[Jellby]

Originally Posted by brewt

BasicSet.epub - epub created by calibre with embedded fonts embeddeed by above plugin and encrypted by above python script. [Keep ligatures] checked in conversion. Results below are the same before and after encryption.

As far as I know, calibre does not support font encryption/obfuscation.

Looking at the differences between your css and the one I use (which works with calibre):

Yours:

@font-face {
  font-style: normal;
  font-family: 'Minion Pro', serif;
  font-weight: normal;
  src: url(MinionPE.otf);
}

Mine:

@font-face {
  font-family: "Carolus FG";
  src: url("../fonts/CAROF___.TTF") format("truetype");
}

You could try something like:

@font-face {
  font-family: 'Minion Pro';
  src: url(MinionPE.otf) format('opentype');
}

and see if that helps.