Improved Algorithm Of Digital Watermarking Based On JPEG Encoding

With the development of World Wide Web, any network user can copy and transfer information easily, which makes data transmission quite convenient. At the same time, security problems follow. How to protect copyrights of all kinds of multimedia productions, such as video, audio etc. becomes an serious problem.Cryptography and digital watermark are two effective measurements. Cryptography has already been demonstrated by integrated and rigorous theories, which can be implemented conveniently and unfailingly. But during the application of cryptography, the sender and receiver must share the cipher. Besides, once the encrypted data is cracked, security is nothing. The form of encrypted data has changed also. Opposite to cryptography, the technology of watermark is able to add some kinds of information, such as authors, copyrights etc. to video and audio data. Qualified user can validate the copyright by getting the information. But unqualified user can't obtain the information in the multinomial time. Therefore, watermark has unexampled superiority over cryptography in the part of multimedia data protection.In this paper, image information compression and the quiescence image compression international standard JPEG are introduced firstly. The basic knowledge of watermark is followed. Based on the following principals simply implement, simple theory security, traditional watermark algorithm is improved through analyzing it . Experiment results indicate that the improved algorithm can undergo familiar attacks.