On the possibility of constructing meaningful hash collisions for public keys

It is sometimes argued that finding meaningful hash collisions might prove difficult. We show that for several common public key systems it is easy to construct pairs of meaningful and secure public key data that either collide or share other characteristics with the hash collisions as quickly constructed by Wang et al. We present some simple results, investigate what we can and cannot (yet) achieve, and formulate some open problems of independent interest. We are not yet aware of truly interesting practical implications. Nevertheless, our results may be relevant for the practical assessment of the recent hash collision results. For instance, we show how to construct two different X.509 certificates that contain identical signatures.