Digging through the deeper settings of the Android headunit can bring up some questions, one of them being, ‘What are the user/release keys’?
Android at heart
Your Android headunit is running a version of the Android operating system. This OS is very similar to the version on your phone but tailored to work specifically on that make and model of the headunit, just as each model of the phone has a slightly different version of Android that fits the different phone hardware perfectly.
The keys are cryptographic encryption keys. These encryption keys are crucial to the security of the Android operating system. The whole permission system is based on encryption keys. Apps can only interact with each other if the encryption keys have been shared. Your information will be safe if the app developer has not shared the keys. Play store updates or sideloading apps to update will compare encryption keys; without a match, the app won’t update. This protects the app data from fake updates because the keys don’t match.
These encryption keys also secure the operating system from rogue updates. The keys must match for an OTA or file update to be accepted for the OS (should one be released).
Test keys are only used for in-house testing of apps and Android builds. They are not secret; they are included with the Android open-source code. These test keys are ideal for developing apps not ready to be released to the public domain. You should never see the test keys used unless you develop Android-based software.
The Release Keys are the secret keys that secure the OS or the app. They have been released to the wild and are there to do their job of securing code. You can’t do anything with the user/release keys other than know they are there, doing their job silently in the background.
Why show the user/release key?
The key name is shown, and the file is locked away in the storage. It is not helpful to you using your Android head unit, so this information is hidden away. It may be helpful for Android development, but only if you have the master key to the encryption keys and only the developers have those.
Public Key Encryption
The Android user/release and test keys are based on the clever Public-Key Encryption idea. This system uses two encryption keys: public and private (secret). The keys are linked in a one-way cryptographic function. The public key is not secret, but the private key should only be known to the creator of the key pair. Code and apps are signed with the private keys and checked (verified) with the public key in the device.