@zecoxao has released siscon which is a Syscon firmware decrypter for PS4. I've checked the source code and it requires three key related files; sys-key, sys-iv and sys-cmac which are not included. However, some keys (mirror) where leaked in previous story about the PS4 Syscon.
created this just for shits and giggles. decrypts syscon fw updates from ps4 devkit consoles (you need to provide the keys yourself, but they're not hard to find)