Semi-fragile Blind Watermark Based On DCT Transform

In course of development of multimedia and network,it is easy to getting all kinds of multimedia information.Though digitized multimedia has any advantages,but it is unavoidable illegally copied and tampered,which makes its information copyright protection a problem to be solved urgently in networked environment.Watermarking technology is an effective method to image content authentication and copyright protection,which has been attended widely.After profound researching of current digital watermarking technology in worldwide,This theme proposed a Semi-fragile Blind watermarking algorithm based on DCT.This algorithm splits the original image to blockes and do DCT transform,uses random function create a bi-level sequence to get two different keys.Useing keys to get watermark,it achieves blind detection.This algorithm doesn't modify the original image,so it implements the transparency of digital watermark.The theme gives the experiment of the algorithm on Matlab in the end,and it shows that the algorithm can guarantee the unperceivability and transparency of the digital image.The experimental result analyses that has good robust against JPEG, cropping,and frangibility against the attack of Filtering and noisy,so beseem to selective authentication for image.