Password encrypted files are used in Euro Truck Simulator 2 for several reasons:
That likely means someone is sharing a paid or private mod behind an encrypted archive. Without the password from the original sharer, . Trying to break encryption is: password encrypted file euro truck simulator 2 link
If you are looking to access or modify such a file, there are several established community tools and methods: SCS Unlocking Tools : Specialized community tools (such as SXC Extractor Password encrypted files are used in Euro Truck
There are several key reasons why ETS2 file creators and distributors use passwords: password encrypted file euro truck simulator 2 link