How to compress directory with NSData category?

I played with the application, and I wanted to add the ability to compress the directory and its children. I found the CocoaDev category, often mentioned here, but ended up settling in the category combined for Molecules . My problem is less with the compression category and more with the conversion of the directory to a valid NSData object. I want people to be able to deflate a file using any application. I looked at NSFileManager and serialized the contents of the directory and compressed it, but I suspect that this will prevent the devaluation of the archive.

Where am I mistaken? Is NSData Enough?