SKSA (Secure Kernel / System App) is the "Upgradable Operating System" of the iQue Player, the main software that runs on the device.
- Secure Kernel: the 'boot1' of the iQue. Doesn't ever seem to change between SKSA versions, so might be similar to the Wii boot1; the hash of it is checked against a stored hash in Virage2.
- System App 1: Consists of a ticket, followed by the actual SA1 data. Most SA1s are just the iQue Menu, though some seem to be factory/graphics tests. SA1 seems to be responsible for handling USB comms too.
- System App 2: Also has a ticket, followed by SA2 data. Unknown purpose, in SKSAs that have an SA2 the SA1 size is greatly reduced compared to single-SA SKSAs, presumably they moved some data from SA1 into this, but it seems like dual-SA SA1s can run without needing the corresponding SA2?
The format of the SKSA is simple: a 64KiB SK, followed by SA1 (ticket + data), optionally followed by SA2 (ticket + data):
|0x0||0x10000||encrypted bytes||Secure Kernel|
|0x14000||(sa1ticket.ContentSize)||encrypted bytes||SA1 data|
|0x14000 + sa1ticket.ContentSize||0x4000||ticket||SA2 ticket|
|0x18000 + sa1ticket.ContentSize||sa2ticket.ContentSize||encrypted bytes||SA2 data|
On NAND the format is slightly changed however: instead of storing the SA1 & SA2 data exactly as stored in the cached SKSA, the data is instead reversed in 0x4000 byte blocks (though tickets are unaffected). The NAND spare data is used to store pointers for these blocks, to allow for skipping any bad blocks in the SKSA area.
The BBFS FAT table also sets the SKSA blocks to 0xfffd (reserved), to ensure that no files will overwrite them.
A spreadsheet of the different SKSAs that have been tested (whether it boots, what happens when it boots, etc) is available here.
Jan 2004 update
Added Settings(管理) menu and "i-Timer" Smart Clock, allowing parents to set time limit on gaming and allowing games to use real-world time.
Sept 2004 update
Added iQue@Home support to the console.
This update is most likely corresponds to the SKSA version 1092 as it is the first version to have iQue@Home USB support.