Is xcassets secure?

Hi everyone!

Let me explain my problem a little bit. We are going to develop and ship Font-selling app with a brand-new System Fonts Api in iOS 13. If I get it correct from WWDC'19 presentation as a developer I have to provide all Fonts that I want to sell in my app within the assets catalogue in order to submit an app for reviewal processhttps://developer.apple.com/videos/play/wwdc2019/227/

So my customer is pretty aware of any kind malicious ipa-file decomposition in order to achieve illegal access to the resource-folder. Can you please give any advice on this topic? Is it possible? Should/May I add any additional crypto-protection to my files?

Thanks Andrey!