That's where I got the encryption key and method from back in 2015. On the 8970v1, the config.bin file is only encrypted, and not compressed. On later models, including the 9980, the config file is both encrypted and compressed (made smaller, like in a zip file, but it's not an actual zip file).
I think someone else reported that they succeeded by putting the `telnet -p 1023 -l login` bit into the wireless network name, simply using the web interface as usual. I think I tried all sorts of things like that with my 8970v1 and nothing worked, but it may work on other models with different wireless components.