Finding collision resistant hash functions

[Mike Rosing]

On Mon, 7 Jul 2003, Sarad AV wrote:

> Is there a polynomial time  algorithm that will find
> collision hash functions or how are we supposed to
> find collision free hash functions?What exactly is the
> difficulty in finding collision free hash functions?

It can't be collision free if the number of input bits exceeds the number
of output bits.  Think about it, it should be obvious!

Patience, persistence, truth,
Dr. mike