Secure Fragile Watermarking Algorithm with Tampered-pixels Localization

Fragile watermarking is used to detect the authentication and integrity of digital media.The tamper detection performance and the security of a fragile watermarking scheme are two important evaluation measures.This paper proposes a secure pixel-based fragile watermarking scheme,in which the watermark data of each pixel is generated and embedded based on the secret key.Using the pixel-neighborhood comparison,the tamper detection performance is improved without increasing the watermark payload.In the proposed scheme,the chaos system is used to generate the binary watermark data according to the content of each pixel in the original image.The improved security binary watermark by scramble encryption was embedded into the least significant bit of the image data.In tamper detection process,the validity of the test pixel is determined by comparing the number of the inconsistent pixels in a pixel-neighborhood of it with the predefined threshold.The method of the dynamic threshold selection and the relationship between the tamper ratio and the probabilities of false acceptance and false rejection are discussed.Theoretical analysis and simulation results show that the proposed method can distinguish the modifications on the content from the watermark and resist the collage attack,and detect the tampered pixels with a probability of nearly 1.