DRM encrypted JAR file in a s40 Nokia Phone

I need to know how DRM actually works in active files(such as programs,games) in s40 enviroment.

I tried to build my own drm protected files with NMIT(Nokia Mobile Internet Toolkit). But results are not similar to file i copied from phone to computer. The file has only readable part like "a开发者_开发知识库pplication/java-archiveflcontent@fl.contentid.s40drmv1#" and other parts all giberish. If it is encrypted, how (with what key) is it decrypted prior to execute? And finaly is the program responsible to decrypt itself with former payload or is that responsibility of the phone os?

Thanks in advance.

It is likely that those files are protected with Open Mobile Alliance (OMA) DRM 1.0. See OMA Digital Rights Management V1.0 for the specifications.