Android - Is there a way to get platform.pk8 and platform.x509.pem the rom signed with?

Question

I was just curious if there is a way to get platform.pk8 and platform.x509.pem which are used to sign the rom inside the Android device.

My aim is no more than developing system applications for testing and using my self-owned devices on my desired purpose.

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For those who are not familiar with creating system apks: signing an apk with system signature [WITHOUT ROOTING]

Answer 1

No.

At least, not if the person building the ROM knows what they're doing.

From the docs (emphasis mine):

Each key comes in two files: the certificate, which has the extension .x509.pem, and the private key, which has the extension .pk8. The private key should be kept secret and is needed to sign a package. The key may itself be protected by a password. The certificate, in contrast, contains only the public half of the key, so it can be distributed widely. It is used to verify a package has been signed by the corresponding private key.

If your device has an unlockable boot loader, you could build and flash your own ROM, using a key pair that you created yourself. That way, you'll have the platform private key to use for your system app.