Please can someone explain the architecture of .frf files to me?

My understanding is that;

FRF files are ZIP files containing either SGO (binary flash data) or ODX data.

The are encrypted with an XOR Cipher.

Once decrypted the extracted SGO file is also encrypted and compressed?

Where are the encryption and compression algorithms stored for the SGO? Are these contained within the flash memory of the ECU that the sgo is for?

I would like to read the metadata contained with the SGO.

An example for the FRF decryption: https://github.com/bri3d/VW_Flash/blob/master/frf/decryptfrf.py.
ODX is an XML file, which itself can contain flash data.
SGO is the predecessor of ODX, it's a fairly simple binary format, these notes should help:


It's the index at offset 2D which is probably what you're interested int.