Tamper Protection Digital Watermark And Its Application In DRM System

With the promotion of the demand for trusted communication and the awareness of copyright protection,the tamper protection of multimedia content has gradually come into people's perspective.Since the enhancement of multimedia content editing tools functionality and the operability,multimedia content tampering becomes extremely simple,especially for the image tampering.While the popular social network accelerates the spread of tampering with content,multimedia content tamper protection problems need to be solved.As an effective means of tamper-resistant,digital watermarking has been widely concerned.In this paper,the digital image as the main object of study,from the active tamper constraints and passive tamper detection both were studied the development of the current situation removable visible watermark and fragile watermark algorithm.By analyzing the existing problems,it proposed corresponding improvement and DRM model is designed based on dual tamper-resistant watermarking.(1)For the problem that existing removable visible watermark algorithm applies only to binary watermark,and that diversity and security is poor,the paper proposed an improved removable visible watermarking algorithm which supports for tamper-proof.By using chaotic map,the grayscale watermark was preprocessed and different versions of a visible watermark were obtained.Then the preprocessed watermark was embedded adaptively according to the human visual system.The results show that the algorithm satisfies the diversity of the watermark,and legitimate users can remove the visible watermark with the correct key and the original watermark,while illegal removal will lead to poor visual effects.The algorithm has a good active tamper function with restrictions and limitations.(2)For the problem that existing fragile watermarking has a poor uniformity and low sensitivity of tamper detection,an improved uniformity fragile watermarking algorithm was proposed.The authentication watermark of the image block is generated with MD5 and chaotic map,so any changes to a pixel in the block will affect the authentication watermark,and tamper detection capabilities are further enhanced by using layered testing.In addition,the recovery watermark and the trust watermark are also introduced.The results show that the algorithm not only has better uniformity and relatively higher tamper detection efficiency,but also can repair the tamper automatically and communicate trust objects to overcome the shortcomings of block certification.(3)The DRM model is designed based on dual tamper-proof watermarking and it can implement passive and active tamper protection of digital image content in the system.The uniform fragile watermark can locate the tamper position and estimate the tamper degree,and can maximize the value of the parts that are not tampered.Combined with the image block retransmission mechanism,it can improve the recovery capability of tampering.After tamper recovery is complete,removable visible watermark can be used to actively restrict and limit illegal tampering,while allowing legitimate users to remove the visible watermark.