This small tool has the purpose of allowing the decryption of all the passwords contained in the configuration files of the Zyxel security devices (ZyWALL, USG, etc).
The tool takes a configuration file as input and takes care of decrypting all the lines that contain the strings
Tests were performed on firmware versions 4.7x, 5.0 and 5.1.
A detailed description on how the tool works and the process of its creation can be found at https://security.humanativaspa.it/zyxel-firmware-extraction-and-password-analysis
If you wish you can contact me at @0x696e6f6465