The XOR key repeats every LCM(4,8) = 8 bytes, allowing trivial decryption if any 8-byte plaintext segment (e.g., known bootloader header) is known.

If you want to build your own "new" ROM, here is the technical workflow:

The tool will "repack" these system files into a single .rpkg file, which contains the necessary Z: drive and device-specific data for the emulator to boot the N70 interface. :