There is not enough info on the web from what I have seen.
Most write ups/guides/blog-posts are like this:
They provide only the decrypt/encrypt script-tool with how to run it and nothing else
They provide the script with where to find the keys but not how he was able to locate them or the steps to do so nor where he got the signature part which is necessary for encrypting (so a one can apply that method to a bit diff version of the router)
They provide everything but the encrypting function.
So, I was never able to find a guide that I can replicate on just the same model but with a different key or signature not a single full guide.
Now let's say you have a firmware file & the config file. Knowing that you can extract the firmware files using 7-zip/binwalk or whatever, how to proceed from there to figure out the encryption of the config file?
Note that the answer doesn't have to go into much detail; just a quick walk through the steps in general is fine.