One-way functions and Security

The example custom login system that I posted in the samples forum seems to have caused some misunderstanding. It stores passwords and user IDs in an encrypted form. I never assumed that it would be difficult to get the encrypted passwords out of the file. That is the very reason that it was encrypted in the first place. By encrypting it, it becomes useless to the hacker. You might think that by getting this data, and knowing the algorithm that was used to generate it, that it is a trivial matter to create an inverse function to decrypt it. Not so! That is the whole point behind one way functions. They have no inverse. I didn