Platform.x509.pem platform.pk8 files

Where can I get the platform.x509.pem platform.pk8 files for the latest version (https://builds.96boards.org/releases/dragonboard410c/qualcomm/android/15.06/) of the Android Built in the Dragonboard?.

This in order to be able to sign apks in order to get more permissions.

Regards

Anybody has these files for the 15.06 version?

How could I get them?

In fact, I am trying to write a system application so, according to what I have read, I have to sign it with the developer’s digital keys in the build tree files (in the build/target/product/security/ platform.x509.pem platform.pk8). Does anyone know a way to get these files?