Research On Design And Application Of Fragile Watermarking Algorithm

How to ensure the authenticity and integrity of digital image is a research hotspot in the field of information security.Fragile watermark is a key technology to solve the authenticity and integrity of image because of its strong sensitivity to image tampering.This paper first introduces the basic theory of fragile watermark,the classification of fragile watermark,studies and analyzes the fragile watermarking algorithm based on local two value mode(LBP),and concludes that it can't detect copy paste and mosaic attack effectively.On this basis,the fragile watermarking algorithm is studied and implemented based on hash function and DWT transform.The main work of this thesis is as follows:1.Aiming at the existing fragile watermarking algorithm based on local two value mode(LBP),the copy paste and mosaic attack can't be detected effectively,and a fragile watermarking algorithm based on hash function is proposed by using the feature of hash function without collision.Experimental results show that the algorithm fully meets the requirements of watermark non-perceptual,and can detect malicious tampering in 100%.2.According to the rule that the size relation between wavelet high frequency coefficients does not change after JPEG compression,a semi-fragile watermarking algorithm is proposed.The algorithm information embeds the watermark information according to the size relation between the high frequency coefficients,and the algorithm can distinguish between accidental attack and malicious tampering.That is to say,the algorithm can pass authentication in the face of JPEG compression,filtering and other operations that have no effect on image content,and can't pass authentication in the face of malicious attacks such as cropping and dashes.Experimental results show that the algorithm has large embedding capacity,can effectively distinguish accidental attack and malicious tampering,has good anti-JPEG compression performance,but also can accurately locate malicious tampering.3.In order to recover the detected malicious tampering,a high quality recoverable semi-fragile watermarking algorithm is proposed by combining wavelet transform and digital watermarking technology,which can ensure the recovery effect while reducing the watermark embedding capacity and improving the image quality of the watermark.The algorithm puts the high 5-bit image wavelet low frequency coefficient of the original image as the recovery watermark information,combined with the wavelet low frequency coefficient of the high 5-bit image of the tampering image to realize the tampering detection,location and recovery.Experimental results show that compared with the existing algorithms,the algorithm has small watermark embedding capacity,high quality of watermark image,can effectively resist known counterfeiting attacks such as shearing,collage and graffiti,and can better realize the detection,location and recovery of tampered images.