[Help] How to use linux kernel crypto

Hi List, My transparent encryption filesystem goes fine with wrapfs framework. Just now I finished coding the Android Locking Screen application that works with the kernel filesystem module. But I get stuck again when it come to using AES to encrypt and decrypt data of files. I've read the documents in kernel/documentation/crypto/ but found nothing helpful ( Wrong place? :-S ) Would anyone introduce me to a demo showing how to use it , or some other documents? Or maybe I need a third-party crypto that can work in the kernel. Thanks! All the best! Freeman Zhang