Windows
- download cmder. I find it easier to use OpenSSL and nix comands through cmder without having to install anything. Just download, extract the zip, and runcmder.exe
Android
- it must be rootedAndroid
- you need a file manager with root capabilities. I like using Amaze
I haven't tested if all these steps are required. I strongly suggest you follow them to generate a valid certificate file using the same structure as Android's.