Fixed point in fractal image compression as watermarking

Conventional approaches to embedding digital watermarks I. Cox et al. (1997), are done by adjusting spatial pixel values or frequency coefficients. We propose a novel way to achieve attack detection by calculating the image´s fractal compression fixed point which is an approximation to the original image. After such transformation the fixed point image survives fractal image compression and is extremely sensitive to manipulations. A method to embed digital signatures into the fixed point is also presented in order to provide authentication.