Wavelet Domain Digital Image Watermarking Based On Spread Spectrum Mechanism Study

With the advent of the digital age, the content of the media gradually changes from the analogy to digit.But the essence between the content of the analogy and digit is that firstly the analog is concerned with media rather than the digit;secondly, the digital content can overcome the shortage of content replication and is very simple instead of reducing the debasement of quality and needs the content of the transport much lower; finally, it is the most important for the digital technologies to greatly promote the development of new business model development. Digital technology makes multimedia message, such as an image or text or audio or video stored, copied and disseminated, and becomes very convenient. Although the problem between copyright piracy and conflict also becomes increasingly serious social issues. The existing copyright system always has an access to a password authentication technique, such as use DVD discs. the security of passwords, However, merely uses a password technology and cannot be completely solve the problem of copyright protection, and technology in the data can be only from the sender to the receiver transfer process, and the encrypted data can not help the seller supervisor the legitimate users to deal with the contents of the code and can protect the transfer of technology content, which is decrypted with protection.To solve the technical data protection, a new kind of valid digital rights protection and data security maintenance technology------the digital watermarking has been developed.Spread spectrum as a new type of communication has the advantages of resisting the interference and the noise and holds a low power density and good security. It carried out the transmitted signal frequency with the expansion of the bandwidth but far beyond its channels of communication in general sense of the bandwidth. To receive signals synchronizing with an expansion and relate to the resumption of data holds the same random sequence at the receiving end. Spread spectrum technology conceived in the random sequence is very similar to the nature of white noise, and functions have sharp features. Therefore, pseudopodia are usually made of the shift binary register, and m sequence is the most usual type of random sequence and has a fine performance. It is very easy to produce the relevant characteristics and rarely random, but each other in features isn't very good. To recognize a sequence of security for m and DWT domains against cropping, translating and compressing attacks was relatively poor. The algorithm first selected the pseudo random sequence modulation for the periodic sequence of continuation, and then encrypted. Taking into account the characteristics of human visual system HVS, the positions and strengths of embedding into the original image which used the same chip rate coefficients of the wavelet transform domain were obtained. Selecting spread spectrum sequence determined the maximum coefficients of the wavelet transform domain and the key period sequence of watermarking. The experimental results show that the algorithm is more secure and robust against geometric distortions and general image processing operations. Although the translation has certain limitations, you can still better detect of the embedded watermarking.