如何播放带有模糊文件名的文件？

I am making an app that downloads videos to the documents directory and plays them with MPMoviePlayerController. To help prevent the videos from being taken off of the device and played, I am going to obfuscate the file names. Let's say I want to play a movie marked "movie.blah" when the real file extension is "mov". How do I get this to play? Do I have to temporarily rename it to "movie.mov" and then change it back when it is done playing? Thanks for your help.I am making an app that downloads videos to the