Forging $_POST vars

[msore]

I am working with a company that builds windows C based software. We will be putting a link in the application that will point to a PHP website.

For security reasons we only want registered software users to get to this site (with out setting up a user/pass). Hence, we do not want to place URL/$_GET vars in the link.

How can I forge post data to hide the authentication data so that they cannot pass the URL to someone else??

Thanks

[victordb]

What software are you using to program your C programs?

[victordb]

I've thought of a way possible that could be done probably in any programming interface. I got the idea when logging into MSN, have your program create a temporary file that is deleted as soon as it is opened and have in that file Javascript code that sends a post to a script so that the user only sees the page for a split second before he is redirected and the page is deleted.