You can download the JaPCrypt class, with the documentation and examples on how to use the class, by clicking here
Oh, remember it's for PHP5. Minor changes are required to be used with PHP4.
A documentation of the class generated by phpDocumentor
can be found here
A demo on how the application works can be found here
To contribute to the project by submitting patches, documentation, features request, bugs, whatever, just drop me a mail to gerardo linux.it (put the right symbol in the right place, it's not hard ;).
To vecna (vecna delirandom.net) for suggesting me some cool tricks and implementation hints.