查看文章

Using watermarking techniques and digital signatures can better solve the problems of digital images transmitted on the Internet like forgery, tampering, altering, etc. In this paper we proposed invisible fragile watermark and MD-5 based algorithm for digital image authenticating and tampers detecting in the Discrete Wavelet Transform DWT domain. The digital image is decomposed using 2-level DWT and the middle and high frequency sub-bands are used for watermark and digital signature embedding. The authentication data are embedded in number of the coefficients of these sub-bands according to the adaptive threshold based on the watermark length and the coefficients of each DWT level. These sub-bands are used because they are less sensitive to the Human Visual System (HVS) and preserve high image fidelity. MD-5 and RSA algorithms are used for generating the digital signature from the watermark data that is also embedded in the medical image. We apply the algorithm on number of medical images. The Electronic Patient Record (EPR) is used as watermark data. Experiments demonstrate the effectiveness of our algorithm in terms of robustness, invisibility, and fragility. Watermark and digital signature can be extracted without the need to the original image.