Questions about generating keys (hash firewalls)

[Robert J. Hansen]

Oskar L. wrote:
> I only meant to point out that a birthday attack would have a much better
> chance of finding a collision than a second preimage attack. I'm sorry if
> I made it sound trivial, I know it's not. I just tried to give an example
> of how it works that would be easy to understand.

Well, except that your attack isn't a birthday attack.

A birthday attack involves making a ton of different messages and
checking _all_ messages created to find _any_ collision.

Your attack involves taking one particular message and creating
permutations of it, one after another, looking for a collision with your
particular message.