Firmware re

Checksums
see Checksum algorithms

EEPROM
see EEPROM access functions

security / encryption
It seems everything uses the same algorithm. Somewhere Nissan calls this algo "01", so I'll use that notation. It is used for on most known ROMs. Algo description and equivalent C code http://www.romraider.com/forum/viewtopic.php?p=102962&sid=92748181f9c23e0ad67ea5c1a5486984#p102962.
 * SID 27 key exchange
 * SID 36 RAM bootloader kernel download
 * SID 36 firmware payload download