These "key code generators" are scams. They are designed to steal personal information or install malware. The only legitimate ways to get a key are by buying the game or by receiving it as a gift from an authorized retailer. There is no magic generator.
: If you have a product key, you can add it to your Steam library by selecting euro truck simulator 1 email and activation code top
This is how the developers at SCS Software describe their firstborn title. And they are correct. These "key code generators" are scams