"The path forward is clear, and I don’t see much benefit to looking backwards." - It's always better to struggle rather than let yourself sink. Especially when there is no alternative. Sometime legacy stuff can't be update, I'll go bury it and dig my hole. Anyway, thank you for your replies.

@Scott Thank you !

Hi @eskimo The bug report id : FB13690599 Category was used for long time ago, in old project, in legacy code, all can't be updated each time the system is updated. I knew about the namespace and all stuff in objc/runtime.h but i can't imagine that system's component can play with that over the app without caution.

Note: in the existing app if the user didn't go in a part with a WKWebView, the SHA256 function stay mine. If he navigate in the app with a call to WKWebView, the function NSData sha256 is replaced. i use WKWebView only for static html in ressources (not external loading for network)