-
Add your cert normally, it will be stored in your personal store and android will ask you a pin/password... Proceed
-
With a file manager with root capabilities, browse files in /data/misc/keychain/cacerts-added. You should see a file here, it's the certificate you have added at step 1.
-
Move this file to system/etc/security/cacerts (you will need to mount the system partition r/w.
1. Mount system RW: mount -o rw,remount /system
2. Mount system RO: mount -o ro,remount /system
Copy user CA-Certificate into System CA-Certificates (https://android.stackexchange.com/questions/110927/how-to-mount-system-rewritable-or-read-only-rw-ro)
--> cp /data/misc/keychain/cacerts-added /system/etc/security/cacerts/
https://\<firebaseProjectName\>.firebaseio.com/.json
--> Header.Paylod.Signature
--> Header => Algorithm used in Signature
--> Paylod => Claims (User Data)
--> Signature => HMAC_SHA256(Base64.encode(header)+"."+Base64.encode(payload),secret)