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With the rapid development of network technologies and digital devices, the delivery of digital multimedia becomes faster and easier. However, distributing digital data over public networks is not reliably safe because of the risk of incurring leaks of sensitive information. Therefore, the protection of digital data, especially sensitive data, has become an important issue.
As an important way to protect secret information, data hiding technique has been extensively studied recently. Data hiding is different from classical encryption, which hides secret information into a cover object (e.g., image, video, audio, text) to create a stego medium with little distortion (Provos & Honeyman, 2003; Li et al., 2010). In general, data hiding includes digital watermarking and steganography(Petitcolas et al.,1999) .Digtal watermarking is used for copyright protection (Nikolaidis & Pitas, 1998; Lin et al., 2001), authentication (Lin & Chang, 2001; Lu & Liao, 2001), and transaction tracking (wong et al.,2005), etc., whereas steganography undetectably alters a cover object to conceal a secret message(Cox et al.,2007). Usually, three different aspects in steganographic systems contend with each other: payload, imperceptibility, and robustness (Langelaar et al.,2000; Sabeti et al.,2010). The tradeoffs of these aspects vary with the application domains and users’ requirements.
Many steganographic techniques about embedding data into images have been proposed. For example, Wu and Tsai (2003) introduced a steganography based on pixel-value differencing, which hided large amount of secret bits into an image by modifying the difference values between pairs of adjacent pixels. To enhance the security, Zhang and Wang (2004) proposed a modified scheme by selecting the length of the intervals randomly. Chen et al. (2010) proposed a steganography mechanism using hybrid edge detector. Hsiao and Chang (2011) proposed an adaptive steganographic method based on the measurement of just noticeable distortion profile measurement.
In general, embedding secret data into a cover image often leads to the degradation of embedded image and the original image can’t be recovered. However, in some applications, such as military image systems, medical diagnosis, and art works, it is critical for an original image to be recovered or reversed after the hidden data are extracted. This technique, which is called distortion-free or lossless data hiding, has drawn tremendous attention in recent years. Tian (2003) proposed a reversible data embedding scheme with high payload and good imperceptibility and then Alattar (2004) generalized Tian’s scheme. Kim et al. (2008) introduced histogram based reversible data hiding technique by using subsampling, and some other reversible image steganographic schemes, such as (Lee et al.,2008; Kieu & Chang,2009; Wu et al.,2010; Chang & Kieu,2010), are also introduced recently.