Homebrew Question XCI Format info

[Deleted member 191657]

I was looking at http://switchbrew.org/index.php?title=Gamecard_Format to learn more about how the Switch handles Gamecards.

Looking at the structure I noticed some fields that aren't completely clear and I wanted to shed some light on them:

0x110 0x8 Package Id (used for challenge–response authentication)
What's a Package Id? Is it game dependant? Is there any way to derive it and/or is it related to titleID ?

0x10C 0x1 Title KEK Index (high nibble) and KEK Index (low nibble)
To which keys is this related to? What do they encrypt/decrypt?

Initial data ( http://switchbrew.org/index.php?title=Gamecard_Format#Initial_Data )
Where is it located in the XCI file?


Thanks in advance for any answer!