PERSON] [18] utilized DWT to design an adaptive method with poor robustness for resampling and low-pass filtering. [PERSON] [19] proposed an audio watermarking algorithm by adjusting the high-frequency wavelet coefficients of each audio segment in the DWT domain. [PERSON] [20] proposed a blind watermarking scheme to embed a binary watermark into a low-frequency approximation sub-band based on lifting wavelet transform (LWT). [PERSON] [21] used the norm ratio of approximate coefficients to design an audio watermarking scheme to balance the performance of the algorithm in the DWT domain. All of these algorithms are designed in a single-transform domain, and there are many schemes designed in hybrid domains in recent years. [PERSON] [24] proposed a scheme for audio signal tamper recovery and location tampering based on DWT and DCT. [PERSON] [25] proposed an audio watermarking algorithm to achieve invisible data hiding based on DWPT, SVD and quantization index modulation (QIM) hybrid domains. In general, the watermarking algorithms designed in the hybrid domain have better performance than those designed in a single-transform domain according to the experimental results of the above literature. An audio watermarking algorithm can be evaluated by four indexes which are robustness, imperceptibility, capacity and security [4; 16]. Imperceptibility means that listeners cannot distinguish the difference between the original audio and the watermarked audio.