Confusion/diffusion capabilities of some robust hash functions

Perceptual hash functions have been recently proposed as cryptographic primitives for multimedia security applications. However, many of these hash functions have been designed with signal processing robustness issues and have not addressed the key issues of confusion and diffusion that are central to the security of conventional hash functions. In this paper we give a definition for confusion and diffusion for perceptual hash functions and show how many common perceptual hash functions do not display desirable confusion/diffusion properties.