Fragile Watermarking for Image Authentication Using QR factorization and Fourier Transform

摘要

Image authentication technique is one of the important methods for a large number of multimedia applications. When a digital image is passed over non-secure channels such as the Internet, it may be changed and manipulated. For some important images such as military and medical images, these manipulations are very harmful and such images should be protected against them. There are several ways such as fragile and semi-fragile watermarking to authenticate images from malicious attacks. This paper presents a fragile watermarking algorithm for image authentication by using QR factorization and Fourier Transform (FT). By applying Fourier transform to host image, frequency domain which causes visual quality in watermarking is achieved. After applying FT, it is factorized by QR decomposition. QR factorization is also applied to watermark image. After factorizing both images, a coefficient of the upper triangular matrix R from watermark image is embedded to the upper triangular matrix R from host image. So a sign of the watermark image is hidden in the host image. This method is a fragile watermarking and it is sensitive to a little attack. So if an image is attacked over the Internet, the watermark image can not be extracted and it means that it has been attacked and it helps us to recognize if an image is changed after being transmitted over the Internet. The experimental results show that this method is sensitive to every weak attack and extraction part can not extract watermark image if it has been attacked.