ineptepub plug in with Calibre: How to generate .der file in linux

[supraman215]

I am using the ineptepub plug in with Calibre in linux. In the README it says I need to put the .der file into the Calibre config file. but it also says this:

Since there is no Linux version of Adobe Digital Editions, Linux users will have to obtain a keyfile through other methods and put the file in Calibre's configuration directory.

i installed ADE with WINE and got the epub file but I searched all the wine files, as well as the rest of my file system and can't find the .der file. The README also says this:

Since there is no Linux version of Adobe Digital Editions, Linux users will have to obtain a keyfile through other methods and put the file in Calibre's configuration directory.

What are the other methods to obtain a Key file?