Could you hint how to create .keystore properly? I tried using platform.pk8 and .x509.pem files from nxp/android_build/build/make/target/product/security like below
openssl pkcs8 -inform DER -nocrypt -in platform.pk8 -out nxpimx8qmaaos12-platform.key
But when release.apk is signed with jarsigner or apksigner and app is deployed over ADP we get an error in app startup: "The app is not signed with a valid platform signature. The Car API back end cannot work with an unsigned app."
In NXP Android release, there are created keys/certs in “device/nxp/common/security/” (platform.pk8 and platform.x509.pem). Are you using keys from this location?
The apksinger tool supports signing APKs with keystore file or with the private key file and certificate file separately. Below are some useful links may be helpful: