So, custom Infotainment firmware may be reasonably possible after all.

[joegr]

Looks like the key that Hyundai uses for Infotainment updates is now known...

Hyundai Uses Example Keys for Encryption System - Schneier on Security

This is a dumb crypto mistake I had not previously encountered: A developer says it was possible to run their own software on the car infotainment hardware after discovering the vehicle’s manufacturer had secured its system using keys that were not only publicly known but had been lifted from...

www.schneier.com

 

[JEdwards]

This was a rookie mistake by a small programming team that understood the need to develop a low level encryption framework, and lacked knowledge of how to choose and manage encryption keys.

This is pretty trivial to fix in the future (and might already have been patched).

I initially found it strange that the 05/04/2022 release was followed by a 05/23/2022 release for many newer Genesis head units. I would not be at all surprised if the unencrypted contents of those two builds was identical, but the encryption used on the compressed tar-balls was different because that patched that security hole.