Syscon Update

= Structure =

Ernie updates are stored in a packet format.

Packet Header
Any update packet has a common header structure.

Packet size varies depending on the hardware revision of Syscon: Renesas 78K0R/Kx3: 0x800 Renesas 78K0R/Kx3-L: 0x400 Renesas RL78/G13: 0x400

0x01
Version packet.

This packet is update header field.

Ernie Version and Hardware Info from a few PUPs:

0x02
Key revision packet.

This packet embeds the encryption key revision used to decrypt the Syscon update packets.


 * Firmware Type 0 is for Renesas 78K0R Proto. It is supported since at least FW 0.931 (FW 0.902 doesn't support it) until FW 1.692. It is for Fat PSVita prototype.
 * Firmware Type 1 is for Renesas 78K0R. It is supported since about FW 1.00. It is for most Fat PSVitas and for PSTV.
 * Firmware Type 2 is for Renesas RL78. It is supported since FW 2.50. It is for PSVita Slim Syscon.

0x03
This packet is special because it is not embedded in Syscon Update SPKGs. It is generated in ARM kernel and sent to Syscon with Syscon command 0x1185.

It is not present on FW 0.931.

0x10
Encrypted segment packet.

Segments are concatenated before being AES128CBC encrypted/decrypted.

0x20
Hash packet.

= Ernie Update steps =


 * ARM PSVita updater arrives at last step: Ernie update.
 * ARM PSVita updater decrypts Ernie update SPKGs til it finds one whose Hardware Info matches.
 * ARM PSVita updater sends the encrypted segments directly to Ernie using some command 0x1181.
 * ARM PSVita updater sends the hash directly to Ernie using some command 0x1184.
 * Ernie decrypts concatenated received segments using AES128CBC.
 * Ernie computes sha1 over the decrypted concatenated data and compares with the received hash.
 * Ernie installs the update using the decrypted data.