Encryption and decryption of the Android extension file

Question

I successfully downloaded and published the Android app + apk extension file (with the .obb format, but actually -.zip) on Google Play. I would like to create some protection for him. Is there a way to do this to achieve this without using external jar classes like zip4j?

In my obb file, I have some videos (from .mp4) that I need to use to work with my media player. I want to do this so that only my media player can read the obb file.

Thanks.