I. Introduction
Data hiding embeds messages into digital multimedia such as image, audio, video etc through an imperceptible way. Such technology plays the important role in protecting the privacy, which can be roundly classified as robust watermarking [1] having the ability to resist many attacks, fragile watermarking [2], [3] being fragile to any modifications, and steganography [4] with the strong undetectability. From the application side, robust watermarking, steganography and fragile watermarking are mainly used for copyright protection, covert communication and integrity authentication respectively. A review of data hiding techniques and a few emerging innovative solutions using data hiding are well introduced in [5].