I just created this "form key" library, need suggestions

[eluser]elvix[/eluser]
There's a couple of CSRF libraries floating around already (same concept, CSRF = cross-site request forgery). You might want to check those out.

One benefit is that they extend the input controller, and the form helper, adding the CSRF protection transparently to all your forms. There's also a token generator which is useful to get CSRF working with Ajax scripts.