Verification Of Platform-signed System Apps


Apr 12, 2018
Sorry if off-topic, but I think this is the best place to ask about it.

I want to modify a MIUI ROM with a self written application that should have system privileges. To achieve this, the apk must be signed with the platform-key.
I assumed that I can go into the system directory and exchange this key and the associated certificates with my own generated key. But the so created ROM does not boot on my Redmi 4x.

When and how is this platform-signature verified on MIUI? There must be some kind of reference that is compared with the apk signatures.

I thought that this would be a common task in ROM modding but there is extremely few information about it on the web.